FREE CNC TOOL · Tap drill sizes
Tap Drill Size Chart (Metric Coarse / Fine Threads)
Enter a thread size to look up the recommended drill diameter instantly, or read the full M2–M30 chart below. Table values are standard recommendations for a cut tap at roughly 75% thread engagement.
Metric coarse thread tap drill chart
| Thread size | Pitch (mm) | Recommended drill (mm) |
|---|---|---|
| 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 |
| M27 | 3.0 | 24.0 |
| M30 | 3.5 | 26.5 |
Metric fine thread tap drill chart
| Thread size | Pitch (mm) | Recommended drill (mm) |
|---|---|---|
| M8 | 1.0 | 7.0 |
| M10 | 1.0 | 9.0 |
| M10 | 1.25 | 8.8 |
| M12 | 1.25 | 10.8 |
| M12 | 1.5 | 10.5 |
| M14 | 1.5 | 12.5 |
| M16 | 1.5 | 14.5 |
| M18 | 1.5 | 16.5 |
| M20 | 1.5 | 18.5 |
| M22 | 1.5 | 20.5 |
| M24 | 2.0 | 22.0 |
Quick formula
This formula corresponds to roughly 75% thread engagement (the standard for general mechanical use), e.g. M6×1.0 → 6 − 1.0 = 5.0mm. The listed values follow standard charts; for hard-to-machine materials such as stainless steel and titanium it is common to switch to about 65% engagement (enlarging the drill by a further 0.05–0.1mm) to lower tapping torque and the risk of tap breakage.
Table values apply to cut taps. Form (chipless) taps require a larger hole (about 5.55mm for M6). Select the hole size from the tap manufacturer's catalog; the two cannot be used interchangeably.
FAQ
What size hole do I drill to tap M6?
Coarse M6×1.0 calls for a 5.0mm drill; for fine threads apply "nominal diameter − pitch" using the relevant pitch.
Why is it recommended to open up the hole a little when tapping stainless steel?
Stainless steel work-hardens strongly and demands high tapping torque. Using about 65% thread engagement (enlarging the hole by 0.05–0.1mm) greatly reduces the chance of tap breakage, while the strength remains ample for general use.
How do I set the tapping depth for a blind hole?
Make the drilled depth about 3–5 pitches deeper than the required thread depth to leave room for chip evacuation and lead-in, and choose a spiral-flute tap suited to blind holes so chips are drawn upward.
Further reading: Complete guide to tapping and thread machining · Drilling and deep-hole machining | More tools: Cutting parameter calculator · Metal weight calculator
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