[国际标准]BS84-1956惠氏直螺纹规范标准
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中华人民共和国国家标准环境管理体系 规范及使用指南Environmental management systemsSpecification with guidance for use GB/T 24001-1996 idt ISO 14001:19961.范围 本标准规定了对环境管理体系的要求，使一个组织能够根据法律要求和重大环境影响信息，制定环境方针与目标。它适用于那些可为组织所控制，以及可能希望组织对其施加影响的环境因素。但它本身并未提出具体的环境表现（行为）准则。 本标准适用于任何有下列愿望的组织： a）实施、保持并改进环境管理体系； b）使自己确信能符合所声明的环境方针； c）向外界展示符合性； d）寻求外部组织对其环境管理体系的认证/注册； e）对符合本标准的情况进行自我鉴定和自我声明。 本标准中所有的要求都适用于任何一个环境管理体系。其应用程度取决于组织的环境方针、活动性质、运行条件等因素。本标准还在附录A中对如何使用本规范提供了提示性的指南。 对于本标准的任何应用，都应明确界定其范围。 注:为使用方便起见，“规范”部分和附录A中的条目采用了互相对应的序号，例如，4.3.3和A3.3的内容都是关于环境目标和指标的叙述, 4.5.4和A5.4的内容都是关于环境管理体系审核等。 2. 引用标准 目前尚无引用标准。 3. 定义 下列定义适用于本标准： 3.1 持续改进 continual improvement 强化环境管理体系的过程，目的是根据组织的环境方针，实现对整体环境表现（行为）的改进。 注:该过程不必同时发生于活动的所有方面。 3.2 环境 environment 组织运行活动的外部存在，包括空气、水、土地、自然资源、植物、动物、人，以及它们之间的相互关系。 注:从这一意义上,外部存在从组织内延伸到全球系统。 3.3 环境因素 environmental aspect 一个组织的活动、产品或服务中能与环境发生相互作用的要素。 注:重要环境因素是指具有或能够产生重大环境影响的环境因素。 3.4 环境影响 environmental impact 全部或部分地由组织的活动、产品或服务给环境造成的任何有害或有益的变化。 3.5 环境管理体系 environmental management systems 整个管理体系的一个组成部分，包括为制定、实施、实现、评审和保持环境方针所需的组织机构、计划活动、职责、惯例、程序、过程和资源。 3.6 环境管理体系审核 environmental management system audit 客观地获取审核证据并予以评价，以判断组织的环境管理体系是否符合所规定的环境管理体系审核准则的一个以文件支持的系统化验证过程，包括将这一过程的结果呈报管理者。 3.7 环境目标 environmental objective 组织依据其环境方针规定自己所要实现的总体环境目的，如可行应予以量化。 3.8 环境表现（行为） environmental performance 组织基于其环境方针、目标和指标，对它的环境因素进行控制所取得的可测量的环境管理体系结果。 3.9 环境方针 environmental policy 组织对其全部环境表现（行为）的意图与原则的声明，它为组织的行为及环境目标和指标的建立提供了一个框架。 3.10 环境指标 environmental target 直接来自环境目标，或为实现环境目标所需规定并满足的具体的环境表现（行为）要求，它们可适用于组织或其局部，如可行应予以量化。 3.11 相关方 interested party 关注组织的环境表现（行为）或受其环境表现（行为）影响的个人或团体。 3.12 组织 organization 具有自身职能和行政管理的公司、集团公司、商行、企事业单位、政府机构或社团，或是上述单位的部分或结合体，无论其是否法人团体、公营或私营。 注:对于拥有一个以上运行单位的组织，可以把一个运行单位视为一个组织。 3.13 污染预防 prevention of pollution 旨在避免、减少或控制污染而对各种过程、惯例、材料或产品的采用，可包括再循环、处理、过程更改、控制机制、资源的有效利用和材料替代等。 注:污染预防的潜在利益包括减少有害的环境影响、提高效益和降低成本。 4 环境管理体系要求 4.1 总要求 组织应建立并保持环境管理体系。本章描述了对环境管理体系的要求。 4.2 环境方针 最高管理者应制定本组织的环境方针并确保它: a) 适合于组织活动、产品或服务的性质、规模与环境影响； b) 包括对持续改进和污染预防的承诺； c) 包括对遵守有关环境法律、法规和组织应遵守的其它要求的承诺； d) 提供建立和评审环境目标和指标的框架； e) 形成文件，付诸实施，予以保持，并传达到全体员工； f) 可为公众所获取。4.3 规划（策划） 4.3.1 环境因素 组织应建立并保持一个或多个程序，用来确定其活动、产品或服务中它能够控制，或可望对其施加影响的环境因素，从中判定那些对环境具有重大影响，或可能具有重大影响的因素。组织应确保在建立环境目标时，对与这些重大影响有关的因素加以考虑。 组织应及时更新这方面的信息。4.3.2 法律与其他要求 组织应建立并保持程序，用来确定适用于其活动、产品或服务中环境因素的法律，以及其它应遵守的要求，并建立获取这些法律和要求的渠道。 4.3.3 目标和指标 组织应针对其内部每一有关职能和层次，建立并保持环境目标和指标。环境目标和指标应形成文件。 组织在建立与评审环境目标时，应考虑法律与其他要求，它自身的重要环境因素、可选技术方案、财务、运行和经营要求，以及各相关方的观点。 目标和指标应符合环境方针，并包括对预防污染的承诺。4.3.4 环境管理方案 组织应制定并保持一个或多个旨在实现环境目标和指标的环境管理方案，其中应包括： a) 规定组织的每一有关职能和层次实现环境目标和指标的职责, b) 实现目标和指标的方法和时间表。 如果一个项目涉及到新的开发和新的或修改的活动、产品或服务，就应对有关方案进行修订，以确保环境管理与该项目相适应。4.4 实施与运行 4.4.1 组织机构和职责 为便于环境管理工作的有效开展，应当对作用、职责和权限作出明确规定、形成文件，并予以传达。 管理者应为环境管理体系的实施与控制提供必要的资源，其中包括人力资源和专项技能、技术以及财力资源。 组织的最高管理者应指定专门的管理者代表，无论他（们）是否还负有其他方面的责任，应明确规定其作用、职责和权限，以便： a) 确保按照本标准的规定建立、实施与保持环境管理体系要求； b) 向最高管理者汇报环境管理体系的运行情况以供评审,并为环境管理体系的改进提供依据。4.4.2 培训、意识与能力 组织应确定培训的需求。应要求其工作可能对环境产生重大影响的所有人员都经过相应的培训。 应建立并保持一套程序，使处于每一有关职能与层次的人员都意识到： a) 符合环境方针与程序和符合环境管理体系要求的重要性； b) 他们工作活动中实际的或潜在的重大环境影响，以及个人工作的改进所带来的环境效益； c) 他们在执行环境方针与程序，实现环境管理体系要求，包括应急准备与响应要求方面的作用与职责； d) 偏离规定的运行程序的潜在后果。 从事可能产生重大环境影响的工作的人员应具备适当的教育、培训和（或）工作经验，从而胜任他所担负的工作。4.4.3 信息交流 组织应建立并保持一套程序，用于有关其环境因素和环境管理体系的 a) 组织内各层次和职能间的内部信息交流； b) 与外部相关方联络的接收、文件形成和答复。 组织应考虑对涉及重要环境因素的外部联络的处理，并记录其决定。4.4.4 环境管理体系文件 组织应以书面或电子形式建立并保持下列信息： a) 对管理体系核心要素及其相互作用的描述； b) 查询相关文件的途径。4.4.5 文件控制 组织应建立并保持一套程序，以控制本标准所要求的所有文件，从而确保： a) 文件便于查找； b) 对文件进行定期评审，必要时予以修订并由受权人员确认其适宜性； c) 凡对环境管理体系的有效运行具有关键作用的岗位，都可能得到有关文件的现行版本； d) 迅速将失效文件从所有发放和使用场所撤回，或采取其他措施防止误用； e) 对出于法律和（或）保留信息的需要而留存的失效文件予以标识。 所有文件均须字迹清楚，注明日期（包括修订日期），标识明确，妥善保管，并在规定期间内予以留存。应规定并保持有关建立和修改各种类型文件的程序与职责。4.4.6 运行控制 组织应根据其方针、目标和指标，确定与所标识的重要环境因素有关的运行与活动。应针对这些活动（包括维护工作）制定计划，确保它们在程序规定的条件下进行。程序的建立应符合下述要求： a) 对于缺乏程序指导可能导致偏离环境方针和目标与指标的运行，应建立并保持一套以文件支持的程序； b) 在程序中对运行标准予以规定； c) 对于组织所使用的产品和服务中可标识的重要环境因素，应建立并保持一套管理程序，并将有关的程序与要求通报供方和承包方。4.4.7 应急准备和响应 组织应建立并保持一套程序，以确定潜在的事故或紧急情况，做出响应，并预防或减少可能伴随的环境影响。 必要时，特别是在事故或紧急情况发生后，组织应对应急准备和响应的程序予以评审和修订。 可行时，组织还应定期试验上述程序。4.5 检查和纠正措施 4.5.1 监测和测量 组织应建立并保持一套以文件支持的程序，对可能具有重大环境影响的运行与活动的关键特性进行例行监侧和测量。其中应包括对环境表现、有关的运行控制、对组织环境目际和指标符合情况的跟踪信息进行记录。 监测设备应予校准并妥善维护，并根据组织的程序保存校准与维护记录。 组织应建立并保持一个以文件支持的程序，以定期评价对有关环境法律、法规的遵循情况。4.5.2 不符合，纠正与预防措施 组织应建立并保持一套程序，用来规定有关的职责和权限，对不符合进行处理与调查，采取措施减少由此产生的影响，采取纠正与预防措施并予完成。 任何旨在消除已存在和潜在不符合的原因的纠正或预防措施，应与该问题的严重性和伴随的环境影响相适应。 对于纠正与预防措施所引起对程序文件的任何更改，组织均应遵照实施并予以记录。4.5.3 记录 组织应建立并保持一套程序，用来标识、保存与处置有关环境管理的记录。这些记录中还应包括培训记录和审核与评审结果。 环境记录应字迹清楚，标识明确，具备对相关活动、产品或服务的可追溯性。对环境记录的保存和管理应使之便于查阅，避免损坏、变质或遗失。应规定其保存期限并予记录。 组织应保存记录，在对其体系及自身适宜时，用来证明符合本标准的要求。4.5.4 环境管理体系审核 组织应制定并保持用于定期开展环境管理体系审核的一个或多个方案和一些程序，进行审核的目的是： a) 判定环境管理体系： 1)是否符合对环境管理工作的预定安排和本标准的要求； 2)是否得到了正确的实施和保持。 b) 向管理者报送审核结果。 组织的审核方案（包括时间表）的制定，应立足于所涉及活动的环境重要性和以前审核的结果。为全面起见，审核程序中应包括审核的范围、频次和方法，以及实施审核和报告结果的职责与要求。4.6 管理评审 组织的最高管理者应按其规定的时间间隔，对环境管理体系进行评审，以确保体系的持续适用性、充分性和有效性。管理评审过程应确保收集必要的信息，以供管理者进行评价工作。评审工作应形成文件。 管理评审应根据环境管理体系审核的结果、不断变化的客观环境和持续改进的承诺，指出对方针、目标以及环境管理体系的其他要素加以修正的可能的需要。附录A（提示的附录）规范使用指南本附录对“要求”作了进一步说明，以防止对“规范”的错误解释。本附录仅涉及第4章中所述的关于“要求”的内容。 A1 总要求 实施“规范”所规定的环境管理体系的目的，是改进环境表现（行为）。“规范”立足于这样一个基本概念，即组织将定期评审与评价其环境管理体系，以寻求对它进行改进的可能性并予以实施。而对环境管理体系的改进，是为了实现环境表现（行为）的进一步改进。 环境管理体系为持续改进的实现提供了一个结构化的过程，改进的程度和范围由组织根据其经济状况和其他客观条件自行决定。尽管可以期望通过采用系统化的方法，实现环境表现（行为）上的某些改进，但应当认识到，环境管理体系毕竟只是一种工具，其作用是帮助组织去实现和系统地控制它自己设定的环境表现（行为）水准。环境管理体系的建立与运行，本身并不必然地导致立即降低有害环境影响的结果。 是在整个组织内，还是仅在一些特定的工作部门或活动中实施本标准，可由组织自行决定。如果仅在特定的工作部门或活动中实施，可以采纳组织内其他部分业已建立的方针和程序，用来满足本标准的要求，只要它们适用于行将采用本标准的这些特定部门或活动。环境管理体系的详尽与复杂程度，文件提供的程度，支持体系运行的资源，都取决于组织的规模及其所从事活动的性质，对于中小型企业尤其如此。 把环境事务纳入整个管理体系，将有助于环境管理体系的有效实施，同时有助于提高效能，明确责任。 本标准规定的管理体系要求，是建立在一个由“计划（策划）、实施、检查、评审”诸环节构成的动态循环过程的基础上。 该体系应使组织能够： a) 制定适宜的环境方针； b) 确定其过去、当前或计划的活动、产品或服务中的环境因素，以判定其中的重大环境影响； c) 确定有关的法律、法规要求； d) 确定优先事项，建立适当的环境目标和指标； e) 建立组织机构，制定方案，以实施环境方针，实现环境目标和指标； f) 顺利开展规划（策划）、控制、监测、纠正措施、审核与评审活动，以确保对环境方针的遵循和环境管理体系的持续适宜性。 g) 根据不断变化的客观条件作出修正。A2 环境方针 环境方针是实施与改进组织的环境管理体系的推动力，具有保持和潜在改进环境表现（行为）的作用。因此，环境方针须反映最高管理者对遵循有关法律和保证持续改进的承诺。环境方针是组织建立目标和指标的基础。对方针的规定应当作到意义明确，使内、外相关方都易于理解。应当对方针进行定期评审与修订，以反映不断变化的条件和信息。方针的应用范围应当是可以明确界定的。 组织的最高管理者应规定其环境方针并将其形成文件。如果它从属于一个更大的组织，其环境方针还应符合后者的方针，并得到后者的认可。 注：最高管理者可以是对组织负有执行职责的个人或集体。 A3 规划（策划） A3.1环境因素 4.3.1提供了一个过程，组织可据此确定哪些重要环境因素应作为其的环境管理体系的优先事项。该过程应考虑到分析工作的费用和时间，以及可靠数据的可得性。可以利用出于法规或其他目的所取得的现有信息。组织还可以把他们所关心的环境因素的实际控制程度也纳入考虑范围。组织应当考虑其现行的，以及与此有关的过去的活动、产品和（或）服务所伴随的投入和产出，以确定自身的环境因素。 如果一个组织尚未建立环境管理体系，首先应当通过评审的方式来确定自己的环境状况，这样做的目的，是对组织所具有的一切环境因素予以考虑，以此作为建立环境管理体系的基础。 已实施环境管理体系的组织，可以不进行这一评审。 评审范围应覆盖下列四个关键方面： a) 法律、法规要求； b) 重要环境因素的确定； c) 对所有现行环境管理活动与程序的审查； d) 对来自以往事件调查的反馈意见的评价。 在所有情况下，都应当考虑到组织内的正常和异常运行条件，以及可能发生的紧急状态。 评审的适宜作法可包括使用调查表、面谈、直接检验和测量，利用以往审核或其他评审的结果等，应视活动性质而定。 应对涉及下列因素的工作部门的活动所伴随的重要环境因素的确定予以考虑： a) 向大气的排放； b) 向水体的排放； c) 废物管理； d) 土地污染； e) 原材料与自然资源的使用； f) 其他当地环境问题和社区性问题。 这一过程中应考虑到正常运行条件，关闭与启动时的条件，以及可合理预见的情况或紧急状态所伴随的潜在的重大环境影响。 这一过程的目的在于确定与活动，产品或服务所伴随的重大环境影响，而不要求作具体的生命周期评价。组织无须对它的每一种产品、部件和原材料投入都作出评价。他们可以从活动、产品或服务中选择出某些属类，从中确定那些最可能具有重大环境影响的因素。 对产品环境因素的控制和影响，因组织所面临的市场情况不同而有很大的差异。相对说来，组织的承包方或供方的控制作用较微弱，而由于组织负责产品的设计，它能通过这一过程明显地改变环境因素，如通过更换某种输入材料。考虑到组织在他们产品的使用和处置过程中控制作用有限，在可行时，他们应考虑建立适当的贮运与处置机制。但这一规定不意味着改变或增加组织的法律责任。A3.2法律与其他要求 组织应遵守的其他要求示例： a) 行业规范； b) 与有关机构的协定； c) 非法规性指南。 A3.3 目标和指标 凡属可行，目标均应具体，指标均应可测量，必要时应将预防措施考虑在内。 对技术的选择，可根据自身的经济条件，考虑选用效益高、成本低。适于应用的最佳可行技术。 正文中提及对组织的财务要求，不意味着组织必须采取环境成本核算。A3.4 环境管理方案 制定与执行一个或多个方案是成功实施环境管理体系的一个关键要素。方案中应说明如何实现组织的环境目标和指标，包括时间进度和负责实施环境方针的人员。方案可予细化，具体到组织运行的基本要素。方案中应包括对新活动的环境评审。 在适当和可行时，无论对现行还是新增的活动、产品或服务，方案中可包括对计划设计、生产，营销和处置的考虑。对于产品，可从设计、材料、加工、使用及最终处置等方面进行考虑。对于安装工作或工艺上的重大修改，可从计划、设计、施工、试运行、运行，以及根据组织决定的适当时间予以关闭等方面考虑。A4 实施与运行 A4.1 组织结构和职责 环境管理体系的成功实施需要组织内全体员工的承诺。因此，不能认为环境上职责仅限于环境职能部门，事实上，组织内的其他部门，如运行管理部门，人事部门等，也可以有这方面责任。 这一承诺始于最高管理者，他（们）应制定组织的环境方针并确保环境管理体系的实施。作为上述承诺的一部分，是指定专门的管理者代表，规定他（们）对实施环境管理体系的职责和权限。对于大型或复杂的组织，可以有不止一个管理者代表。对于中、小型企业，可由一个人承担这些职责。最高管理者还应确保提供环境管理体系的实施与保持所需的适当的资源。另一重要事项是妥善规定环境管理体系的关键职责，并落实到有关人员。A4.2 培训、意识和能力 组织应建立并保持一套确定培训需求的程序。同时，它还应要求代表它工作的承包方证实其员工接受过必要的培训。 管理者应对确保人员胜任性（特别是行使环境管理职能的人员）所需的经验、能力和培训水平予以确定。A4.3 信息交流 组织应实施对有关信息和相关方要求的接受、归档与答复的程序。该程序可包括与相关方的对话和对他们所关注的问题的考虑。在某些情祝下，对相关方所关注事务的答复中，可包含有关组织运行所造成的环境影响的内容。这些程序中，还应包含就应急计划和其他问题与官方机构的联络事宜。A4.4 环境管理体系文件 文件内容应足够详尽，以充分描述环境管理体系的核心要素，以及它们之间的相互作用的情况。同时，还应能指示出获取关于环境管理体系中具体运行部分的更详细信息的途径。可将环境文件纳入组织实施的其他体系的文件。不强求编制专门手册。有关文件应包括: a) 过程信息； b) 组织机构图； c) 内部标准与运行程序； d) 现场应急计划。A4.5 文件控制 4.4.5旨在确保组织对文件的建立与保持能够充分适应实施环境管理体系的需要。但组织应将主要注意力放在环境管理体系的有效实施及其环境表现（行为）上，而不应过分追求一个繁琐的文件控制系统。A4.6 运行控制 将来修订时可能会增添这方面的内容。A4.7 应急准备和响应 将来修订时可能会增添这方面的内容。A5 检查与纠正措施 A5.1 监测和测量 将来修订时可能会增添这方面的内容。A5.2 不符合、纠正和预防措施 组织在制定与保持用于调查与纠正不符合的程序时，应包含下列基本内容： a) 确定引起不符合的原因； b) 确定并实行必要的纠正措施； c) 实施或修改必要的控制措施，以防再度发生不符合； d) 记录由纠正措施所导致的对书面程序的任何更改。 根据情况的不同，有时纠正措施可能只需略为计划，并能迅速见效，但有时可能是一项复杂、长期的活动。相应的文件应与纠正措施的规模相适配。A5.3 记录 用来标识、保持与处置记录的程序，应将重点放在那些为实施与运行环境管理体系所需的和关于环境目标和指标实现程度的记录上。 环境记录可包括： a) 关于适用的环境法律与其他要求的信息； b) 投诉记录； c) 培训记录； d) 过程信息； e) 产品信息； f) 检查、维护与校准记录； g) 有关的供方与承包方信息； h) 事故报告； i) 应急准备与响应信息； j) 重要环境因素信息； k) 审核结果 l)管理评审。 应对机密业务信息的管理给以适当考虑。A5.4 环境管理体系审核 审核方案与程序应包括： a) 待审核的活动与区域； b) 审核的频次； c) 管理与实施审核的职责； d) 审核结果的通报； e) 审核员的能力； f) 如何实施审核。 审核工作可由组织内部人员或组织聘请的外部人员承担，无论哪种情况，从事审核的人员都应做到公正，客观。A6 管理评审 为了保持环境管理体系的持续改进、适用性和有效性，从而取得良好的环境表现（行为）。组织的管理者应按规定的时间间隔对环境管理体系进行评审与评价。评审范围应当全面，但不必在一次评审中涉及环境管理体系的所有要素，同时评审过程可以延续一段时间。 对方针、目标与程序的评审，应由制定它们的相应管理层承担。 评审内容应包括： a) 审核结果； b) 目标和指标的实现程度； c) 面对变化的条件与信息，环境管理体系是否具有持续的适用性； d) 相关方关注的问题。 观察结果、结论与建议应形成文件，以便采取必要的措施。文献目录1. GB/T240041996，环境管理体系 原则、体系和支持技术通用指南 2. GB/T240101996，环境审核指南 通用原则 3. GB/T240111996，环境审核指南 审核程序 环境管理体系审核 4. GB/T240121996，环境审核指南 环境审核员资格要求BRITISH STANDARDBS 84:1956Specification forParallel screw threads of Whitworth formUDC 621.882.082.2BS 84:1956This British Standard, having been approved by the Mechanical Engineering Industry Standards Committee and endorsed by the Chairman of the Engineering Divisional Council, was published under the authority of the General Council on 26 September 1956 BSI 02-2000First published as BS 84:1918and BS 92:1919First revision as BS 84 (incorporating BS 92) May 1940Second revision September 1956The following BSI references relate to the work on this standard:Committee reference MEE/1/12Draft for comment CT(MEE)6884ISBN 0 580 32662 4Co-operating organizationsThe Mechanical Engineering Industry Standards Committee, under whose supervision this British Standard was prepared, consists of representatives from the following Government departments and scientific and industrial organizations:Admiralty*Air Ministry*Associated Offices Technical CommitteeAssociation of Consulting Engineers (Incorporated)British Chemical Plant Manufacturers AssociationBritish Compressed Air SocietyBritish Electrical and Allied Manufacturers Association*British Engineers Association*British Internal Combustion Engine Manufacturers AssociationBritish Iron and Steel FederationBritish Railways, The British Transport Commission*Central Electricity Authority and Area BoardsCrown Agents for Oversea Governments and AdministrationsD.S.I.R. Mechanical Engineering Research Laboratory*Engineering Equipment Users Association*Gas CouncilHigh Commission of IndiaInstitute of Marine EngineersInstitute of PetroleumInstitution of Civil EngineersInstitution of Gas EngineersInstitution of Heating and Ventilating EngineersInstitution of Mechanical Engineers*Institution of Mechanical Engineers (Automobile Division)Institution of Production Engineers*Locomotive and Allied Manufacturers Association*Ministry of Fuel and PowerMinistry of Labour and National Service (Factory Department)Ministry of Supply*Ministry of Transport and Civil AviationMinistry of WorksNational Coal BoardNational Physical LaboratoryRadio Industry Council*War OfficeThe organizations marked with an asterisk in the above list, together with the following, were directly