Part 1: Principles and basic data
ICS 21.040.10
NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW
BSI 2007
ISBN 978 0 580 57924 0
Publication history
First published June 1963Second edition March 1981 Third edition November 2007
Publishing and copyright information
Amendments issued since publication
The BSI copyright notice displayed in this document indicates when the document was last issued.
The following BSI references relate to the work on this standard:Draft for ment 07/ DC Committee reference FME/9
Text affeeted
Contents
Foreword iii
Annexes
Bibliography 68
List of figures
List of tables
1 Scope 12 Normative references13 4 Terms and definitions and symbols 1 Basic profile 25 General plan 59 7 Tolerances Principles and basic data 18 Basic dimensions 88 9 Tolerances Deviations for constructional threads 35 Tolerances Limits of sizes for hot-dip galvanized external screwthreads to mate with internal screw threads tapped with10 tolerance position H or G after galvanizing 53 Tolerances Limits of sizes for internal screw threads to matewith hot-dip galvanized external screw threads with maximumsize of tolerance position h before galvanizing 55
Annex A (informative) Notes for guidance 60Annex B (informative) Examples of calculations of limits of size formetric screw threads 65
Figure 1 Basic profile of ISO metric thread 3Figure 2 - Basic dimensions 8 Figure 3 Tolerance positions with respect to zero line (basic size) 19Figure 4 Internal threads with tolerance position G 21Figure 6 External threads with tolerance positions e f and g 22 Figure 5 Internal threads with tolerance position H 22Figure 7 External threads with tolerance position h 23Figure A.1 Maximum material profiles for internal and external Figure 8 External root profile 31threads 61Figure B.1 Illustration of limits of size for external thread (see Example 1) 66
Table 1 Basic profile dimensions 4Table 3 Diameter/pitch binations 6 Table 2 Maximum nominal diameter 5Table 4 Basic dimensions 9Table 5 Fundamental deviations for internal threads and extermal threads 24Table 6 Lengths of thread engagement 25 Table 7 Minor diameter tolerances of intermal threads (Tpi)26Table 8 Major diameter tolerances of external threads (7) 27Table 9 Pitch diameter tolerances of internal threads (Tp)28 Table 10 Pitch diameter tolerances of external threads (Ta2) 29Table 11 Minimum root radi 31Table 12 Remended tolerance classes for internal threads 32 Table 13 Remended tolerance classes for external threads32Table 14 Deviations 36Table 15 Deviations for hot-dip galvanized external threads 54
Table 16 External thread limits for tolerance class 6az 55Table 17 Deviations for internal threads to mate with hot-dip galvanized external threads57Table 18 Internal screw thread limits for tolerance class 6AZ 58Table 19 Internal screw thread limits for tolerance class 6AX 59 Table A.1 Nominal stress areas for extermal screw threads Coarse series63 Table A.2 Nominal stress areas for extermal screw threads Fine series 64
Summary of pages
This document prises a front cover an inside front cover pages i to iv pages 1 to 68 an inside back cover and a back cover.
Foreword
Publishinginformation
This part of BS 3643 is published by BSI and came into effecton 30 November 2007. It was prepared by Submitee SFTSE/1 Screus and fasteners technical specification mittee under the authority of Technical Committee FME/9 Nuts bolts and accessories.A list of organizations represented on this mittee can be obtainedon request to its secretary.
Supersession
This part of BS 3643 supersedes BS 3643-1:1981 which is withdrawn.
Relationshipwith otherpublications
This part of BS 3643 is based on a series of BS ISO and ISO standardsfor ISO metric general purpose screw threads each clause fromClause 4 onwards being based on one BS ISO or ISO as follows:
Clause 4: Basic profile: BS ISO 68-1:1998;*Clause 5: General plan: BS ISO 261:1998;Clause 6: Basic dimensions: ISO 724:1993; Clause 7: Tolerances Principles and basic data:BS ISO 965-1:1998;Clause 8: Tolerances Deviations for constructional screwthreads: BS ISO 965-3:1998;Clause 9: Tolerances Limits of sizes for hot-dip galvanized external screw threads to mate with internal screw threadstapped with tolerance position H or G after galvanizing:Clause 10: Tolerances Limits of sizes for hot-dip galvanized BS ISO 965-4:1998;external screw threads to mate with internal screw threads withmaximum size of tolerance position h before galvanizing: BS ISO 965-5:1998.
BS 3643 consists of the following parts:
Part 1: Principles and basic dataPart 2: Specification for selected limits of size.
BS 3643-2 specifies the fundamental deviations tolerances and limits ofand 4h 6g and 8g for external threads where appropriate for: size for the tolerances classes 4H 5H 6H and 7H for internal threads
•a course pitch series with the range 1 mm to 68 mm diameter;•a fine pitch series with the range 1 mm to 33 mm diameter;*a constant pitch series with the range 8 mm to 300 mm diameter.
