Subject: British Threads?

From: [email-masked] (Edward W Claire)
Date: 7 Nov 1995 00:18:26 GMT

I am working from some old plans which specify B.A. threads in number 
sizes-- i.e. 5 B.A., 6 B.A. etc.  Can someone give me the appropriate 
equivalents in terms of American Stamdard machine screw sizes?  Thanks.

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From: [email-masked] (Alan Frisbie)
Date: 6 Nov 95 21:39:11 PST

> equivalents in terms of American Stamdard machine screw sizes?  Thanks.

Here is my table of British, American, and Metric machine screws and
their tap drills.   This has been gleaned from a variety of sources,
none of which are guaranteed to be perfectly accurate.   In particular,
there is considerable debate over the "correct" tap drill to use, hence
some alternates are offered.   This list is sorted by outside diameter
for convenience in selecting the nearest size in another series.

I would appreciate any corrections, additions, comments, etc.

British  American  Metric   Outside     Tap   Tap Drill  Alternate  Alternate
 Sizes    Sizes    Sizes    Diameter   Drill   Diameter  Tap Drill  Tap Diam.
                            (inches)           (inches)             (inches)
=======  ========  =======  ========   =====   ========  =========  ==========
           0-80              .0600     3/64    .0469
1/16-60                      .0625     3/64    .0469
10-BA                        .0669     #54     .0550
           1-64              .0730     #53     .0595
           1-72              .0730     #53     .0595
 9-BA                        .0748     #53     .0559
           2-56              .0860     #50     .0700
           2-64              .0860     #50     .0700
 8-BA                        .0865     1.8 mm  .0709       #50       .0700
3/32-48                      .0937     #48     .0760
 7-BA                        .0983     #47     .0785
           3-48              .0990     #47     .0785
           3-56              .0990     #46     .0810       #45       .0820
 6-BA                        .1102     2.3 mm  .0905       #43       .0890
           4-40              .1120     #43     .0890       #44       .0860
           4-48              .1120     #42     .0935       #43       .0890
                   3.0-0.6   .1181     2.4 mm  .0945       3/32      .0938
                   3.0-0.5   .1181     2.5 mm  .0984       #40       .0980
1/8-40     5-40              .1250     #38     .1015
           5-44              .1250     #37     .1040
 5-BA                        .1259     #37     .1040
                   3.5-0.6   .1378     2.9 mm  .1142       #33       .1130
           6-32              .1380     #36     .1065
           6-40              .1380     #33     .1130
 4-BA                        .1417     3.0 mm  .1181       #32       .1160
                   4.0-0.75  .1575     3.2 mm  .1260       1/8       .1250
                   4.0-0.7   .1575     3.3 mm  .1299       #30       .1285
 3-BA                        .1614     #29     .1360
           8-32              .1640     #29     .1360
           8-36              .1640     #29     .1360
 2-BA                        .1850     4.0 mm  .1575       #22       .1570
3/16-24                      .1875     #27     .1440
3/16-32                      .1875     #23     .1540
          10-24              .1900     #25     .1495       #26       .1470
          10-32              .1900     #21     .1590
                   5-0.9     .1968     4.1 mm  .1614       #20       .1610
                   5-0.8     .1968     4.2 mm  .1654       #19       .1660
 1-BA                        .2086     4.5 mm  .1772       #16       .1770
          12-24              .2160     #16     .1770
          12-28              .2160     #15     .1800       #14       .1820
7/32-24                      .2187     #16     .1770
7/32-26                      .2187     #15     .1800
7/32-28                      .2187     #14     .1820
 0-BA                        .2362     5.1 mm  .2008       #7        .2010
                   6-1.0     .2362     5.0 mm  .1968       #9        .1960
1/4-20                       .2500     #9      .1960
          1/4-20             .2500     #7      .2010
1/4-26                       .2500     #4      .2090
          1/4-28             .2500     #3      .2130
                   7-1.0     .2756     6.0 mm  .2362       15/64     .2344
5/16-18                      .3125     1/4     .2500
          5/16-18            .3125     F       .2570
5/16-22                      .3125     G       .2610
          5/16-24            .3125     I (i)   .2720
5/16-26                      .3125     J       .2770
                   8-1.0     .3150     7.0 mm  .2756       I (i)     .2720
                   8-1.25    .3150     6.8 mm  .2677       H         .2660
3/8-16                       .3750     5/16    .3125
          3/8-16             .3750     5/16    .3125
3/8-20                       .3750     P       .3230
          3/8-24             .3750     Q       .3320
3/8-26                       .3750     Q       .3320
                  10-1.5     .3937     8.5 mm  .3346       Q         .3320
                  10-1.25    .3973     8.8 mm  .3465       S         .3480
                  10-1.0     .3973     9.0 mm  .3543       S         .3480
7/16-14                      .4375     23/64   .3594
          7/16-14            .4375     U       .3680
7/16-18                      .4375     3/8     .3750
          7/16-20            .4375     25/64   .3906
7/16-26                      .4375     Y       .4040
                  12-1.75    .4724     10.3 mm .4055       Y         .4040
                  12-1.5     .4724     10.5 mm .4134       Z         .4130
                  12-1.25    .4724     10.8 mm .4252       27/64     .4219
                  12-1.0     .4724     11.0 mm .4331       7/16      .4375
1/2-12                       .5000     13/32   .4062
          1/2-13             .5000     27/64   .4219
1/2-20                       .5000     7/16    .4375
          1/2-20             .5000     29/64   .4531
1/2-26                       .5000     29/64   .4531
                  14-2.0     .5512     12.0 mm .4724       15/32     .4688
                  14-1.75    .5512     12.3 mm .4842       31/64     .4844
                  14-1.5     .5512     12.5 mm .4921       1/2       .5000
                  14-1.25    .5512     12.8 mm .5039       1/2       .5000
                  14-1.0     .5512     13.0 mm .5118       33/64     .5156

--  Alan E. Frisbie               [email-masked]
--  Flying Disk Systems, Inc.
--  4759 Round Top Drive          (213) 256-2575 (voice)
--  Los Angeles, CA 90065         (213) 258-3585 (FAX)

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From: [email-masked] (Ulf Jonsson)
Date: 8 Nov 1995 02:17:17 GMT

Alan, you are a hero! thanks for the table.

Ulf