represented on the Committee entrusted with the preparation of this standard:Agricultural Engineers AssociationBritish Bolt, Nut, Screw and Rivet FederationCut Thread Screwing Tool Manufacturers AssociationEngineering Standards Co-ordinating CommitteeGauge and Tool Makers AssociationGround Thread Tap AssociationMachine Tool Trades AssociationNational Association of Marine Engine BuildersScientific Instrument Manufacturers AssociationSociety of British Aircraft ConstructorsSociety of Motor Manufacturers and Traders Ltd.Telecommunication Engineering and Manufacturing AssociationAmendments issued since publicationAmd. No.DateComments标准分享网 w w w .b z f x w .c o m 免费下载BS 84:1956 BSI 02-2000iContentsPageCo-operating organizationsInside front coverForewordiii1Scope12Nomenclature and definitions13Form of Whitworth screw threads14Classes of bolts and nuts15Standard diameter pitch series: limits and tolerances26Plated threads27Stainless steel bolts38Selected thread series3a) Basic sizesb) Design sizesc) Tolerances9Tolerances on effective diameter, pitch and flank angles410Designation of screw threads of Whitworth form411Gauges5Appendix A Truncated Whitworth form threads with flat crests34Appendix B Bases of tolerances and allowances for Whitworth form screw threads39Appendix C Tolerances on pitch and angle in relation to tolerance on effective diameter41Appendix D Notes on the form of the crests of Whitworth threads42Appendix E44Figure 1 Basic form of Whitworth thread6Figure 2 Effective diameter tolerance zones of recommended combinations of classes of bolts and nuts having Whitworth screw threads7Figure 3 Tolerance zones for close class bolt and medium class nut 1/4in. B.S.W. (20 t.p.i.) illustrated8Figure 4 Tolerance zones for medium class bolt with allowance and normal class nut. 1/4in. B.S.W. (20 t.p.i.) illustrated9Figure 5 Tolerance zones for free class bolt with allowance and normal class nut. 1/4in. B.S.W. (20 t.p.i.) illustrated10Figure 6 Effective diameter tolerance zones for Whitworth bolts and nuts, unplated or before plating, and after plating (cf. Figure 2) of sizes 3/4in. nominal size and smaller11Figure 7 Tolerance zones for truncated Whitworth thread 1/4 in. B.S.W. (20 t.p.i.) illustrated36Figure 8 Crest forms resulting from different production methods43Table 1 Basic sizes12Table 2 Bolts Close class13Table 3 Nuts Medium class14Table 4 Bolts Medium class15a) Nominal sizes up to and including 3/4in.b) Nominal sizes above 3/4in.Table 5 Nuts Normal class16BS 84:1956ii BSI 02-2000PageTable 6 Bolts Free class17a) Nominal sizes up to and including 3/4in.b) Nominal sizes above 3/4in.Table 7 Basic sizes18Table 8 Bolts Close class19Table 9 Nuts Medium class20Table 10 Bolts Medium class21a) Nominal sizes up to and including 3/4in.b) Nominal sizes above 3/4in.Table 11 Nuts Normal class22Table 12 Bolts Free class23a) Nominal sizes up to and including 3/4in.b) Nominal sizes above 3/4in.Table 13 Preferred diameters and pitches Fractional sizes24Table 13a Preferred diameters and pitches Decimal sizes27Table 14 Depths of thread for various pitches29Table 15 Bolts Medium and free class allowances31Table 16 Bolts Close class31Table 17 Nuts Medium class32Table 18 Bolts Medium class32Table 19 Nuts Normal class33Table 20 Bolts Free class33Table 21 Basic data37Table 22 Bolts and nuts all classes38Table 23 Bolts and nuts all classes39Table 24 Nuts Close class44Table 25 Nuts Close class45Table 26 Nuts Close class46标准分享网 w w w .b z f x w .c o m 免费下载BS 84:1956 BSI 02-2000iiiForewordThis standard makes reference to the following British Standards:BS 919, Screw gauge limits and tolerances. BS 1157, Tapping drill sizes. BS 1916, Pt. 2. Guide to the selection of fits. BS 2517, Definitions for use in mechanical engineering. This revised British Standard has been prepared, under the authority of the Mechanical Engineering Industry Standards Committee, to supersede BS 84:1940, “Screw threads of Whitworth form”. It applies to threads of Whitworth form used for general engineering purposes and is not intended to apply to special applications such as those requiring interference fits.The standard includes tables of basic sizes, limits and tolerances for British Standard Whitworth (B.S.W.) and British Standard Fine (B.S.F.) screw threads. In addition it now provides a “Selected Thread” series of recommended diameter-pitch combinations for use in applications where the standard coarse (B.S.W.) and fine (B.S.F.) pitch series have insufficiently fine pitches.The British Standard Pipe parallel thread series was incorporated in BS 84:1940 as a fine thread series for general engineering purposes, and though this series was not intended for pipe joints it has been extensively used on certain types of pipe fittings, such as unions, compression type connections, etc., where the pressure seal is not made on the threads. This has caused some confusion with the pipe threads specified in BS 211) where the pressure seal is, in fact, made on the threads. It has, therefore, been decided to publish the tables of basic sizes, limits and tolerances for the British Standard Pipe parallel thread series given in BS 84:1940 in a new standard, BS 2779, “Fastening Threads of B.S.P. Sizes,” now in course of preparation. This standard, in addition to BS 21, which is now being revised, will come under the aegis of the Pipe Threads Committee of BSI and these two standards will then include recommended limits and tolerances for all B.S.P. threads whether or not the pressure seal is made upon the threads.The new “Selected Thread” series will, in most cases, be more suitable for use in new designs than the BS Pipe parallel thread series in cases where an extra fine pitch thread is required, and its use is strongly recommended.In revising this standard, advantage has been taken of the experience gained in the use of BS 84:1940, to modify it to conform to modern thread tolerancing practice. Thus an allowance (minimum clearance) is provided on certain classes of bolts of sizes up to and including3/4in. diameter; the recommended associations of classes of bolts and nuts include nuts having larger effective diameter tolerances than the corresponding sizes of bolts. Three classes of tolerance are provided for bolts, the Close, Medium and Free Classes, equivalent to the old Close, Medium and Free Fit bolts. The allowance is provided on bolts in the Medium and Free Classes by reducing the maximum bolt limits below basic size. The purpose of this allowance is to provide for the threads to be plated if necessary, the plating encroaching within the allowance; it also guarantees easy assembly of maximum metal bolts and nuts, thus facilitating the use of torque wrenches. Two classes of tolerance for nuts are recommended, a Medium Class and Normal Class, identical with the old Medium and Free Fit nuts respectively. The old Close Fit (now termed Close Class) nuts, are now regarded as non-preferred but, in view of their usage in the past and for special needs, their limits and tolerances are given in an Appendix to the standard.All screw threads made in accordance with this revised standard will assemble with the corresponding nominal sizes of mating screw threads made to BS 84:1940.1) BS 21, “Pipe threads”.BS 84:1956iv BSI 02-2000It will be observed that no change has been made in the general three-part formula used as a basis for tolerancing effective diameters, and the formulae used for tolerancing the other thread elements also remain unchanged from those in BS 84:1940; the reason for this is to minimize any changes in the sizes of the gauges used to control the size of the finished work.The table of recommended diameter-pitch combinations for screw threads in the “Selected Thread” series follows very closely the corresponding Table in BS 1580, “Unified Screw Threads”.In revising the standard the following amendments issued subsequent to BS 84:1940 have been incorporated in the text, with the exception of that part of the amendments dealing with B.S.P. threads, and Amendments Nos. 1 and 2 have been restricted to lengths of engagement of bolt and nut up to 15 pitches.Amendment No. 1, June 1942, provided simplified tables of tolerances for threads not in the three standard diameter-pitch series (B.S.W., B.S.F. and B.S.P.), based on a length of engagement of bolt and nut of 10 pitches, but applicable in practice to all reasonable lengths of engagement.Amendment No. 2, April 1943, specified that the tolerances given in the three standard diameter-pitch series should apply to all lengths of engagement.Amendment No. 3, August 1945, provided information about truncated Whitworth form screw threads.Amendment No. 4, December 1949, gave extensions of tables of limits and tolerances for the larger sizes of standard diameter-pitch combinations of Whitworth form.In conclusion it may be asked why the revision of this standard has been undertaken in view of the standardization of the Unified thread in BS 1580. The reason is that Whitworth threads will undoubtedly continue to be used for many years, especially on replacements or spare parts.A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application.Compliance with a British Standard does not of itself confer immunity from legal obligations.Summary of pagesThis document comprises a front cover, an inside front cover, pages i to iv, pages 1 to 47 and a back cover.This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.标准分享网 w w w .b z f x w .c o m 免费下载BS 84:1956 BSI 02-200011 ScopeThis British Standard relates to parallel screw threads, having the Whitworth form of thread, used for general engineering purposes. It is not intended to apply to threaded pipe joints, screw threads associated with interference fits, such as those on the “metal-ends” of studs and in the corresponding tapped holes, or to screw threads which are subject to high temperature.This standard includes:a) A coarse thread series, the British Standard Whitworth (B.S.W.) Series, from 1/8in. to 6 in. diameter.b) A fine thread series, the British Standard Fine (B.S.F.) Series, from 3/16in. to 41/4in. diameter.NOTEThe tables of limits and tolerances in the B.S.F. Series extend up to the 3 in. size only, since nominal sizes above 3 in. are rarely used.c) A supplementary Selected Thread Series from 1/4in. diameter upwards.d) Screw threads of Truncated Whitworth form (Appendix A). Supplementary information is given in Appendix A to Appendix E.2 Nomenclature and definitionsFor the nomenclature and definitions of terms used in this standard, see BS 2517, “Definitions for use in Mechanical Engineering”.3 Form of Whitworth screw threadThe basic (and design) form of the Whitworth thread is shown in Figure 1. It is a symmetrical V-thread in which the angle between the flanks, measured in an axial plane, is 55; one-sixth of the sharp vee is truncated at top and bottom, the thread being rounded equally at crests and roots by circular arcs blending tangentially with the flanks, the theoretical depth of thread being thus 0.640327 times the nominal pitch.The basic thread depths calculated from the above definition are rounded off to the nearest 0.0001 in.4 Classes of bolts and nutsThree classes of tolerances for bolts and two classes for nuts2) are provided as follows:Close class bolts. The close class3) applies to screw threads requiring a fine snug fit, obtainable consistently only by the use of the highest quality production equipment supported by a particularly efficient system of gauging and inspection. It should be used only