How to Choose the Right Drill Size for Threads
Selecting the correct drill size for a threaded hole is crucial to achieving a proper thread fit. A hole that is too small will make tapping difficult, while a hole that is too large will weaken the threaded connection.
Recommended Drill Sizes for Metric Threads
The table below shows recommended drill diameters for metric threads from M1 to M24:
| Thread | Pitch [mm] | Drill Diameter [mm] |
|---|---|---|
| M1 | 0.25 | 0.75 |
| M1.2 | 0.25 | 0.95 |
| M1.6 | 0.35 | 1.25 |
| M2 | 0.4 | 1.6 |
| M2.5 | 0.45 | 2.05 |
| M3 | 0.5 | 2.5 |
| M4 | 0.7 | 3.3 |
| M5 | 0.8 | 4.2 |
| M6 | 1.0 | 5.0 |
| M8 | 1.25 | 6.8 |
| M10 | 1.5 | 8.5 |
| M12 | 1.75 | 10.2 |
| M14 | 2.0 | 12.0 |
| M16 | 2.0 | 14.0 |
| M18 | 2.5 | 15.5 |
| M20 | 2.5 | 17.5 |
| M22 | 2.5 | 19.5 |
| M24 | 3.0 | 21.0 |
Practical Tips
- Use a sharp drill bit for precise holes
- Cool the workpiece when drilling stainless steel
- Use cutting fluid for better thread quality
- Check the hole diameter before tapping the thread
Applications for Sheet Metal
For sheet metal components, the thread should be cut after cutting and bending the part. For sheets thinner than 2mm, it is recommended to use welded or riveted nuts instead of cutting threads directly into the material.