BS 1936-1:1952

Co-operating organization
Foreword
Introductory notes
1 Scope
2 Form of undercut
3 Limits of tolerance on diameters of undercuts
4 Thread runouts on external threads
5 Thread runouts on internal threads: recommended hole
  tapping practice
6 Designation of undercuts and thread runouts
Appendix - Formulae for calculating widths of undercuts
           And thread runouts

Provides data of dimensions and profiles of machined undercuts for external and internal threads of Unified, Whitworth, B.A. and Cycle thread forms. Dimensions and tolerances are given for standard cutting tools for this purpose and recommendations are made of widths of undercuts and runouts for various production requirements.

This British Standard relates to dimensions for profile and width of undercuts for external and internal threads of Unified, Whitworth, B.A. and Cycle thread forms and provides for a series of standard tools for producing the undercuts recommended. It makes recommendations concerning practice in regard to undercuts and relates also to allowances for thread runouts. It includes the following:–

1. Nominal widths of machined undercuts and thread runouts (washout threads) produced from screwing tools.
2. Recommendations for minimum widths of undercut or runout for various production requirements.
3. Limits of tolerance on diameters of undercuts.
4. Standard tools for undercuts.
5. Formulae for calculating widths of undercuts and runouts. (See Appendix.)