for special work where refined accuracy of pitch and thread form are particularly required.Medium class bolts and nuts. The medium class applies to the better class of ordinary interchangeable screw threads.Free class bolts. The free class applies to the majority of bolts of ordinary commercial quality.Normal class nuts. The normal class applies to ordinary commercial quality nuts; this class is intended for use with medium or free class bolts.The relative magnitudes and dispositions of the effective diameter tolerance zones4) for the recommended combinations of classes are shown in Figure 2.It will be noted that the lower limit of the nut is always basic size. No allowance is provided for close class bolts, but for medium and free class bolts an allowance is provided between the lower limit for the nut (basic size) and the upper limit for the bolt on sizes 3/4in. nominal diameter and below. The allowance amounts to 0.3 medium class bolt effective diameter tolerance for nominal sizes of 3/4in. down to 1/4in. The allowance for nominal sizes less than 1/4in. is the same as that for the 1/4in. size.Since it is more difficult to control the threading of nuts than bolts the recommended classes of nuts to be associated with close and medium class bolts have effective diameter tolerances 50 per cent greater than those of the associated bolts.2) The terms “bolts” and “nuts” are used in a general sense to designate external and internal threads respectively.3) Limits and tolerances for close nuts are given in Appendix E.4) For the bases of the tolerances and allowances see Appendix B.BS 84:19562 BSI 02-2000The choice of fit for a particular purpose rests with the designer. A close class bolt would usually be assembled with a medium class nut, and a medium or free class bolt with a normal class nut, but in special circumstances different combinations of classes may be specified for mating bolts and nuts if desired.Information about plating, as applied to the various classes of bolts and nuts, is given in Clause 6.5 Standard diameter pitch series: Limits and tolerancesThe basic sizes for the B.S.W. and B.S.F. series are given in Table 1 and Table 7 respectively.Limits and tolerances for the major, effective and minor diameters for the various classes are given in Table 2 to Table 6 for the B.S.W. series and in Table 8 to Table 12 for the B.S.F. series. Limits and tolerances for close class nuts in the B.S.W. and B.S.F. series are given in Appendix E.In these tables, the effective diameter tolerances, which are intended to include the diametral effects of pitch and angle error (see Appendix C), have been calculated from the general formula (see page 40) taking the length of engagement as being equal to the nominal diameter of the thread. In order to reduce to a minimum the number of NOT GO gauges required, the tolerances for the B.S.W. and B.S.F. series of threads, although calculated for the lengths of engagement just quoted may, however, be regarded as applicable to lengths of engagement up to fifteen pitches. The tolerances quoted for the major and minor diameters of threads belonging to the B.S.W. and B.S.F. series may be accepted for any length of engagement.Following existing practice, no tolerance is specified for the major diameters of the nuts, but only a minimum size, which is the same as the basic major diameter. The major diameters of nuts will be controlled in practice by the major diameters of the taps or other screwing tools used to cut the threads.Figure 3, Figure 4 and Figure 5 show, for the three recommended combinations of classes respectively, the relationship existing between the diametral tolerances for a 1/4in. B.S.W. bolt and nut. It will be noted that the nut minor diameter tolerances are such as to permit a tapping drill of ample size to be used, thus preventing binding at the root of the tap during the tapping operation. If full advantage is taken of the generous nut minor diameter tolerances, the crests of the nut threads will be flat. In special cases, though, where thin nuts are used, it may be desirable not to take full advantage of the tolerance on minor diameter. It will also be noted that the bolt major diameter tolerances are such as to permit crests which are not perfectly radiused (see Appendix D).Formulae for calculating the tolerances for major, effective and minor diameters are given in Appendix B.6 Plated threadsThe following recommendations refer to the limits for screw threads which are plated with metals such as cadmium, nickel, tin or zinc, where the usual thickness of plating is of the order of 0.0002 in.; they do not apply to heavily plated threads.Taking as a basis Figure 2, which shows the effective diameter tolerance zones for bolts and nuts of the various classes supplied unplated, Figure 6 shows in addition the corresponding recommended tolerance zones for bolts and nuts of nominal sizes 3/4in. and below before and after plating.It will be noted for these sizes that plating is accommodated within the allowance in the case of the medium and free class bolts, and by adjustment of the bolt tolerance zone in the case of the close class bolts.The interpretation of Figure 6 is as follows:i) Both free and medium class bolts are suitable for plating. The finished size of the screw threads after plating shall not exceed the basic size.ii) Should it be necessary to plate close class bolts, again the finished size of the threads after plating shall not exceed the basic size. In order to avoid any undue restriction of the tolerance for screwing, the sizes of close class bolts before plating may be smaller than the lower limits specified in Table 2 and Table 8 by an amount not greater than 0.001 in.iii) The sizes of finished medium class and normal class nuts, whether plated or not, shall not fall below the lower limits specified in the appropriate tables of limits and tolerances.iv) Since the plating of medium class nuts may necessitate a reduction in the manufacturing tolerances in order that, after plating, they comply with the specified lower limits, it is strongly recommended that plated normal class nuts be used instead of medium class where plating is a requirement.标准分享网 w w w .b z f x w .c o m 免费下载BS 84:1956 BSI 02-20003Bolts and nuts of nominal sizes above 3/4in., whether plated or not, shall comply with the limiting sizes specified in the appropriate tables with the following exception. In order to avoid any undue restriction of the tolerance for screwing, the sizes of close class bolts before plating may be smaller than the lower limits specified in the tables by an amount not greater than 0.001 in.Where it is known that nuts will be plated, care should be taken that the nuts are made with minimum sizes slightly greater than basic size in order to effect satisfactory assembly after plating. Similarly, medium and free class bolts of nominal sizes above 3/4in. diameter, which are required to be plated, should be made with maximum sizes slightly less than basic size.The above remarks apply not only to the tolerance zones for effective diameter, but equally to the tolerance zones for the major and minor diameters of plated threads. The limiting sizes of medium and free class B.S.W. and B.S.F. bolt threads before and after plating are indicated in Table 4, Table 6, Table 10 and Table 12 respectively.Recommendations on the gauging of plated screw threads are given in an Appendix to BS 919, “Screw gauge limits and tolerances”.7 Stainless steel boltsOwing to the tendency for close-fitting bolts and nuts of stainless steel to seize when tightened together, it is recommended that stainless steel bolts of nominal sizes 3/4in. and below should not be made to close class limits but rather to medium or free class limits for unplated bolts. It is recommended that stainless steel bolts of nominal sizes above 3/4in. shall have maximum and minimum limits which are 0.001 in. smaller than the values obtained from the tables.8 Selected thread seriesRecommended diameter-pitch combinations for the applications of threads of Whitworth form, for which the B.S.W. and B.S.F. diameter-pitch series are unsuitable, are given in Table 13 and Table 13A.Two tables of preferred diameters and associated pitches are included to meet the needs of different sections of industry, some preferring to use common fractions and others decimals. Table 13 lists the fractional, and Table 13A the decimal series. It will be noted that both tables contain, above 11/2in. diameter, the same 1/4in. and 1/2in. steps, the difference between the two tables being that in the decimal series the intermediate 1/8in. steps have been replaced by steps to the nearest 1/10in. dimension. This enables the same diameters to be used as are recommended in BS 1916-25).a) Basic sizes. The basic effective and minor diameters may be determined by subtracting from the basic major diameter the basic depth of thread and twice the basic depth of thread respectively (Columns 3 and 4, Table 14).b) Design sizes. i) Nuts. The design sizes of the major, effective and minor diameters for all classes are the same as the corresponding basic sizes.ii) Bolts. A. Close class. The design sizes are the same as the basic sizes.B. Medium and free classes. Basic major diameters of 3/4in. and below. The design sizes are obtained from the basic sizes by subtracting the appropriate allowance given in Table 15.Basic major diameters above 3/4in. The design sizes are the same as the basic sizes.c) Tolerances. The tolerances on Whitworth Selected Threads for bolts and nuts of nominal sizes up to 20 in. are obtained from Table 16 to Table 20 inclusive. For nominal diameters above 20 in. the tolerances should be calculated from the data and formulae in Appendix B.The effective diameter tolerances have been calculated from the general formula given in Appendix B, assuming a length of engagement of the mating threads equal to ten times the pitch. The tolerances so obtained may be regarded as satisfactory for all normal lengths of engagement, say five to fifteen pitches. For exceptional lengths of engagement, if these tolerances are found to be unsuitable, the effective diameter tolerance should be calculated from the basic formula in Appendix B, giving Le its actual value.5) BS 1916-2, “Guide to the selection of fits”.BS 84:19564 BSI 02-2000No tolerance is specified for the major diameter of the nut thread, as it is considered that this dimension will be controlled adequately by the crests of the taps or other cutting tools used to produce the threads.All diametral tolerances on screw threads are applied unilaterally from the appropriate design size of the dimension, “minus” for a bolt and “plus” for a nut.Examples illustrating the use of Table 14 to Table 20 when determining limits and tolerances of Whitworth Selected Screw Threads are given following Table 14.Exceptional design requirements may, at times, necessitate the use of a screw thread of Whitworth form but having a diameter-pitch combination differing from those recommended in Table 13 and Table 13A and the relevant notes. It is recommended in such cases that the number of threads per inch should be chosen from the following series.40 36 32 28 26 24 20 18 16 14 12 11 10 8 6 4 threads per inchThe numbers of threads per inch in heavy type are to be regarded as preferred.The design sizes and tolerances for such threads should be derived as stated for threads in the Selected Thread series.9 Tolerances on effective diameter, pitch and flank anglesErrors in the