| These tables have been reproduced here for the convienience of Model Engineers. They are used entirely at your own risk. No responsibilty can be accepted for any problems caused in their use. The tapping drills recommended will give approx 75% depth of thread. |
| SWG Thickness | |||
| Gauge | Ins (approx) | Ins (approx) | Metric (approx) |
| 4swg | 0.232" | 5.89mm | 6.0mm |
| 6swg | 0.192" | 4.88mm | 5.0mm |
| 8swg | 0.160 | 4.06mm | 4.0mm |
| 10swg | 0.128" | 1/8" | 3.0mm |
| 12swg | 0.104" | 2.64mm | 2.5mm |
| 13swg | 0.092" | 3/32" | 2.4mm |
| 14swg | 0.080" | 2.03mm | 2.0mm |
| 16swg | 0.064" | 1/16" | 1.6mm |
| 18swg | 0.048" | 3/64" | 1.2mm |
| 20swg | 0.038" | n/a | 1.0mm |
| 22swg | 0.028" | 1/32" | 0.8mm |
| 24swg | 0.022" | n/a | 0.6mm |
| 26swg | 0.018" | n/a | 0.45mm |
| 28swg | 0.0148" | 1/64" | 0.40mm |
| Brass Threads | |||||
| Size inches | Threads/in | Tapping Drill | Clearance Drill | ||
| mm. | No/Letter | mm. | No/Letter | ||
| 1/4 | 26 | 5.6 | 2 | 6.6 | G |
| 9/32 | 26 | 6.35 | E | 7.5 | M |
| 5/16 | 26 | 7.15 | K | 8.2 | P |
| 3/8 | 26 | 8.8 | S | 9.8 | W |
| 7/16 | 26 | 10.3 | Y | 11.5 | 29/64 |
| 1/2 | 26 | 11.9 | 15/32 | 13.1 | 33/64 |
| BSW Threads | |||||
| Size inches | Threads/in | Tapping Drill | Clearance Drill | ||
| mm. | No/Letter | mm. | No/Letter | ||
| 1/16 | 60 | 1.15 | 58 | 1.70 | 49 |
| 3/32 | 48 | 1.9 | 49 | 2.5 | 36 |
| 1/8 | 40 | 2.6 | 38 | 3.3 | 29 |
| 5/32 | 32 | 3.2 | 31 | 4.1 | 19 |
| 3/16 | 24 | 3.8 | 26 | 4.9 | 9 |
| 7/32 | 24 | 4.6 | 15 | 5.7 | 1 |
| 1/4 | 20 | 5.2 | 7 | 6.5 | G |
| 5/16 | 18 | 6.6 | F | 8.2 | P |
| 3/8 | 16 | 8.0 | O | 9.8 | W |
| 7/16 | 14 | 9.3 | U | 11.5 | 29/64 |
| 1/2 | 12 | 10.7 | 27/64 | 13.1 | 33/64 |
| BSF Threads | |||||
| Size inches | Threads/in | Tapping Drill | Clearance Drill | ||
| mm. | No/Letter | mm. | No/Letter | ||
| 3/16 | 28 | 4.0 | 4.9 | ||
| 7/32 | 28 | 4.7 | 14 | 5.7 | 1 |
| 1/4 | 26 | 5.4 | 3 | 6.5 | G |
| 9/32 | 26 | 6.2 | C | 7.4 | M |
| 5/16 | 22 | 6.9 | H | 8.2 | P |
| 3/8 | 20 | 8.3 | 21/64 | 9.8 | W |
| 7/16 | 18 | 9.8 | W | 11.5 | 29/64 |
| 1/2 | 16 | 11.1 | 7/16 | 13.1 | 33/64 |
| ME Threads | |||||
| Size inches | Threads/In | Tapping Drill | Clearance Drill | ||
| mm. | No/Letter | mm. | No/Letter | ||
| 1/8 | 40 | 2.6 | 38 | 3.5 | 29 |
| 5/32 | 40 | 3.3 | 30 | 4.2 | 19 |
| 3/16 | 40 | 4.1 | 20 | 5.0 | 9 |
| 7/32 | 40 | 5.0 | 9 | 5.8 | 1 |
| 1/4 | 40 | 5.8 | 1 | 6.6 | G |
| 9/32 | 32 | 6.35 | E | 7.5 | M |
| 5/16 | 32 | 7.15 | 9/32 | 8.2 | P |
| 3/8 | 32 | 8.75 | 11/32 | 9.8 | W |
| 7/16 | 26 | 10.1 | X | 11.5 | 29/64 |
| 1/2 | 26 | 11.9 | 15/32 | 13.1 | 33/64 |
| BA Threads | ||||||||
| Number | Outside Diameter | Thread Pitch | Tapping Drill | Clearance Drill | ||||
| mm | Ins | mm | Threads/In | mm | No/Letter | mm | No/Letter | |
| 0 | 6.0 | 0.236 | 1.00 | 25.4 | 5.1 | 7 | 6.2 | D |
