The tap drill for an M10 x 1.5 thread is a 8.5 mm drill (0.3346 in), which leaves about 77% of full thread with a cutting tap. The ideal hole for 75% thread is 8.54 mm, and 8.5 mm is the nearest standard metric drill.
| Percent of thread | Ideal hole | Nearest drill | Drill size | Thread achieved |
|---|---|---|---|---|
| 50% | 9.03 mm | 9 mm | 9.00 mm / 0.3543 in | 51% |
| 60% | 8.83 mm | 8.8 mm | 8.80 mm / 0.3465 in | 62% |
| 65% | 8.73 mm | 8.7 mm | 8.70 mm / 0.3425 in | 67% |
| 70% | 8.64 mm | 8.6 mm | 8.60 mm / 0.3386 in | 72% |
| 75% | 8.54 mm | 8.5 mm | 8.50 mm / 0.3346 in | 77% |
The drills either side of the target are 5 points of thread apart, so either is a reasonable choice. 8.5 mm (0.3346 in) gives 77% and a stronger but harder-to-tap thread; 8.6 mm (0.3386 in) gives 72% and less tapping torque. On M10 x 1.5 the choice is mostly about tap life in hard materials.
M10 is used for structural brackets, machine feet, lifting points and engine and suspension parts. Its basic pitch diameter is 9.03 mm and its tensile stress area is 58.0 mm². A bolt of this size passes through a 11.00 mm normal-fit clearance hole (ISO 273).
Example: M10 x 1.5 at 75% thread
Result: 8.5 mm (0.3346 in), 77% thread
| Major (nominal) diameter | 10.00 mm / 0.3937 in |
|---|---|
| Pitch | 1.5 mm |
| Basic pitch diameter (d − 0.6495·P) | 9.03 mm |
| Basic minor diameter, internal (d − 1.0825·P) | 8.38 mm |
| Tensile stress area | 58.0 mm² |
| Fit | Hole diameter |
|---|---|
| Close | 10.50 mm / 0.4134 in |
| Normal | 11.00 mm / 0.4331 in |
| Loose | 12.00 mm / 0.4724 in |
All Metric coarse sizes:
Use 8.5 mm (0.3346 in). It leaves 77% of full thread with a cutting tap; the ideal 75% hole is 8.54 mm. For an easier-to-tap 50% thread, 9 mm (0.3543 in) gives 51%.
8.5 mm is 0.3346 in. The nearest inch drill to the 75% target is R (0.3390 in), which gives 71% thread.
A forming tap needs a bigger hole: 9.34 mm for 65% thread, so drill 9.3 mm (0.3661 in). Forming taps work in ductile metals such as aluminum and mild steel.
For M10 x 1.5, ISO 273 gives close fit 10.50 mm, normal fit 11.00 mm and loose fit 12.00 mm. The hole depends only on the diameter, so M10 x 1.25 and M10 x 1 use the same sizes.
58.0 mm², from As = π/4 × (d − 0.9382 × P)². Multiply it by the bolt material's proof or tensile strength to get the load the thread can carry.
No. The drill depends on the pitch, not only the diameter. M10 x 1.5 takes 8.5 mm (0.3346 in); M10 x 1.25 takes 8.8 mm (0.3465 in); M10 x 1 takes 9 mm (0.3543 in). Check the pitch on the drawing before you drill.
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