pitch and flank angles of a thread virtually increase the effective diameter of a bolt and decrease the effective diameter of a nut. The minimum metal limits stated in the tables apply to the simple effective diameter (as measured along the pitch line of the thread) and the maximum metal limits apply to the effective diameter as virtually increased (for bolts) or decreased (for nuts) by the diametral equivalents of any errors present in the flank angles and in the pitch over the length of engagement (see Appendix C).10 Designation of screw threads of Whitworth formIt is recommended that the following system should be adopted on drawings and related documents for designating the screw threads covered by the present standard.The basic major diameter of the thread and the number of threads per inch should be added to the designation. If the thread is left-hand the symbol “LH” should follow the designation.Examples:1/4in. 20 B.S.W.1/2in. 16 B.S.F., LHFor screw threads of the selected diameters and pitches given in Table 13 and Table 13A, the basic major diameter and number of threads per inch should be stated, followed by the symbol “Whit. S”.Example: 1 in. 20 Whit. S.Screw threads of Whitworth form but not having the selected diameter-pitch combinations given in Table 13 and Table 13A should be designated as given below:Example: 0.67 in. 20 Whit.Where it is desired to designate the class of thread tolerance, one of the four terms “close”, “medium”, “free” or “normal” should be added in brackets, together with the word ”bolt” or “nut” as appropriate.Examples:1/4in. 20 B.S.W. (close) bolt.1 in. 20 Whit. S. (free) bolt.11/2in. 8 B.S.F. (normal) nut.It is recommended that multiple-start Whitworth form threads should be designated as in the following example:2 in. 2 start, 0.2 in. lead, 0.1 in. pitch, Whit.DesignationBritish Standard Whitworth seriesB.S.W.British Standard Fine seriesB.S.F.标准分享网 w w w .b z f x w .c o m 免费下载BS 84:1956 BSI 02-2000511 GaugesIt is recommended that the gauging system to be employed for checking screw threads of Whitworth form between the limits laid down in this standard should be that given in BS 919, “Screw gauge limits and tolerances”.Unless otherwise stated GO ring or calliper gauges for medium or free class bolts of nominal sizes 3/4in. and below will be supplied made to the limits for unplated bolts.BS 84:1956 BSI 02-20006Figure 1 Basic form of Whitworth thread标准分享网 w w w .b z f x w .c o m 免费下载BS 84:1956 BSI 02-20007NOTE 1The Medium Class bolt effective diameter tolerance is shown as 100 units and the other values are expressed as a percentage of this tolerance. The formula for effective diameter tolerance is given in Appendix B.NOTE 2See Appendix E for Close Class nuts for special needs.* See Clause 4.Figure 2 Effective diameter tolerance zones of recommended combinations of classes of bolts and nuts having Whitworth screw threadsBS 84:19568 BSI 02-2000Figure 3 Tolerance zones for close class bolt and medium class nut 1/4in. B.S.W. (20 t.p.i.) illustrated标准分享网 w w w .b z f x w .c o m 免费下载BS 84:1956 BSI 02-20009NOTEThe maximum bolt dimensions refer to unplated bolts only.Figure 4 Tolerance zones for medium class bolt with allowance and normal class nut. 1/4in. B.S.W. (20 t.p.i.) illustratedBS 84:195610 BSI 02-2000NOTEThe maximum bolt dimensions refer to unplated bolts only.Figure 5 Tolerance zones for free class bolt with allowance and normal class nut. 1/4in. B.S.W. (20 t.p.i.) illustrated标准分享网 w w w .b z f x w .c o m 免费下载BS 84:1956 BSI 02-200011NOTE 1Bolt Medium Class effective diameter tolerance is shown as 100 units.NOTE 2See Appendix E for Close Class nuts for special needs.Figure 6 Effective diameter tolerance zones for Whitworth bolts and nuts, unplated or before plating, and after plating (cf. Figure 2) of sizes 3/4in. nominal size and smallerBS 84:195612 BSI 02-2000Coarse thread series, B.S.W.Table 1 Basic sizes12345678Nominal sizeNumber of threads per inchPitchDepth of threadMajor diameterEffective diameterMinor diameterCross sectional area at bottom of threadin.in.in.in.in.in.sq. in.1/8ab3/161/44024200.025000.041670.050000.01600.02670.03200.12500.18750.25000.10900.16080.21800.09300.13410.18600.00680.01410.02725/163/87/161816140.055560.062500.071430.03560.04000.04570.31250.37500.43750.27690.33500.39180.24130.29500.34610.04570.06830.09411/29/16a5/81212110.083330.083330.090910.05340.05340.05820.50000.56250.62500.44660.50910.56680.39320.45570.50860.12140.16310.203211/16a3/47/8111090.090910.100000.111110.05820.06400.07110.68750.75000.87500.62930.68600.80390.57110.62200.73280.25620.30390.4218111/811/48770.125000.142860.142860.08000.09150.09151.00001.12501.25000.92001.03351.15850.84000.94201.06700.55420.69690.894211/213/42654.50.166670.200000.222220.10670.12810.14231.50001.75002.00001.39331.62191.85771.28661.49381.71541.30001.75302.311021/421/223/4443.50.250000.250000.285710.16010.16010.18302.25002.50002.75002.08992.33992.56701.92982.17982.38402.92503.73204.4640331/4a31/50.285710.307690.307690.18300.19700.19703.00003.25003.50002.81703.05303.30302.63402.85603.10605.44906.40607.577033/4a441/2332.8750.333330.333330.347830.21340.21340.22273.75004.00004.50003.53663.78664.27733.32323.57324.05468.674010.030012.9100551/262.752.6252.50.363640.380950.400000.23280.24390.25615.00005.50006.00004.76725.25615.74394.53445.01225.487816.150019.730023.6500a To be dispensed with wherever possible.b Dimensionally, the 1/8 in. 40 t.p.i. thread belongs more appropriately to the B.S.F. series, but it has for so long been associated with the B.S.W. series that it is now included herein.标准分享网 w w w .b z f x w .c o m 免费下载BS 84:1956 BSI 02-200013Table 2 Bolts Close classLimits and Tolerances1234567891011Nominal sizeNumber of threads per in.Major diameterEffective diameterMinor diameterMax.Tol.Min.Max.Tol.Min.Max.Tol.Min.in.in.in.in.in.in.in.in.in.in.1/8a3/161/44024200.12500.18750.25000.00350.00430.00480.12150.18320.24520.10900.16080.21800.00190.00230.00260.10710.15850.21540.09300.13410.18600.00400.00500.00550.08900.12910.18055/163/87/161816140.31250.37500.43750.00520.00550.00590.30730.36950.43160.27690.33500.39180.00280.00300.00320.27410.33200.38860.24130.29500.34610.00590.00620.00670.23540.28880.33941/29/16a5/81212110.50000.56250.62500.00630.00650.00670.49370.55600.61830.44660.50910.56680.00340.00360.00370.44320.50550.56310.39320.45570.50860.00720.00740.00760.38600.44830.501011/16a3/47/8111090.68750.75000.87500.00680.00720.00760.68070.74280.87640.62930.68600.80390.00380.00400.00430.62550.68200.79960.57110.62200.73280.00770.00810.00860.56340.61390.7242111/811/48771.00001.12501.25000.00800.00860.00870.99201.11641.24130.92001.03351.15850.00450.00480.00490.91551.02871.15360.84000.94201.06700.00910.00970.00980.83090.93231.057211/213/42654.51.50001.75002.00000.00940.01020.01081.49061.73981.98921.39331.62191.85770.00530.00570.00611.38801.61621.85161.28661.49381.71540.01060.01150.01221.27601.48231.703221/421/223/4443.52.25002.50002.75000.01140.01160.01232.23862.48842.73772.08992.33992.56700.00640.00660.00702.08352.33332.56001.92982.17982.38400.01290.01310.01391.91692.16672.3701331/4a31/53.00003.25003.50000.01250.01300.01322.98753.23703.48682.81703.05303.30300.00720.00740.00762.80983.04563.29542.63402.85603.10600.01410.01460.01482.61992.84143.091233/4a441/2332.8753.75004.00004.50000.01360.01380.01433.73643.98624.48573.53663.78664.27730.00790.00800.00843.52873.77864.26893.32323.57324.05460.01540.01550.01613.30783.55774.0385551/262.752.6252.55.00005.50006.00000.01480.01530.01584.98525.48475.98424.76725.25615.74390.00880.00910.00944.75845.24705.73454.53445.01225.48780.01660.01710.01774.51784.99515.4701a To be dispensed with wherever possible.BS 84:195614 BSI 02-2000Table 3 Nuts Medium classLimits and Tolerances123456789Nominal sizeNumber of threads per inchMajor diameterEffective diameterMinor diameterMin.Max.Tol.Min.Max.Tol.Min.in.in.in.in.in.in.in.in.1/8a3/161/44024200.12500.18750.25000.11190.16430.22190.00290.00350.00390.10900.16080.21800.10200.14740.20300.00900.01330.01700.09300.13410.18605/163/87/161816140.31250.37500.43750.28110.33950.39660.00420.00450.00480.27690.33500.39180.25940.31450.36740.01810.01950.02130.24130.29500.34611/29/16a5/81212110.50000.56250.62500.45180.51440.57240.00520.00530.00560.44660.50910.56680.41690.47940.53380.02370.02370.02520.39320.45570.508611/16a3/47/8111090.68750.75000.87500.63510.69200.81030.00580.00600.00640.62930.68600.80390.59630.64900.76200.02520.02700.02920.57110.62200.7328111/811/48771.00001.12501.25000.92681.04071.16590.00680.00720.00740.92001.03351.15850.87200.97761.10260.03200.03560.03560.84000.94201.067011/213/42654.51.50001.75002.00001.40131.63051.86680.00800.00860.00911.39331.62191.85771.32691.54081.76680.04030.04700.05141.28661.49381.715421/421/223/4443.52.25002.50002.75002.09952.34992.57740.00960.01000.01042.08992.33992.56701.98682.23682.44810.05700.05700.06411.92982.17982.3840331/4a31/53.00003.25003.50002.82783.06413.31440.01080.01110.01142.81703.05303.30302.69812.92453.17450.06410.06850.06852.63402.85603.106033/4a441/2332.8753.75004.00004.50003.54843.79874.28990.01180.01210.01263.53663.78664.27733.39693.64694.13120.07370.07370.07663.32323.57324.0546551/262.752.6252.55.00005.50006.00004.78035.26985.75800.01310.01370.01414.76725.25615.74394.61415.09545.57480.07970.08320.08704.53445.01225.4878a To be dispensed with wherever possible.标准分享网 w w w .b z f x w .c o m 免费下载BS 84:1956 BSI 02-200015Table 4 Bolts Medium classLimits and Tolerancesa) Nominal sizes up to and including 3/4 in.1234567891011121314Nominal sizeNumber of threads per inchMajor diameterEffective diameterMinor diameterUnplated or before platingAfter platingUnplated or before platingAfter platingUnplated or before platingAfter platingMax.Tol.Min.Max.Max.Tol.Min.Max.Max.Tol.Min.Max.in.in.in.in.in.in.in.in.in.in.in.in.in.1/8a3/161/44024200.12380.18630.24880.00450.00550.00610.11930.18080.24270.12500.18750.25000.10780.15960.21680.00290.00350.00390.10490.15610.21290.10900.16080.21800.09180.13290.18480.00610.00760.00840.08570.12530.17640.09300.13410.18605/163/87/161816140.31120.37360.43600.00660.00700.00750.30460.36660.42850.31250.37500.43750.27560.33360.39030.00420.00450.00480.27140.32910.38550.27690.33500.39180.24000.29360.34460.00890.00950.01010.23110.28410.33450.24130.29500.34611/29/16a5/81212110.49850.56090.62330.00810.00820.00860.49040.55270.61470.50000.56250.62500.44510.50750.56510.00520.00530.00560.43990.50220.55950.44660.50910.56680.39170.45410.50690.01100.01110.01160.38070.44300.49530.39320.45570.508611/16a3/411100.68580.74820.00880.00920.67700.73900.68750.75000.62760.68420.00580.00600.62180.67820.62930.68600.56940.62020.01180.01230.55760.60790.57110.6220b) Nominal sizes above 3/4 in.1234567891011Nominal sizeNumber of threads per in.Major diameterEffective diameterMinor diameterMax.Tol.Min.Max.Tol.Min.Max.Tol.Min.in.in.in.in.in.in.in.in.in.in.7/8111/89870.87501.00001.12500.00970.01030.01100.86530.98971.11400.80390.92001.03350.00640.00680.00720.79750.91321.02630.73280.84000.94200.01310.01390.01480.71970.82610.927211/411/213/47651.25001.50001.75000.01120.01210.01311.23881.48791.73691.15851.39331.62190.00740.00800.00861.15111.38531.61331.06701.28661.49380.01500.01620.01751.05201.27041.4763221/421/24.5442.00002.25002.50000.01380.01460.01501.98622.23542.48501.85772.08992.33990.00910.00960.01001.84862.08032.32991.71541.92982.17980.01850.01960.02001.69691.91022.159823/4331/4a52.75003.00003.25000.01570.01610.01672.73432.98393.23332.56702.81703.05300.01040.01080.01112.55662.80623.04192.38402.63402.85600.02110.02150.02222.36292.61252.833831/233/4a43.25333.50003.75004.00000.01700.01760.01783.48303.73243.98223.30303.53663.78660.01140.01180.01213.29163.52483.77453.10603.32323.57320.02250.02340.02363.08353.29983.549641/2551/262.8752.752.6252.54.50005.00005.50006.00000.01850.01920.01980.02054.48154.98085.48025.97954.27734.76725.25615.74390.01260.01310.01370.01414.26474.75415.24245.72984.05464.53445.01225.48780.02440.02520.02600.02684.03024.50924.98625.4610a