Threads and Threading - Sportpilot.info

Machinery's Handbook 27th Edition
METRIC SCREW THREADS M PROFILE 1797
Tolerance Grade Comparisons.—The approximate ratios of the tolerance grades shown
in Tables 8, 9, 10, and 11 in terms of Grade 6 are as follows:
Minor Diameter Tolerance of Internal Thread: T D1 (Table 8): Grade 4 is 0.63 T D1 (6);
Grade 5 is 0.8 T D1 (6); Grade 7 is 1.25 T D1 (6); and Grade 8 is 1.6 T D1 (6).
Pitch Diameter Tolerance of Internal Thread: T D2 (Table 10): Grade 4 is 0.85 T d2 (6);
Grade 5 is 1.06 T d2 (6); Grade 6 is 1.32 T d2 (6); Grade 7 is 1.7 T d2 (6); and Grade 8 is 2.12
T d2 (6). It should be noted that these ratios are in terms of the Grade 6 pitch diameter tolerance
for the external thread.
Major Diameter Tolerance of External Thread: T d (Table 9): Grade 4 is 0.63 T d (6); and
Grade 8 is 1.6 T d (6).
Pitch Diameter Tolerance of External Thread: T d2 (Table 11): Grade 3 is 0.5 T d2 (6);
Grade 4 is 0.63 T d2 (6); Grade 5 is 0.8 T d2 (6); Grade 7 is 1.25 T d2 (6); Grade 8 is 1.6 T d2 (6);
and Grade 9 is 2 T d2 (6).
Standard M Profile Screw Threads, Limits of Size.—The limiting M profile for internal
threads is shown in Fig. 6 with associated dimensions for standard sizes in Table 12.
The limiting M profiles for external threads are shown in Fig. 7 with associated dimensions
for standard sizes in Table 13.
If the required values are not listed in these tables, they may be calculated using the data
in Tables 3, 6, 7, 8, 9, 10, and 11 together with the preceding formulas. If the required data
are not included in any of the tables listed above, reference should be made to Sections 6
and 9.3 of ANSI/ASME B1.13M, which gives design formulas.
Fig. 6. Internal Thread — Limiting M Profile. Tolerance Position H
*This dimension is used in the design of tools, etc. For internal threads it is not normally specified.
Generally, major diameter acceptance is based on maximum material condition gaging.
Copyright 2004, Industrial Press, Inc., New York, NY