The tap drill for an M10 x 1 thread is a 9 mm drill (0.3543 in), which leaves about 77% of full thread with a cutting tap. The ideal hole for 75% thread is 9.03 mm, and 9 mm is the nearest standard metric drill.
| Percent of thread | Ideal hole | Nearest drill | Drill size | Thread achieved |
|---|---|---|---|---|
| 50% | 9.35 mm | 9.4 mm | 9.40 mm / 0.3701 in | 46% |
| 60% | 9.22 mm | 9.2 mm | 9.20 mm / 0.3622 in | 62% |
| 65% | 9.16 mm | 9.2 mm | 9.20 mm / 0.3622 in | 62% |
| 70% | 9.09 mm | 9.1 mm | 9.10 mm / 0.3583 in | 69% |
| 75% | 9.03 mm | 9 mm | 9.00 mm / 0.3543 in | 77% |
The drills either side of the target are 8 points of thread apart, so either is a reasonable choice. 9 mm (0.3543 in) gives 77% and a stronger but harder-to-tap thread; 9.1 mm (0.3583 in) gives 69% and less tapping torque. On M10 x 1 the choice is mostly about tap life in hard materials.
M10 x 1 is used on hydraulic fittings, banjo bolts and sensor housings where a fine adjustment or a seal is needed. Its basic pitch diameter is 9.35 mm and its tensile stress area is 64.5 mm². A bolt of this size passes through a 11.00 mm normal-fit clearance hole (ISO 273).
Example: M10 x 1 at 75% thread
Result: 9 mm (0.3543 in), 77% thread
| Major (nominal) diameter | 10.00 mm / 0.3937 in |
|---|---|
| Pitch | 1 mm |
| Basic pitch diameter (d − 0.6495·P) | 9.35 mm |
| Basic minor diameter, internal (d − 1.0825·P) | 8.92 mm |
| Tensile stress area | 64.5 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 fine sizes:
Use 9 mm (0.3543 in). It leaves 77% of full thread with a cutting tap; the ideal 75% hole is 9.03 mm. For an easier-to-tap 50% thread, 9.4 mm (0.3701 in) gives 46%.
9 mm is 0.3543 in. The nearest inch drill to the 75% target is T (0.3580 in), which gives 70% thread.
A forming tap needs a bigger hole: 9.56 mm for 65% thread, so drill 9.6 mm (0.3780 in). Forming taps work in ductile metals such as aluminum and mild steel.
For M10 x 1, 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 1.5 and M10 x 1.25 use the same sizes.
64.5 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 takes 9 mm (0.3543 in); M10 x 1.5 takes 8.5 mm (0.3346 in); M10 x 1.25 takes 8.8 mm (0.3465 in). Check the pitch on the drawing before you drill.
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