To be dispensed with wherever possible.BS 84:195616 BSI 02-2000Table 5 Nuts Normal classLimits and Tolerances123456789Nominal sizeNumber of threads per inchMajor diameterEffective diameterMinor diameterMin.Max.Tol.Min.Max.Tol.Min.in.in.in.in.in.in.in.in.1/8a3/161/44024200.12500.18750.25000.11330.16600.22380.00430.00520.00580.10900.16080.21800.10200.14740.20300.00900.01330.01700.09300.13410.18605/163/87/161816140.31250.37500.43750.28320.34180.39910.00630.00680.00730.27690.33500.39180.25940.31450.36740.01810.01950.02130.24130.29500.34611/29/16a5/81212110.50000.56250.62500.45430.51710.57520.00770.00800.00840.44660.50910.56680.41690.47940.53380.02370.02370.02520.39320.45570.508611/16a3/47/8111090.68750.75000.87500.63790.69500.81350.00860.00900.00960.62930.68600.80390.59630.64900.76200.02520.02700.02920.57110.62200.7328111/811/48771.00001.12501.25000.93021.04421.16960.01020.01070.01110.92001.03351.15850.87200.97761.10260.03200.03560.03560.84000.94201.067011/213/42654.51.50001.75002.00001.40531.63481.87140.01200.01290.01371.39331.62191.85771.32691.54081.76680.04030.04700.05141.28661.49381.715421/421/223/4443.52.25002.50002.75002.10432.35482.58270.01440.01490.01572.08992.33992.56701.98682.23682.44810.05700.05700.06411.92982.17982.3840331/4a31/53.00003.25003.50002.83313.06973.32010.01610.01670.01712.81703.05303.30302.69812.92453.17450.06410.06850.06852.63402.85603.106033/4a441/2332.8753.75004.00004.50003.55433.80474.29620.01770.01810.01893.53663.78664.27733.39693.64694.13120.07370.07370.07663.32323.57324.0546551/262.752.6252.55.00005.50006.00004.78695.27665.76510.01970.02050.02124.76725.25615.74394.61415.09545.57480.07970.08320.08704.53445.01225.4878a To be dispensed with wherever possible.标准分享网 w w w .b z f x w .c o m 免费下载BS 84:1956 BSI 02-200017Table 6 Bolts Free classLimits and Tolerancesa) Nominal sizes up to and including 3/4 in.1234567891011121314Nominal sizeNumber of threads per inchMajor diameterEffective diameterMinor diameterUnplated or before platingAfter platingUnplated or before platingAfter platingUnplated or before platingAfter platingMax.Tol.Min.Max.Max.Tol.Min.Max.Max.Tol.Min.Max.in.in.in.in.in.in.in.in.in.in.in.in.in.1/8a3/161/44024200.12380.18630.24880.00590.00720.00800.11790.17910.24080.12500.18750.25000.10780.15960.21680.00430.00520.00580.10350.15440.21100.10900.16080.21800.09180.13290.18480.00750.00930.01030.08430.12360.17450.09300.13410.18605/163/87/161816140.31120.37360.43600.00870.00930.01000.30250.36430.42600.31250.37500.43750.27560.33360.39030.00630.00680.00730.26930.32680.38300.27690.33500.39180.24000.29360.34460.01100.01180.01260.22900.28180.33200.24130.29500.34611/29/16a5/81212110.49850.56090.62330.01060.01090.01140.48790.55000.61190.50000.56250.62500.44510.50750.56510.00770.00800.00840.43740.49950.55670.44660.50910.56680.39170.45410.50690.01350.01380.01440.37820.44030.49250.39320.45570.508611/16a3/411100.68580.74820.01160.01220.67420.73600.68750.75000.62760.68420.00860.00900.61900.67520.62930.68600.56940.62020.01460.01530.55480.60490.57110.6220b) Nominal sizes above 3/4 in.1234567891011Nominal sizeNumber of threads per in.Major diameterEffective diameterMinor diameterMax.Tol.Min.Max.Tol.Min.Max.Tol.Min.in.in.in.in.in.in.in.in.in.in.7/8111/89870.87501.00001.12500.01290.01370.01450.86210.98631.11050.80390.92001.03350.00960.01020.01070.79430.90981.02280.73280.84000.94200.01630.01730.01830.71650.82270.923711/411/213/47651.25001.50001.75000.01490.01610.01741.23511.48391.73261.15851.39331.62190.01110.01200.01291.14741.38131.60901.06701.28661.49380.01870.02020.02181.04831.26641.4720221/421/24.5442.00002.25002.50000.01840.01940.01991.98162.23062.48011.85772.08992.33990.01370.01440.01491.84402.07552.32501.71541.92982.17980.02310.02440.02491.69231.90542.154923/4331/4a52.75003.00003.25000.02100.02140.02232.72902.97863.22772.56702.81703.05300.01570.01610.01672.55132.80093.03632.38402.63402.85600.02640.02680.02782.35762.60722.828231/233/4a43.25333.50003.75004.00000.02270.02350.02393.47733.72653.97613.30303.53663.78660.01710.01770.01813.28593.51893.76853.10603.32323.57320.02820.02930.02963.07783.29393.543641/2551/262.8752.752.6252.54.50005.00005.50006.00000.02480.02570.02670.02754.47524.97435.47335.97254.27734.76725.25615.74390.01890.01970.02050.02124.25844.74755.23565.72274.05464.53445.01225.48780.03070.03180.03280.03394.02394.50264.97945.4539a To be dispensed with wherever possible.BS 84:195618 BSI 02-2000Fine thread series, B.S.F.Table 7 Basic sizes12345678Nominal sizeNumber of threads per inchPitchDepth of threadMajor diameterEffective diameterMinor diameterCross sectional area at bottom of threadin.in.in.in.in.in.sq. in.3/16ab7/32a1/43228260.031250.035710.038460.02000.02290.02460.18750.21880.25000.16750.19590.22540.14750.17300.20080.01710.02350.03179/32a5/163/82622200.038460.045450.050000.02460.02910.03200.28120.31250.37500.25660.28340.34300.23200.25430.31100.04230.05080.07607/161/29/161816160.055560.062500.062500.03560.04000.04000.43750.50000.56250.40190.46000.52250.36630.42000.48250.10540.13850.18285/811/16a3/41414120.071430.071430.083330.04570.04570.05340.62500.68750.75000.57930.64180.69660.53360.59610.64320.22360.27910.32497/8111100.090910.100000.05820.06400.87501.00000.81680.93600.75860.87200.45200.597211/811/413/8a9980.111110.111110.125000.07110.07110.08001.12501.25001.37501.05391.17891.29500.98281.10781.21500.75860.96391.159011/215/8a13/48870.125000.125000.142860.08000.08000.09151.50001.62501.75001.42001.54501.65851.34001.46501.56701.41001.68601.9280221/421/27660.142860.166670.166670.09150.10670.10672.00002.25002.50001.90852.14332.39331.81702.03662.28662.59303.25804.106023/4331/46550.166670.200000.200000.10670.12810.12812.75003.00003.25002.64332.87193.12192.53662.74582.99385.05405.91307.039031/233/4441/40.222220.222220.222220.250000.14230.14230.14230.16013.50003.75004.00004.25003.35773.60773.85774.08993.21543.46543.71543.92988.12009.432010.840012.1300NOTEIt is recommended that for larger diameters in this series four threads per inch be used.a To be dispensed with wherever possible.b The use of 2 B.A. threads is recommended in place of 3/16 in. B.S.F.标准分享网 w w w .b z f x w .c o m 免费下载BS 84:1956 BSI 02-200019Table 8 Bolts Close classLimits and Tolerances1234567891011Nominal sizeNumber of threads per in.Major diameterEffective diameterMinor diameterMax.Tol.Min.Max.Tol.Min.Max.Tol.Min.in.in.in.in.in.in.in.in.in.in.3/16ab7/32a1/43228260.18750.21880.25000.00400.00430.00450.18350.21450.24550.16750.19590.22540.00220.00240.00250.16530.19350.22290.14750.17300.20080.00450.00490.00500.14300.16810.19589/32a5/163/82622200.28120.31250.37500.00460.00480.00510.27660.30770.36990.25660.28340.34300.00260.00270.00290.25400.28070.34010.23200.25430.31100.00510.00550.00580.22690.24880.30527/161/29/161816160.43750.50000.56250.00550.00580.00590.43200.49420.55660.40190.46000.52250.00310.00330.00340.39880.45670.51910.36630.42000.48250.00620.00650.00660.36010.41350.47595/811/16a3/41414120.62500.68750.75000.00630.00640.00680.61870.68110.74320.57930.64180.69660.00360.00370.00390.57570.63810.69270.53360.59610.64320.00710.00720.00770.52650.58890.63557/8111100.87501.00000.00720.00760.86780.99240.81680.93600.00420.00440.81260.93160.75860.87200.00810.00850.75050.863511/811/413/8a9981.12501.25001.37500.00790.00810.00851.11711.24191.36651.05391.17891.29500.00460.00480.00501.04931.17411.29000.98281.10781.21500.00890.00910.00960.97391.09871.205411/215/8a13/48871.50001.62501.75000.00870.00880.00931.49131.61621.74071.42001.54501.65850.00520.00530.00551.41481.53971.65301.34001.46501.56700.00980.00990.01041.33021.45511.5566221/421/223/43766652.00002.25002.50002.75003.00000.00950.01020.01040.01060.01131.99052.23982.48962.73942.98871.90852.14332.39332.64332.87190.00580.00610.00630.00650.00691.90272.13722.38702.63682.86501.81702.03662.28662.53662.74380.01070.01140.01160.01190.01271.80632.02522.27502.52472.7311a To be dispensed with wherever possible.b The use of 2 B.A. threads is recommended in place of 3/16 in. B.S.F.BS 84:195620 BSI 02-2000Table 9 Nuts Medium classLimits and Tolerances123456789Nominal sizeNumber of threads per inchMajor diameterEffective diameterMinor diameterMin.Max.Tol.Min.Max.Tol.Min.in.in.in.in.in.in.in.in.3/16ab7/32a1/43228260.18750.21880.25000.17080.19950.22910.00330.00360.00370.16750.19590.22540.15770.18410.21250.01020.01110.01170.14750.17300.20089/32a5/163/82622200.28120.31250.37500.26050.28750.34740.00390.00410.00440.25660.28340.34300.24370.26840.32800.01170.01410.01700.23200.25430.31107/161/29/161816160.43750.50000.56250.40660.46500.52770.00470.00500.00520.40190.46000.52250.38440.43950.50200.01810.01950.01950.36630.42000.48255/811/16a3/41414120.62500.68750.75000.58470.64740.70250.00540.00560.00590.57930.64180.69660.55490.61740.66690.02130.02130.02370.53360.59610.64327/8111/811/413/8a11109980.87501.00001.12501.25001.37500.82300.94261.06081.18611.30250.00620.00660.00690.00720.00750.81680.93601.05391.17891.29500.78380.89901.01201.13701.24700.02520.02700.02920.02920.03200.75860.87200.98281.10781.215011/215/8a13/48871.50001.62501.75001.42771.55291.66680.00770.00790.00831.42001.54501.65851.37201.49701.60260.03200.03200.03561.34001.46501.5670221/421/27662.00002.25002.50001.91722.15252.40280.00870.00920.00951.90852.14332.39331.85262.07692.32690.03560.04030.04031.81702.03662.286623/43652.75003.00002.65312.88220.00980.01032.64332.87192.57692.79080.04030.04702.53662.7438a To be dispensed with wherever possible.b The use of 2 B.A. threads is recommended in place of 3/16 in. B.S.F.