Printed from Kezuriba (kezuriba.net/en/threads/)
Metric tap drill size chart
Tap drill sizes for ISO metric threads, as recommended in the technical data of three Japanese tap makers. Any drill that keeps the hole inside the minor-diameter range D1 (6H) meets the thread class; where to aim inside that range differs slightly by maker.
Tap drill sizes
from three
tap makers.
⌀Metric coarse threads (cutting taps)
| Size | Pitch | D1 range (6H) | OSG | Nachi | Yamawa | d − P |
|---|---|---|---|---|---|---|
| M1.6 | 0.35 | 1.221 – 1.321 | 1.25 | 1.25 | 1.3 | 1.25 |
| M2 | 0.4 | 1.567 – 1.679 | 1.6 | 1.6 | 1.65 | 1.60 |
| M2.5 | 0.45 | 2.013 – 2.138 | 2.05 | 2.05 | 2.11 | 2.05 |
| M3 | 0.5 | 2.459 – 2.599 | 2.5 | 2.5 | 2.56 | 2.50 |
| M4 | 0.7 | 3.242 – 3.422 | 3.3 | 3.3 | 3.38 | 3.30 |
| M5 | 0.8 | 4.134 – 4.334 | 4.2 | 4.2 | 4.28 | 4.20 |
| M6 | 1 | 4.917 – 5.153 | 5 | 5 | 5.09 | 5.00 |
| M8 | 1.25 | 6.647 – 6.912 | 6.75 | 6.8 | 6.85 | 6.75 |
| M10 | 1.5 | 8.376 – 8.676 | 8.5 | 8.5 | 8.6 | 8.50 |
| M12 | 1.75 | 10.106 – 10.441 | 10.25 | 10.2 | 10.4 | 10.25 |
| M14 | 2 | 11.835 – 12.21 | 12 | 12 | 12.1 | 12.00 |
| M16 | 2 | 13.835 – 14.21 | 14 | 14 | 14.1 | 14.00 |
| M18 | 2.5 | 15.294 – 15.744 | 15.5 | 15.5 | 15.6 | 15.50 |
| M20 | 2.5 | 17.294 – 17.744 | 17.5 | 17.5 | 17.6 | 17.50 |
| M22 | 2.5 | 19.294 – 19.744 | 19.5 | 19.5 | 19.6 | 19.50 |
| M24 | 3 | 20.752 – 21.252 | 21 | 21 | 21.1 | 21.00 |
| M27 | 3 | 23.752 – 24.252 | 24 | 24 | 24.1 | 24.00 |
| M30 | 3.5 | 26.211 – 26.771 | 26.5 | 26.5 | 26.6 | 26.50 |
All values in mm. Each size page has the sources, bolt and nut sizes and counterbore dimensions.
≋Metric fine threads (cutting taps)
| Size | D1 range (6H) | OSG | Nachi | Yamawa |
|---|---|---|---|---|
| M3×0.35 | 2.621 – 2.721 | 2.65 | 2.65 | 2.7 |
| M4×0.5 | 3.459 – 3.599 | 3.5 | 3.5 | 3.56 |
| M5×0.5 | 4.459 – 4.599 | 4.5 | 4.5 | 4.56 |
| M6×0.75 | 5.188 – 5.378 | 5.25 | 5.3 | 5.33 |
| M8×1 | 6.917 – 7.153 | 7 | 7 | 7.09 |
| M8×0.75 | 7.188 – 7.378 | 7.25 | 7.3 | 7.33 |
| M10×1.25 | 8.647 – 8.912 | 8.75 | 8.8 | 8.85 |
| M10×1 | 8.917 – 9.153 | 9 | 9 | 9.09 |
| M12×1.5 | 10.376 – 10.676 | 10.5 | 10.5 | 10.6 |
| M12×1.25 | 10.647 – 10.912 | 10.75 | 10.8 | 10.85 |
| M12×1 | 10.917 – 11.153 | 11 | 11 | 11.09 |
| M14×1.5 | 12.376 – 12.676 | 12.5 | 12.5 | 12.6 |
| M16×1.5 | 14.376 – 14.676 | 14.5 | 14.5 | 14.6 |
| M16×1 | 14.917 – 15.153 | 15 | 15 | 15.09 |
| M18×2 | 15.835 – 16.21 | 16 | 16 | 16.1 |
| M18×1.5 | 16.376 – 16.676 | 16.5 | 16.5 | 16.6 |
| M20×2 | 17.835 – 18.21 | 18 | 18 | 18.1 |
| M20×1.5 | 18.376 – 18.676 | 18.5 | 18.5 | 18.6 |
| M22×2 | 19.835 – 20.21 | 20 | 20 | 20.1 |
| M22×1.5 | 20.376 – 20.676 | 20.5 | 20.5 | 20.6 |
| M24×2 | 21.835 – 22.21 | 22 | 22 | 22.1 |
| M24×1.5 | 22.376 – 22.676 | 22.5 | 22.5 | 22.6 |
| M27×2 | 24.835 – 25.21 | 25 | 25 | 25.1 |
| M27×1.5 | 25.376 – 25.676 | 25.5 | 25.5 | 25.6 |
| M30×2 | 27.835 – 28.21 | 28 | 28 | 28.1 |
| M30×1.5 | 28.376 – 28.676 | 28.5 | 28.5 | 28.6 |
Choosing a tap drill
- A smaller hole gives a fuller thread but loads the tap more and makes breakage more likely. A larger hole gives a shallower thread.
- “Percentage of thread” is defined differently by different makers. OSG Japan takes the basic engagement height (1.0825P) as 100%, while OSG USA and Sandvik Coromant take 1.299P as 100%. The same drill gives different percentages, so check which definition a table uses (OSG tap drill sizes (Japanese), Sandvik Coromant threading formulas).
- Forming (roll) taps need a larger hole than cutting taps, and each maker presents its recommendation differently. Forming-tap tables are on the Japanese pages.
- Inch and pipe threads: UNC / UNF tap drills and pipe threads (G, R, Rc, Rp) and NPT.