Unifiedscrew threads-
Parts1&2:Diameters1/inandlarger
Co-operatingorganizations
The Mechanical Engineering Industry Standards Committee under whosesupervision this British Standard was prepared consists of representatives from the following Government departments and scientific and industrialorganizations:
Admiralty* Air Ministry*Association of Consulting Engineers Associated Offices’ Technical Committee(Incorporated)British Chemical Plant Manufacturers’ AssociationBritish Compressed Air Society British Electrical and Allied ManufacturersBritish Engineers’ Association* Association*British Internal Combustion Engine British Gear Manufacturers’ AssociationManufacturers AssociationBritish Iron and Steel Federation British Railways The British TransportCrown Agents for Oversea Governments and CommissionD.S.L.R. - National Engineering Laboratory* Administrations*Electricity Council The Generating Board and the Area Boards in England and WalesEngineering Bquipment Users’ Association*
High Commission of India Gas CouneilInstitute of Marine EngineersInstitute of Petroleum Institute of Civil EngineersInstitution of Gas Engineers Institution of Heating and VentilatingInstitution of Mechanical Engineers* EngineersInstitution of Mechanical Engineers (Automobile Division)Institution of Production Engineers*Lootive and Allied Manufacturers' Association of Great Britain*Machine Tool Trades Association Ministry of Labour (Factory Inspectorate)Ministry of Power Ministry of TransportMinistry of Works National Coal BoardNational Physical Laboratory (D.8.I.R.) Radio Industry Couneil*War Office*
marked with an asterisk in the above list together with the following were The Government departments and scientific and industrial organizationsdirectly represented on the mittee entrusted with the preparation of thisstandard:
Society of British Aircraft Constructors Serew Thread Tool Manufacturers" AsociationTelemunication Engineering and Manufacturing AssociationIndividual Manufacturers
Agricultural Engineers’ Association British Bolt Nut Serew and Rivet FederationElectronic Engineering Association Ministry of AviationNational Association of MarineScientific Instrument Manufacturers' EnginebuildersAssociation
This British Standard having been approved by the MechanicalEngineering Industry Standards Committee and endorsed by theDivisional Council was Chairman of the Engineeringpublished under the authority of the General Couneilon September 1962
BSI 02-2000
First publisbed June 1949Second revision Parts 1 and 2 First revision November 1953September 1962
Amendments issued since publication
Amd. No. Date of issue Comments1345 January March 1979 Indicated by a sideline in the margin
The following BSI referenoesrelate to the work on this standard:Draft for ment A(MEE)9770 Committee reference MEE/1/13
ISBN 0 580 34078 3
Contents
PageForeword Co-operating organizations Inside front cover ivIntroduction 1Part 1Section 1. General 1 Seope 2 2Section 2. Thread series order of selection and sugested applications 2 ISO/Unified thread form 2 [t~3 General 74 Coarse thread series (UNC) 75 6 Fine thread series (UNF) Extra fine thread series (UNEF) 7 77 Constant pitch series 7Section 3. Screw thread classes 8 Selection of diameter/pitch binations 8 96 Thread classes 610 11 Classes 2A and 2B Classes 3A and 3B 6 612 Classes 1A and 1B 6Section 4. Screw thread tolerances allowances and limits of size 13 Coated threads 10 1214 General 1215 Tolerance zones Effective diameter tolerances 12 1216 17 Allowances 1218 External thread major diameter tolerances Internal thread minor diameter tolerances 1220 19 External thread minor diameter tolerances 12 1321 Internal thread major diameter tolerances Acceptability of threads 13Section 5. Screw thread designations 22 13 1723 Screw thread designations 10Seetion 1. General Part 2 741 Scope 74Section 2. Guidance in the selection of UNS threads with fractional 2 Decimal inch diameters of 1.4 in and larger 74inch diameter/pitch binations 753 Guidance in the selection of UNS threads with fractional inch diameter/pitch binations 75Section 3. Threads with decimal inch diameters Decimal inch diameters of 1.4 in and larger 95 4 Limits of size 76 766 inch diameter/pitch binations Guidance in the selection of UNS threads with decimal 9Section 4. Limits and tolerances for UNS threads 777 Tolerances and allowances General positions for thread classes 778 6 Effective diameter tolerances 77 77