标准分享网 w w w .b z f x w .c o m 免费下载BS 84:1956 BSI 02-200021Table 10 Bolts Medium classLimits and Tolerancesa) Nominal sizes up to and including 3/4 in.1234567891011121314Nominal sizeNumber of threads per inchMajor diameterEffective diameterMinor diameterUnplated or before platingAfter platingUnplated or before platingAfter platingUnplated or before platingAfter platingMax.Tol.Min.Max.Max.Tol.Min.Max.Max.Tol.Min.Max.in.in.in.in.in.in.in.in.in.in.in.in.in.3/16ab7/32a1/43228260.18640.21770.24890.00510.00550.00570.18130.21220.24320.18750.21880.25000.16640.19480.22430.00330.00360.00370.16310.19120.22060.16750.19590.22540.14640.17190.19970.00680.00740.00760.13960.16450.19210.14750.17300.20089/32a5/163/82622200.28000.31130.37370.00590.00620.00660.27410.30510.36710.28120.31250.37500.25540.28220.34170.00390.00410.00440.25150.27810.33730.25660.28340.34300.23080.25310.30970.00780.00840.00890.22300.24470.30080.23200.25430.31107/161/29/161816160.43610.49850.56100.00710.00750.00770.42900.49100.55330.43750.50000.56250.40050.45850.52100.00470.00500.00520.39580.45350.51580.40190.46000.52250.36490.41850.48100.00940.01000.01020.35550.40850.47080.36630.42000.48255/811/16a3/41414120.62340.68580.74820.00810.00830.00880.61530.67750.73940.62500.68750.75000.57770.64010.69480.00540.00560.00590.57230.63450.68890.57930.64180.69660.53200.59440.64140.01070.01090.01170.52130.58350.62970.53360.59610.6432b) Nominal sizes above 3/4 in.1234567891011Nominal sizeNumber of threads per in.Major diameterEffective diameterMinor diameterMax.Tol.Min.Max.Tol.Min.Max.Tol.Min.in.in.in.in.in.in.in.in.in.in.7/8111/8111090.87501.00001.12500.00920.00980.01020.86580.99021.11480.81680.93601.05390.00620.00660.00690.81060.92941.04700.75860.87200.98280.01220.01290.01360.74640.85910.969211/413/8a11/29881.25001.37501.50000.01050.01100.01121.23951.36401.48881.17891.29501.42000.00720.00750.00771.17171.28751.41231.10781.21501.34000.01390.01460.01481.09391.20041.325215/8a13/428771.62501.75002.00000.01150.01200.01241.61351.73801.98761.54501.65851.90850.00790.00830.00871.53711.65021.89981.46501.56701.81700.01500.01580.01621.45001.55121.800821/421/223/4366652.25002.50002.75003.00000.01320.01360.01390.01482.23682.48642.73612.98522.14332.39332.64332.87190.00920.00950.00980.01032.13412.38382.63352.86162.03662.28662.53662.74380.01730.01770.01800.01932.01932.26892.51862.7245a To be dispensed with wherever possible.b The use of 2 B.A. threads is recommended in place of 3/16 in. B.S.F.BS 84:195622 BSI 02-2000Table 11 Nuts Normal classLimits and Tolerances123456789Nominal sizeNumber of threads per inchMajor diameterEffective diameterMinor diameterMin.Max.Tol.Min.Max.Tol.Min.in.in.in.in.in.in.in.in.3/16ab7/32a1/43228260.18750.21880.25000.17250.20120.23100.00500.00530.00560.16750.19590.22540.15770.18410.21250.01020.01110.01170.14750.17300.20089/32a5/163/82622200.28120.31250.37500.26240.28960.34960.00580.00620.00660.25660.28340.34300.24370.26840.32800.01170.01410.01700.23200.25430.31107/161/29/161816160.43750.50000.56250.40890.46740.53020.00700.00740.00770.40190.46000.52250.38440.43950.50200.01810.01950.01950.36630.42000.48255/811/16a3/41414120.62500.68750.75000.58740.65020.70540.00810.00840.00880.57930.64180.69660.55490.61740.66690.02130.02130.02370.53360.59610.64327/8111100.87501.00000.82610.94590.00930.00990.81680.93600.78380.89900.02520.02700.75860.872011/811/413/8a9981.12501.25001.37501.06431.18971.30630.01040.01080.01131.05391.17891.29501.01201.13701.24700.02920.02920.03200.98281.10781.215011/215/8a13/48871.50001.62501.75001.43161.55691.67090.01160.01190.01241.42001.54501.65851.37201.49701.60260.03200.03200.03561.34001.46501.5670221/421/27662.00002.25002.50001.92152.15702.40750.01300.01370.01421.90852.14332.39331.85262.07692.32690.03560.04030.04031.81702.03662.286623/43652.75003.00002.65802.88740.01470.01552.64332.87192.57692.79080.04030.04702.53662.7438a To be dispensed with wherever possible.b The use of 2 B.A. threads is recommended in place of 3/16 in. B.S.F.标准分享网 w w w .b z f x w .c o m 免费下载BS 84:1956 BSI 02-200023Table 12 Bolts Free classIntroductory notes to Table 13 Selected thread series Fractional sizes1 Preferred diametersIt is strongly recommended that the preferred diameters should be used and, whenever the design permits, a “1st choice” diameter be selected.In an extreme case, when even the “2nd choice” diameters cannot be utilized, a suitable “3rd choice” diameter should be selected as follows:a) Up to 11/2in.: the nearest 1/32in. size.b) Above 11/2in. and up to 6 in.: the nearest 1/16in. size.c) Above 6 in.: the nearest 1/8in. size.Limits and Tolerancesa) Nominal sizes up to and including 3/4 in.1234567891011121314Nominal sizeNumber of threads per inchMajor diameterEffective diameterMinor diameterUnplated or before platingAfter platingUnplated or before platingAfter platingUnplated or before platingAfter platingMax.Tol.Min.Max.Max.Tol.Min.Max.Max.Tol.Min.Max.in.in.in.in.in.in.in.in.in.in.in.in.in.3/16ab7/32a1/43228260.18640.21770.24890.00680.00720.00760.17960.21050.24130.18750.21880.25000.16640.19480.22430.00500.00530.00560.16140.18950.21870.16750.19590.22540.14640.17190.19970.00850.00910.00950.13790.16280.19020.14750.17300.20089/32a5/163/82622200.28000.31130.37370.00780.00830.00880.27220.30300.36490.28120.31250.37500.25540.28220.34170.00580.00620.00660.24960.27600.33510.25660.28340.34300.23080.25310.30970.00970.01050.01110.22110.24260.29860.23200.25430.31107/161/29/161816160.43610.49850.56100.00940.00990.01020.42670.48860.55080.43750.50000.56250.40050.45850.52100.00700.00740.00770.39350.45110.51330.40190.46000.52250.36490.41850.48100.01170.01240.01270.35320.40610.46830.36630.42000.48255/811/16a3/41414120.62340.68580.74820.01080.01110.01170.61260.67470.73650.62500.68750.75000.57770.64010.69480.00810.00840.00880.56960.63170.68600.57930.64180.69660.53200.59440.64140.01340.01370.01460.51860.58070.62680.53360.59610.6432b) Nominal sizes above 3/4 in.1234567891011Nominal sizeNumber of threads per in.Major diameterEffective diameterMinor diameterMax.Tol.Min.Max.Tol.Min.Max.Tol.Min.in.in.in.in.in.in.in.in.in.in.7/8111/8111090.87501.00001.12500.01230.01310.01370.86270.98691.11130.81680.93601.05390.00930.00990.01040.80750.92611.04350.75860.87200.98280.01530.01620.01710.74330.85580.965711/413/8a11/29881.25001.37501.50000.01410.01480.01511.23591.36021.48491.17891.29501.42000.01080.01130.01161.16811.28371.40841.10781.21501.34000.01750.01840.01871.09031.19661.321315/8a13/428771.62501.75002.00000.01550.01620.01681.60951.73381.98321.54501.65851.90850.01190.01240.01301.53311.64611.89551.46501.56701.81700.01900.02000.02051.44601.54701.796521/421/223/4366652.25002.50002.75003.00000.01780.01830.01880.01992.23222.48172.73122.98012.14332.39332.64332.87190.01370.01420.01470.01552.12962.37912.62862.85642.03662.28662.53662.74380.02190.02240.02290.02442.01472.26422.51372.7194a To be dispensed with wherever possible.b The use of 2 B.A. threads is recommended in place of 3/16 in. B.S.F.BS 84:195624 BSI 02-2000Before selecting a “3rd choice” diameter, care should be taken to ascertain whether a “1st choice” or “2nd choice” in the alternative table of the decimal series could not be used instead.2 Preferred pitchesThe coarsest pitch suitable to the design should normally be used. Those pitches in brackets are included to meet less usual design requirements, and their general use should be avoided. However, in some specialized branches of design, particular pitches may be very commonly required and it may then be desirable to treat those most commonly required as “1st choice” pitches irrespective of the preference indicated above.3 Extra fine pitchesThese recommendations do not apply to extra fine pitches such as occur on thin-walled designs.Selected thread series, Whit. STable 13 Preferred diameters and pitches Fractional sizes123456789101112Preferred basic major diametersStandard pitches (t.p.i.)Preferred pitches (t.p.i.)1st choice2nd choiceB.S.W. seriesB.S.F. series4681216202632in.in.1/45/163/820181626222026263232327/161/29/1614121218161620202626265/83/411/1611111014141216162020202626267/813/1615/16912111216(16)(16)20202026(26)(26)111/811/1687109121212(16)(16)(16)202020(26)(26)(26)11/413/1615/1679(6)(8)(8)121212(16)(16)(16)202020(26)(26)(26)13/817/168(6)(6)(8)1212(16)(16)2020(26)(26)标准分享网 w w w .b z f x w .c o m 免费下载BS 84:1956 BSI 02-200025Table 13 Preferred diameters and pitches Fractional sizes123456789101112Preferred basic major diametersStandard pitches (t.p.i.)Preferred pitches (t.p.i.)1st choice2nd choiceB.S.W. seriesB.S.F. series4681216202632in.in.11/213/415/865887(6)121212(16)1616202020(26)(26)(26)217/821/841/27(6)(6)(8)81212121616162020(20)(26)(26)21/421/223/84466(6)888121212161616(20)(20)(20)23/425/827/831/26(6)(6)888121212161616(20)(20)(20)331/431/831/231/455(6)(6)(6)88812(12)(12)161616(20)31/233/835/831/441/2(6)(6)(6)888(12)(12)(12)16161633/4437/83341/241/2(6)(6)(6)888(12)(12)(12)161616BS 84:195626 BSI 02-2000Table 13 Preferred diameters and pitches Fractional sizesIntroductory notes to Table 13A Selected thread series Decimal sizes1 Preferred diametersIt is strongly recommended that the preferred diameters should be used and that, whenever the design permits, a “1st choice” diameter be selected.In an extreme case, when even the “2nd choice” diameters cannot be utilized, a suitable “3rd choice” diameter should be selected as follows:a) From 1.5 in. to 6 in.: select from the non-preferred 0.1 in. sizes, such as 2.2, 2.3, 2.7 and 2.8. Should these prove unsuitable, choose the nearest 0.05 in. diameter.b) From 6 in. to 20 in.: select from the four 0.1 in. sizes similar to those shown in the table for the “2nd choice” below 6 in. Only as a last resort should the non-preferred 0.1 in. sizes such as 6.2, 6.3, 6.7 and 6.8 be used.Before selecting a “3rd choice” diameter, care should be taken to ascertain whether a “1st choice” or “2nd choice” in the alternative table of the fractional series could not be used instead.2 Preferred pitchesThe coarsest pitch suitable to the design should normally be used. Those pitches in brackets are included to meet less usual design requirements and their general use should be avoided. However, in some specialized branches of design, particular pitches may be very commonly required, and it may then be desirable to treat those most commonly required as “1st choice” pitches irrespective of the preference indicated above.123456789101112Preferred basic major diametersStandard pitches (t.p.i.)Preferred pitches (t.p.i.)1st choice2nd choiceB.S.W. seriesB.S.F. series4681216202632in.in.41/441/843/844(6)(6)(6)888(12)(12)(12)16161641/243/445/827/8444(6)(6)(6)888(12)(12)(12)161616547/851/823/4444(6)(6)(6)888(12)(12)(12)16161651/451/253/825/8444(6)(6)(6)888(12)(12)(12)16161653/455/857/8444(6)(6)(6)888(12)(12)(12)161616661/261/421/2444(6)(6)(6)888(12)(12)(12)161616763/444(6)688(12)121616NOTELarger diameters have the same preferred diameter steps and the same preferred pitches as for the range 6.0 to 7.0 inches.标准分享网 w w w .b z f x w .c o m 免费下载BS 84:1956 BSI 02-2000273 Extra fine pitchesThese recommendations do not apply to extra fine pitches such as occur on thin-walled designs.Table 13A Preferred diameters and pitches Decimal sizes123456789101112Preferred basic major diametersStandard pitches (t.p.i.)Preferred pitches (t.p.i.)1st choice2nd choiceB.S.W. seriesB.S.F. series4681216202632in.in.68(6)(6)(8)(8)121212(16)(16)16202010(26)(26)(26)1.752.01.9541/277(6)(8)121212161616202020(26)(26)(26)46(6)(6)888121212161616(20)(20)(20)2.52.752.6431/266(6)888121212161616(20)(20)(20)3.02.93.131/25(6)(6)(6)8881212(12)161616(20)(20)31/431/4541/2(6)(6)(6)888(12)(12)(12)1616163.753.63.9341/2(6)(6)(6)888(12)(12)(12)161616BS 84:195628 BSI 02-2000Table 13A Preferred diameters and pitches Decimal sizes123456789101112Preferred basic major diametersStandard pitches (t.p.i.)Preferred pitches (t.p.i.)1st choice2nd choiceB.S.W. seriesB.S.F. series4681216202632in.in.4.04.254.1341/24(6)(6)(6)888(12)(12)(12)161627/8444(6)(6)(6)888(12)(12)(12)1616164.755.04.923/4444(6)(6)(6)888(12)(12)(12)1616444(6)(6)(6)888(12)(12)(12)1616165.55.755.625/8444(6)(6)(6)888(12)(12)(12)1616166.05.96.2521/2444(6)(6)(6)888(12)(12)(12)1616166.57.06.75444(6)(6)6888(12)(12)12161616NOTELarger diameters have the same preferred diameter steps and the same preferred pitches as for the range 6.0 to 7.0 inches.标准分享网 w w w .b z f x w .c o m 免费下载BS 84:1956 BSI 02-200029Table 14 Depths of thread for various pitchesWhitworth form special threadsExamples illustrating the use of Table 14 to Table 20Basic and design sizes for bolt and nut:1234Number of threads per inchaPitchBasic depth of threadsTwice basic depth of threadin.in.in.4036320.025000.027780.031250.01600.01780.02000.03200.03560.04002826240.035710.038460.041670.02290.02460.02670.04580.04920.05342018160.050000.055560.062500.03200.03560.04000.06400.07120.0800141211100.071430.083330.090910.100000.04570.05340.05820.06400.09140.10680.11640.12808640.125000.166670.250000.08000.10670.16010.16000.21340.3202NOTEBasic effective diameter = basic major diameter basic depth of thread (Col. 3).Basic minor diameter = basic major diameter twice basic depth of thread (Col. 4).a The numbers of t.p.i. in heavy type are to be preferred.Example 1. Bolt 1.25 in. 12 Whit. S. (close)Nut 1.25 in. 12 Whit. S. (medium)Major dia.1.2500 in.Effective dia.1.2500 0.0534 = 1.1966 in.Table 14Minor dia.1.2500 0.1068 = 1.1432 in.Table 14Tolerances for bolt (close class):Effective dia. 0.0042 in.Table 16Major dia. (0.0042 + 0.0029) = 0.0071 in. Table 16Minor dia. (0.0042 + 0.0038) = 0.0080 in. Table 16Tolerances for nut (medium class):Effective dia.