Use the below bolt hole clearance chart for Imperial size bolts and screws.
This table shows how to determine the clearance hole size for a bolt.
| Size of Screw | Clearance Hole Drills | ||||
| Close Fit |
Free Fit |
||||
| No. or Diameter | Decimal Equivalent |
Drill Size | Decimal Equivalent |
Drill Size | Decimal Equivalent |
| 0 | 0.0600 | 52 | 0.0635 | 50 | 0.0700 |
| 1 | 0.0730 | 48 | 0.0760 | 46 | 0.0810 |
| 2 | 0.0860 | 43 | 0.0890 | 41 | 0.0960 |
| 3 | 0.0990 | 37 | 0.1040 | 35 | 0.1100 |
| 4 | 0.1120 | 32 | 0.1160 | 30 | 0.1285 |
| 5 | 0.1250 | 30 | 0.1285 | 29 | 0.1360 |
| 6 | 0.1380 | 27 | 0.1440 | 25 | 0.1495 |
| 8 | 0.1640 | 18 | 0.1695 | 16 | 0.1770 |
| 10 | 0.1900 | 9 | 0.1960 | 7 | 0.2010 |
| 12 | 0.2160 | 2 | 0.2210 | 1 | 0.2280 |
| 14 | 0.2420 | D | 0.2460 | F | 0.2570 |
| 1/4 | 0.2500 | F | 0.2570 | H | 0.2660 |
| 5/16 | 0.3125 | P | 0.3230 | Q | 0.3320 |
| 3/8 | 0.3750 | W | 0.3860 | X | 0.3970 |
| 7/16 | 0.4375 | 29/64 | 0.4531 | 15/32 | 0.4687 |
| 1/2 | 0.5000 | 33/64 | 0.5156 | 17/32 | 0.5312 |
For example, an 3/8″ bolt with a close fit would have a W (0.3860) clearance hole.
Download the Imperial Clearance Hole Chart to save the chart as a PDF – useful to print out to have next to your tools.
Want to determine what size clearance hole for Metric, for example, a 10.5 mm clearance hole is required for an M10 close fit, then check out our chart here.
For more ANSI standards check out ANSI.
Reference:
- Oberg, E., Jones ,F.D., Horton H.L., Ryffel H.H., (1976). Machinery’s Handbook 20th Edition. Industrial Press Inc, 1443.