What size drill for an M10×1 tap?

9 mm (9 mm), which gives about 75% thread engagement.

What clearance hole for M10×1?

10.5 mm for a close fit — enough to pass the bolt without slop.

What spanner fits M10×1?

16 mm across the flats on a standard hex head.

M10×1 thread

M10×1 tap drill

9 mm

Clearance hole 10.5 mm · 16 mm hex

M10×1 is a fine metric thread with a 10 mm (0.394") major diameter and 1 mm pitch. Tap it with a 9 mm drill; drill 10.5 mm to pass a bolt through.

The numbers

Designation: M10×1
Major diameter: 10 mm / 0.394"
Minor diameter: 8.917 mm
Pitch: 1 mm pitch
Tap drill (75% thread): 9 mm — 9 mm
Clearance hole (close fit): 10.5 mm / 0.413"
Hex across flats: 16 mm

How to measure what you have

Measure across the thread crests with calipers. A used M10×1 reads a little under 10 mm — the crests are truncated by the standard, then worn and plated, so anything from about 9.6 mm up is consistent with this size.
Measure the pitch: put a rule against the threads and count the distance over ten crests, then divide by ten. This one should give 1 mm.
A thread pitch gauge settles it in seconds and costs very little. Guessing between a coarse and a fine thread of the same diameter is the usual way a thread gets stripped.

Tightening torque

Typical torque

46–62 N·m

33.9–45.7 lb·ft

Plain steel property class 8.8 or SAE grade 5, dry threads, tightened to about 65% of yield. Lubricated threads reach the same preload at 20-30% less torque. Where the manufacturer publishes a figure — spark plugs, wheel nuts, cylinder heads — use theirs.

Where this size turns up

Bicycle rear derailleur hanger threads
Bicycle disc brake adaptor bolts on some frames
Fine-pitch adjusters and jam nuts

Other threads at this diameter

Same diameter, different pitch. Forcing the wrong one strips the thread in a turn or two.
Thread	Pitch	Tap drill	Clearance
M10×1.5	1.5 mm	8.5 mm	10.5 mm
M10×1.25	1.25 mm	8.8 mm	10.5 mm

Common questions

What size drill for an M10×1 tap?: 9 mm (9 mm), which gives about 75% thread engagement.
What clearance hole for M10×1?: 10.5 mm for a close fit — enough to pass the bolt without slop.
What spanner fits M10×1?: 16 mm across the flats on a standard hex head.

M10×1.5 8.5 mm tap drill
M10×1.25 8.8 mm tap drill
M8×1.25 6.8 mm tap drill
M12×1.75 10.2 mm tap drill
M8×1 7 mm tap drill
M8×0.75 7.2 mm tap drill
M12×1.5 10.5 mm tap drill
M12×1.25 10.8 mm tap drill
M12×1 11 mm tap drill
M6×1 5 mm tap drill
M14×2 12 mm tap drill
M6×0.75 5.2 mm tap drill

Sources

Official vendor product documentation — At One Place
Typical range compiled from manufacturer specifications — At One Place

How these figures are compiled and checked