+ 0.0062 in.Table 17Minor dia.+ 0.0237 in.Table 17BS 84:195630 BSI 02-2000Limits:Bolt. Major dia.1.2500 to 1.2429 in.Effective dia. 1.1966 to 1.1924 in.Minor dia.1.1432 to 1.1352 in.Nut. Major dia.Not less than 1.2500 in.Effective dia. 1.1966 to 1.2028 in.Minor dia.1.1432 to 1.1669 in.Example 2. Bolt 0.5 in. 20 Whit. S. (free)Nut0.5 in. 20 Whit. S. (normal)Basic sizes for bolt and nut and design sizes for nut:Major dia.0.5000 in.Effective dia. 0.5000 0.0320 = 0.4680 in.Table 14Minor dia.0.5000 0.0640 = 0.4360 in.Table 14Design sizes for bolt:Major dia.Basic size Allowance = 0.5000 0.0014 = 0.4986 in.Table 15Effective dia. Basic size Allowance = 0.4680 0.0014 = 0.4666 in.Table 15Minor dia.Basic size Allowance = 0.4360 0.0014 = 0.4346 in.Table 15Tolerances for bolt (free class):Effective dia. 0.0068Table 20Major dia. (0.0068 + 0.0022) = 0.0090 in.Table 20Minor dia. (0.0068 + 0.0045) = 0.0113 in.Table 20Tolerances for nut (normal class):Effective dia. + 0.0068 in.Table 19Minor dia.+ 0.0170 in.Table 19Limits:Bolt. Major dia.0.4986 to 0.4896 in.Effective dia. 0.4666 to 0.4598 in.Minor dia.0.4346 to 0.4233 in.Nut. Major dia.Not less than 0.5000 in.Effective dia. 0.4680 to 0.4748 in.Minor dia.0.4360 to 0.4530 in.标准分享网 w w w .b z f x w .c o m 免费下载BS 84:1956 BSI 02-200031Table 15 Bolts Medium and free class allowancesTable 16 Bolts Close classDiameters in inchesUnit of allowance = 0.001 in.Number of threads per in.aAllowance on major, effective and minor diametersBasic major diameterabove1/81/41/2up to and including1/41/23/440, 3632, 2826, 2018, 1614, 1.61.8a The numbers of t.p.i. in heavy type are to be preferred.TolerancesDiameters in inchesUnit of tolerance = 0.001 in.Number of threads per in.aTolerance on effective diameterTolerance on major diameterTolerance on minor diameterBasic major diameterabove1/81/41/23/411/4234681115Add the following to the “tolerance on effective diameter”up to and including1/41/23/411/42346811152040, 3632, 2826, 3.03.33.6 2.02018, 1614, 123.04.03.64.03.23.811, 105.05.56.0 4.14.6645.6 5.36.5a The numbers of t.p.i. in heavy type are to be preferred. BS 84:195632 BSI 02-2000Table 17 Nuts Medium classTable 18 Bolts Medium classTolerancesDiameters in inchesUnit of tolerance = 0.001 in.Number of threads per in.aTolerance on effective diameterTolerance on minor diameterBasic major diameterabove1/81/41/23/411/4234681115Total toleranceup to and including1/41/23/411/42346811152040, 3632, 2826, 4.04.65.04.95.011.113.32018, 1614, 5.36.05.56.07.07.717.019.523.711, 1088.29.09.410.2 10.727.032.040.3410.0 10.3 10.7 11.1 11.5 11.9 12.4 57.0a The numbers of t.p.i. in heavy type are to be preferred.TolerancesDiameters in inchesUnit of tolerance = 0.001 in.Number of threads per in.aTolerance on effective diameterTolerance on major diameterTolerance on minor diameterBasic major diameterabove1/81/41/23/411/4234681115Add the following to the “tolerance on effective diameter”up to and including1/41/23/411/42346811152040, 3632, 2826, 4.04.65.04.95.01.92.02018, 1614, 5.36.05.56.07.05.811, 106.37.1648.48.710.09.010.39.410.79.810.711.9 8.210.0a The numbers of t.p.i. in heavy type are to be preferred. 标准分享网 w w w .b z f x w .c o m 免费下载BS 84:1956 BSI 02-200033Table 19 Nuts Normal classTable 20 Bolts Free classTolerancesDiameters in inchesUnit of tolerance = 0.001 in.Number of threads per in.aTolerance on effective diameterTolerance on minor diameterBasic major diameterabove1/81/41/23/411/4234681115Total toleranceup to and including1/41/23/411/42346811152040, 3632, 2826, 6.07.58.08.69.611.113.32018, 1614, 8.010.410.010.910.611.517.019.523.711, 1089.610.711.812.812.313.4 14.027.032.06412.5 13.114.913.615.414.116.014.816.615.4 18.740.357.0a The numbers of t.p.i. in heavy type are to be preferred.TolerancesDiameters in inchesUnit of tolerance = 0.001 in.Number of threads per in.aTolerance on effective diameterTolerance on major diameterTolerance on minor diameterBasic major diameterabove1/81/41/23/411/4234681115Add the following to the “tolerance on effective diameter”up to and including1/41/23/411/42346811152026, 246.2 6.7 8.62.04.12018, 1614, 8.010.410.010.910.65.811, 1089.610.711.812.812.313.4 14.07.16412.5 13.114.913.615.414.116.014.816.615.4 8.210.0a The numbers of t.p.i. in heavy type are to be preferred. BS 84:195634 BSI 02-2000Appendix A Truncated Whitworth form threads with flat crestsTruncated Whitworth threads are only to be supplied when specially ordered or by arrangement with the purchaser.Form of truncated Whitworth thread. In the truncated Whitworth form of thread the basic rounded crests at the major diameter of the bolt and the minor diameter of the nut are removed at their junctions with the straight flanks of the basic thread form (see Figure 7). The resulting flat crests of the threads are given suitable manufacturing tolerances, which are negative on the bolt and positive on the nut.NOTEIn the case of nuts of standard Whitworth form, by virtue of the generous tolerance allowed on the minor diameter of the nut, the form of the crest of the thread at the minor diameter of the nut may vary between the basic rounding at the minimum diameter and a flat at the maximum diameter. For a nut with a truncated thread made in accordance with the present Appendix, the crest of the thread at the minor diameter will always be flat, the minimum minor diameter corresponding with the point of tangency of the radius of the normal Whitworth form thread and the maximum minor diameter to that laid down for ordinary Whitworth form threads.Tolerances. For truncated threads, the limits and tolerances are the same as for threads of standard Whitworth form, with the exception of the major diameters of the bolts and the minor diameters of the nuts.Tolerances on major diameter of bolt and minor diameter of nut. Figure 7 shows the upper and lower limiting outlines of a close class bolt and medium class nut with truncated threads. In the case of the bolt, the design size of the major diameter is reduced by an amount U equal to double the depth of the normal rounded crest, which is equal to 0.147835p. U is twice the distance, measured normal to the axis, from the intersection of the radius r with the flank of the thread to the basic major diameter. This is shown in Figure 7. In the case of the nut, the design size of the minor diameter is increased by the same amount.The tolerances on the flat crests at the major diameter of the bolt and on the flat crests at the minor diameter of the nut are denoted by A and B respectively. For any one pitch these tolerances remain unchanged for all recommended combinations of classes of bolts and nuts.The following formulae are used for determining A and B:In the case of the nut, the upper limit of tolerance for the flat crests at the minor diameter is made the same as that for threads of standard Whitworth form, so that:The values of U, A and B are given in Table 21.Table 22 and Table 23 give the maximum and minimum values of the major diameters of bolts and minor diameters of nuts for B.S.W. and B.S.F. truncated threads.Designation of truncated Whitworth form threads. Truncated Whitworth form threads shall be designated as laid down on page 4 for normal Whitworth form threads with the addition of the abbreviation “trunc.”.Gauging system for truncated Whitworth form threads. The following limit-gauging system is recommended for controlling truncated Whitworth form threads:For bolt:i) GO screw ring or calliper gauge.ii) NOT GO effective diameter calliper gauge.iii) GO plain calliper gauge for flat crests.iv) NOT GO plain calliper gauge for flat crests.U + A = 0.2 p + 0.003 in.A is the difference between the rounded-off values of (U + A) and U.U + B = 0.2 p + 0.004 in. for 26 t.p.i. and finer0.2 p + 0.005 in. for 24 and 22 t.p.i.0.2 p + 0.007 in. for 20 t.p.i. and coarserB is the difference between the rounded-off values of (U + B) and U.标准分享网 w w w .b z f x w .c o m 免费下载BS 84:1956 BSI 02-200035For nut:i) GO screw plug gauge.ii) NOT GO effective diameter plug gauge.iii) GO plain plug gauge for flat crests.iv) NOT GO plain plug gauge for flat crests.If it is desired to ensure assembly between parts, both of which have truncated threads, the two GO screw gauges i) could also have truncated threads. The roots of the threads of these gauges should not be cleared however, but should conform to the normal Whitworth form threads at the roots, in order to control possible eccentricity between the flat crests of the truncated threads on the parts and their effective diameters. On the other hand, if it is desired to ensure assembly between parts made by one manufacturer with truncated threads and parts made by another manufacturer which may have normal Whitworth form threads, the two GO screw gauges for the truncated threads must have normal rounded crests as well as normal rounded roots.As a general practice, therefore, it is recommended that the two GO screw gauges for truncated threads should have normal (full form) Whitworth threads. The threads of the two NOT GO effective diameter gauges should, as usual, be cleared at the crests and roots, as recommended in BS 919, “Screw thread gauge tolerances”.The GO plain calliper gauge and the GO plain plug gauge referred to in iii) above are not strictly essential, if the GO screw gauges have normal rounded roots, as recommended above. In the event of the work refusing to pass the GO screw gauges, however, these plain GO gauges for the crests of the thread could be usefully employed to determine whether or not the flat crest diameter of the bolt was dimensionally too large, or the flat minor diameter of the nut too small.BS 84:195636 BSI 02-2000Figure 7 Tolerance zones for truncated Whitworth thread 1/4 in. B.S.W. (20 t.p.i.) illustrated Close class bolt and medium class nut.