Thread prep
Tap Drill Chart
Chart-driven tap drill and clearance reference values for common shop threads.
Last updated 2026-05-12Confidence: reference-derived18 rows
| Thread | System | Tap drill | Decimal / mm | Normal clearance |
|---|---|---|---|---|
| #6-32 | UNC | #36 | 0.1065 in / 2.705 mm | 0.1495 in |
| #8-32 | UNC | #29 | 0.136 in / 3.454 mm | 0.177 in |
| #10-24 | UNC | #25 | 0.1495 in / 3.797 mm | 0.201 in |
| #10-32 | UNF | #21 | 0.159 in / 4.039 mm | 0.201 in |
| 1/4-20 | UNC | #7 | 0.201 in / 5.105 mm | 0.266 in |
| 1/4-28 | UNF | #3 | 0.213 in / 5.41 mm | 0.266 in |
| 5/16-18 | UNC | F | 0.257 in / 6.528 mm | 0.332 in |
| 3/8-16 | UNC | 5/16 | 0.3125 in / 7.938 mm | 0.397 in |
| 1/2-13 | UNC | 27/64 | 0.4219 in / 10.716 mm | 0.531 in |
| M3 x 0.5 | METRIC_COARSE | 2.5 mm | 0.0984 in / 2.5 mm | 3.4 mm |
| M4 x 0.7 | METRIC_COARSE | 3.3 mm | 0.1299 in / 3.3 mm | 4.5 mm |
| M5 x 0.8 | METRIC_COARSE | 4.2 mm | 0.1654 in / 4.2 mm | 5.5 mm |
| M6 x 1.0 | METRIC_COARSE | 5 mm | 0.1969 in / 5 mm | 6.6 mm |
| M8 x 1.25 | METRIC_COARSE | 6.8 mm | 0.2677 in / 6.8 mm | 9 mm |
| M10 x 1.5 | METRIC_COARSE | 8.5 mm | 0.3346 in / 8.5 mm | 11 mm |
| M12 x 1.75 | METRIC_COARSE | 10.2 mm | 0.4016 in / 10.2 mm | 13.5 mm |
| M10 x 1.25 | METRIC_FINE | 8.8 mm | 0.3465 in / 8.8 mm | 11 mm |
| M12 x 1.5 | METRIC_FINE | 10.5 mm | 0.4134 in / 10.5 mm | 13.5 mm |