Clearance Hole Sizes
Find standard clearance hole sizes for machine screws and bolts.
Metric Screw Clearance Holes
| Screw Size | Normal Clear (mm) | Normal Clear (inches) | Close Fit (mm) | Loose Fit (mm) |
|---|---|---|---|---|
| M1.6 | 1.9 | 0.075 | 1.7 | 2.1 |
| M2 | 2.4 | 0.094 | 2.2 | 2.6 |
| M2.5 | 3.0 | 0.118 | 2.8 | 3.2 |
| M3 | 3.4 | 0.134 | 3.2 | 3.6 |
| M4 | 4.5 | 0.177 | 4.3 | 4.8 |
| M5 | 5.5 | 0.217 | 5.3 | 5.8 |
| M6 | 6.6 | 0.260 | 6.4 | 7.0 |
| M8 | 9.0 | 0.354 | 8.7 | 9.5 |
| M10 | 11.0 | 0.433 | 10.7 | 11.5 |
| M12 | 13.5 | 0.531 | 13.0 | 14.0 |
BA Thread Clearance Holes
| BA Size | Clearance (mm) | Clearance (inches) | Numbered Drill | Close Fit (mm) |
|---|---|---|---|---|
| BA 0 | 6.5 | 0.256 | No. 26 | 6.2 |
| BA 1 | 5.8 | 0.228 | No. 34 | 5.5 |
| BA 2 | 5.0 | 0.197 | No. 38 | 4.8 |
| BA 3 | 4.5 | 0.177 | No. 39 | 4.2 |
| BA 4 | 4.0 | 0.157 | No. 43 | 3.8 |
| BA 5 | 3.5 | 0.138 | No. 48 | 3.2 |
| BA 6 | 3.0 | 0.118 | No. 50 | 2.8 |
| BA 7 | 2.6 | 0.102 | No. 52 | 2.4 |
| BA 8 | 2.3 | 0.091 | No. 53 | 2.1 |
| BA 9 | 2.0 | 0.079 | No. 55 | 1.8 |
| BA 10 | 1.9 | 0.075 | No. 56 | 1.7 |
| BA 11 | 1.6 | 0.063 | No. 60 | 1.4 |
Imperial Screw Clearance Holes
| Screw Size | Normal Clear (inches) | Normal Clear (mm) |
|---|---|---|
| No. 0 (0.06") | 0.070 | 1.8 |
| No. 2 (0.086") | 0.100 | 2.5 |
| No. 4 (0.112") | 0.125 | 3.2 |
| No. 6 (0.138") | 0.156 | 4.0 |
| No. 8 (0.164") | 0.188 | 4.8 |
| 1/4" | 0.281 | 7.1 |
| 5/16" | 0.344 | 8.7 |
| 3/8" | 0.406 | 10.3 |
Clearance Hole Guidelines
- Normal Clearance: Standard fit for general assembly
- Close Fit: Minimal clearance, use for precision work
- Loose Fit: Larger clearance, for quick assembly or misalignment allowance
- Tap & Clearance Rule: Clearance hole ≈ 1.1-1.2 × Major diameter