标准分享网 w w w .b z f x w .c o m 免费下载BS 84:1956 BSI 02-200037Table 21 Basic dataUnit = 0.001 inch12345Number of threads per inchBolt major diameterNut minor diameterNominal truncationTolerance on truncated major diameterNominal truncationTolerance on truncated minor diameterUaAaUaBa4036328264.85.07.1222018169.910.310.712111012.313.48.212.313.414.811.411.812.298716.418.510.516.418.521.112.813.514.5654.524.629.632.911.713.414.524.629.632.915.717.418.543.537.042.216.017.937.042.220.021.93.2532.87545.549.351.419.020.421.245.549.351.423.024.425.22.752.6252.553.856.359.121.922.923.953.856.359.125.926.927.9NOTE 1To obtain the upper limit for the major diameter of the truncated thread of a close class bolt, subtract the value in Col. 2 from its basic major diameter. To obtain the upper limit for the major diameter of the truncated thread of a medium or free class bolt subtract the sum of the appropriate allowance, if any, and the value in Col. 2 from its basic major diameter. To obtain the lower limit for the minor diameter of the truncated thread of a nut, add the value in Col. 4 to its basic minor diameter.NOTE 2The tolerances on bolts are negative and those on nuts positive.NOTE 3For any one pitch the tolerances for all classes of bolts are the same and for all classes of nuts are the same.a See Figure 7.BS 84:195638 BSI 02-2000Truncated coarse thread series, B.S.WTable 22 Bolts and nuts all classesLimits and Tolerances1234567891011Nominal sizeNumber of threads per in.Bolt major diameter close classBolt major diameter medium and free classesNut minor diameter all classesMax.Tol.Min.Max.Tol.Min.Max.Tol.Min.in.in.in.in.in.in.in.in.in.in.1/8a3/161/44024200.12130.18130.24260.00430.00510.00560.11700.17620.23700.12010.18010.24140.00430.00510.00560.11580.17500.23580.10200.14740.20300.00530.00710.00960.09670.14030.19345/163/87/161816140.30430.36580.42690.00590.00630.00670.29840.35950.42020.30300.36440.42540.00590.00630.00670.29710.35810.41870.25940.31450.36740.00990.01030.01070.24950.30420.35671/29/16a5/81212110.48770.55020.61160.00740.00740.00780.48030.54280.60380.48620.54860.60990.00740.00740.00780.47880.54120.60210.41690.47940.53380.01140.01140.01180.40550.46800.522011/16a3/47/8111090.67410.73520.85860.00780.00820.00880.66630.72700.84980.67240.73340.00780.00820.66460.72520.59630.64900.76200.01180.01220.01280.58450.63680.7492111/811/48770.98151.10391.22890.00950.01050.01050.97201.09341.21840.87200.97761.10260.01350.01450.01450.85850.96311.088111/213/42654.51.47541.72041.96710.01170.01340.01451.46371.70701.95261.32691.54081.76680.01570.01740.01851.31121.52341.748321/421/223/4443.52.21302.46302.70780.01600.01600.01792.19702.44702.6899The Limits and Tolerances for Nominal Sizes above 3/4 in. are the same as those of the corresponding size of Close Class bolt1.98682.23682.44810.02000.02000.02191.96682.21682.4262331/4a31/52.95783.20453.45450.01790.01900.01902.93993.18553.43552.69812.92453.17450.02190.02300.02302.67622.90153.151533/4a441/2332.8753.70073.95074.44860.02040.02040.02123.68033.93034.42743.39693.64694.13120.02440.02440.02523.37253.62254.1060551/262.752.6252.54.94625.44375.94090.02190.02290.02394.92435.42085.91704.61415.09545.57480.02590.02690.02794.58825.06855.5469a To be dispensed with wherever possible.标准分享网 w w w .b z f x w .c o m 免费下载BS 84:1956 BSI 02-200039Table 23 Bolts and nuts all classesAppendix B Bases of tolerances and allowances for Whitworth form screw threadsIn deciding upon suitable bases for calculating tolerances and allowances for Whitworth form screw threads, the aim has been to provide a minimum number of simple formulae which would be applicable to the several classes and to all reasonable combinations of diameter and pitch. The formulae adopted give tolerances sufficiently large for the usual methods of screw thread manufacture but not so large that the satisfactory functioning of the screw threads is impaired.Classes of tolerance. The relative magnitudes and dispositions of the effective diameter tolerance zones for the close, medium and free classes of bolts and the medium and normal classes of nuts are shown in Figure 2.The close class bolt and nut effective diameter tolerances are two-thirds of the corresponding values of the medium class bolt and nut tolerances respectively.The free class bolt and normal class nut effective diameter tolerances are one and a half times the corresponding values of the medium class tolerances.Allowances. The free class and medium class bolts of nominal sizes 3/4in. down to 1/4in. have an allowance equal to 30 per cent of the medium class bolt effective diameter tolerance. The allowance for nominal sizes less than 1/4in. is the same as that for 1/4in.The close class bolt has no allowance.Limits and Tolerances1234567891011Nominal sizeNumber of threads per in.Bolt major diameter close classBolt major diameter medium and free classesNut minor diameter all classesMax.Tol.Min.Max.Tol.Min.Max.Tol.Min.in.in.in.in.in.in.in.in.in.in.3/16a7/32a1/43228260.18290.21350.24430.00460.00480.00500.17830.20870.23930.18180.21240.24320.00460.00480.00500.17720.20760.23820.15770.18410.21250.00560.00580.00600.15210.17830.20659/32a5/163/82622200.27550.30580.36760.00500.00540.00560.27050.30040.36200.27430.30460.36630.00500.00540.00560.26930.29920.36070.24370.26840.32800.00600.00740.00960.23770.26100.31847/161/29/161816160.42930.49080.55330.00590.00630.00630.42340.48450.54700.42790.48930.55180.00590.00630.00630.42200.48300.54550.38440.43950.50200.00990.01030.01030.37450.42920.49175/811/16a3/41414120.61440.67690.73770.00670.00670.00740.60770.67020.73030.61280.67520.73590.00670.00670.00740.60610.66850.72850.55490.61740.66690.01070.01070.01140.54420.60670.65557/8111/8111090.86160.98521.10860.00780.00820.00880.85380.97701.09980.78380.89901.01200.01180.01220.01280.77200.88680.999211/413/8a11/29881.23361.35651.48150.00880.00950.00951.22481.34701.4720The Limits and Tolerances for Nominal sizes above 3/4 in. are the same as those of the corresponding size of Close Class bolt1.13701.24701.37200.01280.01350.01351.12421.23351.358515/8a13/428771.60651.72891.97890.00950.01050.01051.59701.71841.96841.49701.60261.85260.01350.01450.01451.48351.58811.838121/421/223/4366652.22542.47542.72542.97040.01170.01170.01170.01342.21372.46372.71372.95702.07692.32692.57692.79080.01570.01570.01570.01742.06122.31122.56122.7734a To be dispensed with wherever possible.BS 84:195640 BSI 02-2000Effective diameter tolerances. The tolerances for effective diameter are primarily based upon the accuracy of present day screwing tools and, starting from this basis, a general formula was derived in BS 84:1940 for these tolerances which is applicable not only to screw threads belonging to the standard series but also to any others having a reasonable combination of diameter, pitch and length of engagement.This formula is:Medium class bolt and nut tolerances on effective diameter in inches equalEffective diameter tolerances for close and normal class nuts and close and free class bolts are obtained by multiplying the values obtained from this formula by the factors stated in the paragraph headed “Classes of Tolerance”.The effective diameter tolerance given in Table 2 to Table 6 and Table 8 to Table 12 for the B.S.W. and B.S.F. series respectively, are based on a length of engagement equal to the nominal diameter of the thread, this length being approximately equal to that of a standard nut.The effective diameter tolerances given in Table 16 to Table 20 for Whitworth Special threads are based on a length of engagement of ten pitches (10p) as this length of engagement approximates to that commonly used in practice for such threads.Major diameter tolerances. Bolt. The tolerance on the major diameter of a bolt is derived from the tolerance on its effective diameter by adding to it an amount equal to 0.01p. This rule applies to all three classes of bolt.Nut. No tolerance is specified for the major diameter of a nut, but only the minimum size, which is the same as the basic major diameter. It is considered that the major diameters of nuts will be effectively controlled by the major diameters of the taps or other screwing tools used.Minor diameter tolerances. Bolt. The tolerance on the minor diameter of a bolt is related to the corresponding effective diameter tolerance, since the root of the bolt thread is formed in the same manufacturing operation as the flanks. Account is also taken of the fact that wear on the cutting or forming tool is greater on the crest of the thread than on the flanks. This is commonly allowed for in practice by making the crests of the thread on the tool to a smaller radius than the basic root radius of the bolt thread.The tolerance on the minor diameter of a bolt is derived from the tolerance on its effective diameter by adding to it an amount equal to 0.013p in the case of close class bolts and 0.02p for both medium and free class bolts.Nut. The tolerance on the minor diameter of a nut, which is the same for all classes, is as follows:Minimum depths of engagement. The bolt major diameter tolerances and the nut minor diameter tolerances provide, in conjunction with the allowance, if any, a minimum depth of engagement of approximately 50 per cent of the basic depth of the Whitworth screw thread form.where D = basic major diameter of thread in inchesLe= length of engagement in inchesp = pitch in inches.Tolerance on minor diameter of nut=0.2p + 0.004 in. for 26 t.p.i. and finer0.2p + 0.005 in. for 24 t.p.i. and 22 t.p.i.0.2p + 0.007 in. for 20 t.p.i. and coarser.0.002D30.003 Le0.005 p+ 标准分享网 w w w .b z f x w .c o m 免费下载BS 84:1956 BSI 02-200041Appendix C Tolerances on pitch and angle in relation to tolerance on effective diameter1. Effect of pitch errorsAn error in pitch virtually increases the effective diameter of a bolt and decreases the effective diameter of a nut.If p represents the maximum error in the axial displacement between any two points on a Whitworth form screw thread within the length of engagement, the corresponding virtual increase (decrease) in the effective diameter of the thread in the case of a bolt (nut) is given by the expression:Virtual change in Eff. Dia. = 1.921 p2. Effects of errors in angleAn error in one or both of the flank angles virtually increases the effective diameter of a bolt and decreases the effective diameter of a nut.If a1 and a2 represent the errors present in the two flank angles of a Whitworth form screw thread, the corresponding virtual increase (decrease) in the effective diameter of the thread in the case of a bolt (nut) is given by the following expression:3. Criterion of acceptability of a combination of errors in the effective diameter, pitch and angle of a screw threada) Bolts. The simple effective diameter of a bolt (as measured along the pitch line of the thread) should lie between the limits specified for that diameter. In addition, the virtual effective diameter (i.e. the sum of the simple effective diameter and the effective diameter equivalent of the errors present in the pitch and flank angles of the bolt) should not exceed the upper limit stated for the effective diameter.b) Nuts. The simple effective diameter of a nut (as measured along the pitch line) should lie between the limits specified for that diameter. In addition, the virtual effective diameter (i.e. the simple effective diameter after being reduced by the effective diameter equivalent of the errors present in the pitch and flank angles of the nut) should not be smaller than the lower limit stated for the effective diameter.When a bolt or nut is inspected with a GO screw gauge made to the design sizes, and a NOT GO gauge for the effective diameter made to the lower limit for the effective diameter of the bolt or the upper limit of the nut, the above conditions as regards the size of the simple effective diameter, and its size as influenced by any errors present in the pitch and flank angles of the thread are safeguarded for practical purposes.Ideally NOT GO effective diameter gauges should control only the simple effective diameter, and should not be influenced by irregularities of thread form. As ordinarily made however, they necessarily have flanks of definite length and, therefore, do not strictly control the simple effective diameter of the product thread within the minimum metal limits unless the flank angles of the product thread are correct. Such gauges will pass product threads with incorrect flank angles, the simple effective diameters of which can be outside the minimum metal limits by an amount proportional to the flank angle errors and the length of the flank of the NOT GO gauge.Flank angle errors and irregularities of thread form do not necessarily render a product thread unserviceable, but it follows that it is important to supplement the use of such NOT GO effective diameter gauges by some independent check that the form of the product thread is reasonably correct. This check can be made by supe
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