M10 x 1 Tap Drill Size
ISO metric fine · 1 mm pitch · ISO 261 / 965-1, class 6H
What size drill bit for a M10 x 1 tap?
To scale section of the tapped hole
Drill options % of thread
| Drill | Inch | mm | Thread | 6H |
|---|---|---|---|---|
| 8.9 mm | 0.3504 | 8.90 | ✗ | |
| 9 mmUse | 0.3543 | 9.00 | ✓ | |
| T | 0.3580 | 9.09 | ✓ | |
| 9.1 mm | 0.3583 | 9.10 | ✓ | |
| 23/64" | 0.3594 | 9.13 | ✓ | |
| 9.2 mm | 0.3622 | 9.20 | ✗ |
By material Aluminum, brass, mild steel: 9 mm (77%) · Stainless, tool steel: 9.1 mm (69%)
75% (orange tick) is the usual target. Hard or gummy metals like stainless are often tapped at 60 to 65% to spare the tap; aluminum, brass and plastic take 75% or a little more. The last column checks the hole against the 6H minor diameter limits (8.92 mm to 9.15 mm).
M10 x 1 ISO 261, 965-1, class 6H
| Major diameter | 10 mm / 0.3937 in |
|---|---|
| Pitch | 1 mm |
| Pitch diameter (basic) | 9.351 mm |
| Minor diameter 6H | 8.917–9.153 mm |
| Thread-forming tap drill | 9.6 mm 0.3780 in |
Clearance hole ISO 273
For a screw that passes through the part. Normal fit is the default; close fit locates the part more accurately but leaves no room for hole position error.
Hole depth rule of thumb
- 10 mmthread length for full strength in steel (1 × D)
- 15 mmin cast iron or brass (1.5 × D), up to 20 mm in aluminum
- +5 mmextra drill depth below the thread for a plug tap (5 pitches), +2 mm with a bottoming tap
Shop notes
The 1 mm pitch is the finest of the three M10 threads, and its drill is 9 mm for about 77% thread. That 9 mm is also the smallest drill that passes the 6H minor diameter check; 8.9 mm is already too tight. There is no slack on the small side.
The slack is all on the large side, and not much of it. Letter T (0.3580 in, 70%), 9.1 mm (69%) and 23/64 (0.3594 in, 67%) all pass. Letter T is the inch drill to use; 23/64 works if that is what you have. At 9.2 mm the hole leaves the limits.
Most trouble with this thread comes from drilling for the wrong M10. The 8.8 mm drill for M10 x 1.25 and the 8.5 mm for M10 x 1.5 are both well under the minimum minor diameter here, so the tap will be fighting excess material from the first turn. Read the pitch off the drawing or the bolt before reaching for a drill, because the three M10 screws look very much alike.