| 1 | 5.3 | 0.209 | 0.90 | 28.2 | 4.5 | 16 | 5.5 | 2 |
| 2 | 4.7 | 0.185 | 0.81 | 31.4 | 4.0 | 22 | 4.9 | 10 |
| 3 | 4.1 | 0.161 | 0.73 | 34.8 | 3.5 | 29 | 4.2 | 19 |
| 4 | 3.6 | 0.142 | 0.66 | 38.5 | 3.0 | 31 | 3.7 | 26 |
| 5 | 3.2 | 0.126 | 0.59 | 43.0 | 2.7 | 36 | 3.3 | 30 |
| 6 | 2.8 | 0.110 | 0.53 | 47.9 | 2.35 | 42 | 2.9 | 32 |
| 7 | 2.5 | 0.098 | 0.48 | 52.9 | 2.1 | 45 | 2.6 | 38 |
| 8 | 2.2 | 0.087 | 0.43 | 59.1 | 1.8 | 50 | 2.3 | 42 |
| 9 | 1.9 | 0.075 | 0.39 | 65.1 | 1.5 | 53 | 2.0 | 47 |
| 10 | 1.7 | 0.067 | 0.35 | 72.6 | 1.4 | 54 | 1.8 | 50 |
| 11 | 1.5 | 0.059 | 0.31 | 81.9 | 1.2 | 56 | 1.6 | 52 |
| 12 | 1.3 | 0.051 | 0.28 | 90.9 | 1.05 | 59 | 1.4 | 54 |
| 13 | 1.2 | 0.047 | 0.25 | 102.0 | 0.95 | 62 | 1.3 | 55 |
| 14 | 1.0 | 0.039 | 0.23 | 109.9 | 0.8 | 68 | 1.1 | 57 |
| 15 | 0.9 | 0.035 | 0.21 | 120.5 | 0.7 | 70 | 1.0 | 60 |
| 16 | 0.79 | 0.031 | 0.19 | 133.3 | 0.6 | 73 | 0.9 | 65 |
| Decimal Equivalents Fractions of an inch expressed as decimals and millimetres | |||||
| Fractional Inch | Decimal Inch | mm. | Fractional Inch | Decimal Inch | mm. |
| 1/64 | 0.015625 | 0.3969 | 33/64 | 0.515625 | 13.0969 |
| 1/32 | 0.03125 | 0.7938 | 17/32 | 0.53125 | 13.4938 |
| 3/64 | 0.046875 | 1.1906 | 35/64 | 0.546875 | 13.8906 |
| 1/16 | 0.0625 | 1.5875 | 9/16 | 0.5625 | 14.2875 |
| 5/64 | 0.078125 | 1.9844 | 37/64 | 0.578125 | 14.6844 |
| 3/32 | 0.09375 | 2.3813 | 19/32 | 0.59375 | 15.0813 |
| 7/64 | 0.109375 | 2.7781 | 39/64 | 0.609375 | 15.4781 |
| 1/8 | 0.125 | 3.1750 | 5/8 | 0.625 | 15.8750 |
| 9/64 | 0.140625 | 3.5719 | 41/64 | 0.640625 | 16.2719 |
| 5/32 | 0.15625 | 3.9688 | 21/32 | 0.65625 | 16.6688 |
| 11/64 | 0.171875 | 4.3656 | 43/64 | 0.671875 | 17.0656 |
| 3/16 | 0.1875 | 4.7625 | 11/16 | 0.6875 | 17.4625 |
| 13/64 | 0.203125 | 5.1594 | 45/64 | 0.703125 | 17.8594 |
| 7/32 | 0.21875 | 5.5563 | 23/32 | 0.71875 | 18.2563 |
| 15/64 | 0.234375 | 5.9531 | 47/64 | 0.734375 | 18.6531 |
| 1/4 | 0.25 | 6.3500 | 3/4 | 0.75 | 19.0500 |
| 17/64 | 0.265625 | 6.7469 | 49/64 | 0.765625 | 19.4469 |
| 9/32 | 0.28125 | 7.1438 | 25/32 | 0.78125 | 19.8438 |
| 19/64 | 0.296875 | 7.5406 | 51/64 | 0.796875 | 20.2406 |
| 5/16 | 0.3125 | 7.9375 | 13/16 | 0.8125 | 20.6375 |
| 21/64 | 0.328125 | 8.3344 | 53/64 | 0.828125 | 21.0344 |
| 11/32 | 0.34375 | 8.7313 | 27/32 | 0.84375 | 21.4313 |
| 23/64 | 0.359375 | 9.1281 | 55/64 | 0.859375 | 21.8281 |
| 3/8 | 0.375 | 9.5250 | 7/8 | 0.875 | 22.2250 |
| 25/64 | 0.390625 | 9.9219 | 57/64 | 0.890625 | 22.6219 |
| 13/32 | 0.40625 | 10.3188 | 29/32 | 0.90625 | 23.0188 |
| 27/64 | 0.421875 | 10.7156 | 59/64 | 0.921875 | 23.4156 |
| 7/16 | 0.4375 | 11.1125 | 15/16 | 0.9375 | 23.8125 |
| 29/64 | 0.453125 | 11.5094 | 61/64 | 0.953125 | 24.2094 |
| 15/32 | 0.46875 | 11.9063 | 31/32 | 0.96875 | 24.6063 |
| 31/64 | 0.484375 | 12.3031 | 63/64 | 0.984375 | 25.0031 |
| 1/2 | 0.5 | 12.7000 | 1 | 1.0 | 25.4000 |