Page10 Minor diameter tolerances 7711 12 General provisions for tolerances and allowances Coated threads 77 77Section 5. Designation of UNS threads 78Appendix A Bases of tolerances and allowances for Unified screw 13 Designation of UNS threads 78threads / inch and larger 96Appendix B Outline guide and examples for calculating limits of size of untabulated UNS screw threads 100Appendix C Notes on the production of external threads 104Appendix D Unified screw threads below 1/ inch diameter for attachment purposes and for general use in the aircraft industry 106screw threads" Parts 1 and 2 Diameters / inch and larger Appendix E Relationship between tables in BS 1580 “Unifiedand ASA B1.1:1960 “Unified screw threads” 107Appendix G General symbols Appendix F Metric Equivalents 110 112Appendix H Tolerances on pitch and angle in relation totolerance on effective diameter Figure 1 - Basic form of ISO Unified thread 114 4Figure 2 Design forms of Unified internal and external threads(maximum metal condition) Figure 3 -- Limiting profiles at erests of external threads 5 6Figure 4 - Classes of Unified screw threads - effective diametertolerance zones of finished uncoated threads Figure 5 - Classes of Unified screw threads - effective diameter 11Figure 6 Tolerance zones for Unified thread Class 1A bolt tolerance zones of threads to be coated 11and Class 1B nut 14Figure 7 Tolerance zones for Unified thread Class 2A bolt and Class 2B nut 15Figure 8 Tolerance zones for Unified thread Class 3A boltFigure 9 Unified screw threads: nomogram for effective (pitch) and Class 3B nut 16Figure 10- diameter tolerances Class 2A Crest profiles resulting from different production 66methods 105Figure 11 - Figure 12-External thread Internal thread 113 113Table 1 - Unified screw threads standard series 21Unified coarse screw threads UNC Table 2 - Unified screw threads standard series. Limits of sizeLimits and tolerancesTable 3 - External threads (Bolts). Class 1A Table 4 - Internal threads (Nuts). Class 1B 50 49Table 5 - External threads (Bolts). Class 2A 51Table 6 - Internal threads (Nuts). Class 2B Table 7 - External threads (Bolts). Class 3A 52 53Table 8 - Internal threads (Nuts). Class 3B 54Unified fine screw threads UNF Limits and tolerances
PageTable 9 -External threads (Bolts). Class 1A 55Table 10 - Internal threads (Nuts). Class 1B Table 11 - External threads (Bolts). Class 2A 56 57Table 12- Internal threads (Nuts). Class 2B 8Table 14 - Internal threads (Nuts). Class 3B Table 13 - External threads (Bolts). Class 3A 59 09Basic dimensionsTable 15 - Unified Coarse thread series UNC Table 16 - Unified Fine thread series UNF 61 62Table 17 - Unified Extra Fine thread series UNEF 63Table 18 - Unified 4-thread series 4 UN Table 19 - Unified 6-thread series 6 UN 64 65Table 20 - Unified 8-thread series 8 UN 66Table 21 - Unified 12-thread series 12 UN Table 22 - Unified 16-thread series 16 UN 67 68Table 23 - Unified 20-thread series 20 UN 70Table 24 - Unified 28-thread series 28 UN Table 25 - Unified 32-thread series 32 UN 71 72Table 26 - Thread data Unified thread form 73Table 27 - Allowances for external threads of special diameters/pitches binations (UNS threads). Classes 1A and 2A 79Table 28 Major diameter tolerances for external threads of special diameter/pitch binations (UNS threads) 08Table 29 Effective and minor diameter tolerances forexternal threads of special diameter/pitch binations. Class 1A (UNS threads) 81Table 30 Effective and minor diameter tolerances for externalthreads of special diameter/pitch binations. Class 2A (UNS threads) Table 31 -Effective and minor diameter tolerances for external 82threads of special diameter/pitch binations. Class 3A (UNS threads) Table 32 -Effective diameter tolerances for internal threads of 88special diameter/pitch binations. Class 1B (UNS threads) 84Table 33 Effective diameter tolerances for internal threads of special diameter/pitch binations. Class 2B (UNS threads) 85special diameter/pitch binations. Class 3B (UNS threads) Table 34 - Effective diameter tolerances for internal threads ofTable 35 - Minor diameter tolerances for internal threads of 98special diameter/pitch binations (UNS threads) Table 36 - Unified screw threads: decimal inch diameters 87with preferred pitches 88Table 37 Limits of size for UNS threads having decimal inch basic sizes and preferred pitches 68Table 38 Limits of size of Unified threads serew thread tolerance formulae 86
