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They are used entirely at your own risk.
No responsibilty can be accepted for any problems caused in their use.
Some useful tables

SWG   Brass   BSW   BSF   ME   BA   Decimal Equivalents   Click on a table name to go directly to that table

These tapping drills are recommended for use on steel only and will give approx 75% depth of thread

SWG Thickness
GaugeIns (approx)Ins (approx)Metric (approx)
4swg0.232"5.89mm6.0mm
6swg0.192"4.88mm5.0mm
8swg0.1604.06mm4.0mm
10swg0.128"1/8"3.0mm
12swg0.104"2.64mm2.5mm
13swg0.092"3/32"2.4mm
14swg0.080"2.03mm2.0mm
16swg0.064"1/16"1.6mm
18swg0.048"3/64"1.2mm
20swg0.038"n/a1.0mm
22swg0.028"1/32"0.8mm
24swg0.022"n/a0.6mm
26swg0.018"n/a0.45mm
28swg0.0148"1/64"0.40mm


Brass Threads
Size inchesThreads/inTapping DrillClearance Drill
 mm.No/Lettermm.No/Letter
1/4265.626.6G
9/32266.35E7.5M
5/16267.15K8.2P
3/8268.8S9.8W
7/162610.3Y11.529/64
1/22611.915/3213.133/64



BSW Threads
Size inchesThreads/inTapping DrillClearance Drill
 mm.No/Lettermm.No/Letter
1/16601.15581.7049
3/32481.9492.536
1/8402.6383.329
5/32323.2314.119
3/16243.8264.99
7/32244.6155.71
1/4205.276.5G
5/16186.6F8.2P
3/8168.0O9.8W
7/16149.3U11.529/64
1/21210.727/6413.133/64



BSF Threads
Size inchesThreads/inTapping DrillClearance Drill
 mm.No/Lettermm.No/Letter
3/16284.04.9
7/32284.7145.71
1/4265.436.5G
9/32266.2C7.4M
5/16226.9H8.2P
3/8208.321/649.8W
7/16189.8W11.529/64
1/21611.17/1613.133/64


ME Threads
Size inchesThreads/InTapping DrillClearance Drill
 mm.No/Lettermm.No/Letter
1/8402.6383.529
5/32403.3304.219
3/16404.1205.09
7/32405.095.81
1/4405.816.6G
9/32326.35E7.5M
5/16327.159/328.2P
3/8328.7511/329.8W
7/162610.1X11.529/64
1/22611.915/3213.133/64


BA Threads
NumberOutside DiameterThread PitchTapping DrillClearance Drill
 mmInsmmThreads/InmmNo/LettermmNo/Letter
06.00.2361.0025.45.176.2D
15.30.2090.9028.24.5165.52
24.70.1850.8131.44.0224.910
34.10.1610.7334.83.5294.219
43.60.1420.6638.53.0313.726
53.20.1260.5943.02.7363.330
62.80.1100.5347.92.35422.932
72.50.0980.4852.92.1452.638
82.20.0870.4359.11.8502.342
91.90.0750.3965.11.5532.047
101.70.0670.3572.61.4541.850
111.50.0590.3181.91.2561.652
121.30.0510.2890.91.05591.454
131.20.0470.25102.00.95621.355
141.00.0390.23109.90.8681.157
150.90.0350.21120.50.7701.060
160.790.0310.19133.30.6730.965




Decimal Equivalents
Fractions of an inch expressed as decimals and millimetres
Fractional
Inch
Decimal
Inch
mm.Fractional
Inch
Decimal
Inch
mm.
1/640.0156250.3969 33/640.51562513.0969
1/320.031250.7938 17/320.5312513.4938
3/640.0468751.1906 35/640.54687513.8906
1/160.06251.5875 9/160.562514.2875
5/640.0781251.9844 37/640.57812514.6844
3/320.093752.3813 19/320.5937515.0813
7/640.1093752.7781 39/640.60937515.4781
1/80.1253.1750 5/80.62515.8750
9/640.1406253.5719 41/640.64062516.2719
5/320.156253.9688 21/320.6562516.6688
11/640.1718754.3656 43/640.67187517.0656
3/160.18754.7625 11/160.687517.4625
13/640.2031255.1594 45/640.70312517.8594
7/320.218755.5563 23/320.7187518.2563
15/640.2343755.9531 47/640.73437518.6531
1/40.256.3500 3/40.7519.0500
17/640.2656256.7469 49/640.76562519.4469
9/320.281257.1438 25/320.7812519.8438
19/640.2968757.5406 51/640.79687520.2406
5/160.31257.9375 13/160.812520.6375
21/640.3281258.3344 53/640.82812521.0344
11/320.343758.7313 27/320.8437521.4313
23/640.3593759.1281 55/640.85937521.8281
3/80.3759.5250 7/80.87522.2250
25/640.3906259.9219 57/640.89062522.6219
13/320.4062510.3188 29/320.9062523.0188
27/640.42187510.7156 59/640.92187523.4156
7/160.437511.1125 15/160.937523.8125
29/640.45312511.5094 61/640.95312524.2094
15/320.4687511.9063 31/320.9687524.6063
31/640.48437512.3031 63/640.98437525.0031
1/20.512.7000 11.025.4000