M12 x 1.5 Tap Drill Size

ISO metric fine · 1.5 mm pitch · ISO 261 / 965-1, class 6H

What size drill bit for a M12 x 1.5 tap?

10.5 mmmetric drill

0.4134inch

10.50mm

77%thread

No 10.5 mm drill? Use Z (78%).

To scale section of the tapped hole

Drawn from the M12 x 1.5 basic profile. Hatched area is the part; the thread runs 1.5 × D and the drill goes 5 pitches deeper for a plug tap.

Drill options % of thread

Drill options for M12 x 1.5
Drill	Inch	mm	Thread	6H
10.4 mm	0.4095	10.40	82%	✓
Z	0.4130	10.49	78%	✓
10.5 mmUse	0.4134	10.50	77%	✓
10.6 mm	0.4173	10.60	72%	✓
10.7 mm	0.4213	10.70	67%	✗
27/64"	0.4219	10.72	66%	✗
10.8 mm	0.4252	10.80	62%	✗
10.9 mm	0.4291	10.90	57%	✗

By material Aluminum, brass, mild steel: 10.5 mm (77%) · Stainless, tool steel: 10.6 mm (72%)

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 (10.38 mm to 10.68 mm).

M12 x 1.5 ISO 261, 965-1, class 6H

Major diameter	12 mm / 0.4724 in
Pitch	1.5 mm
Pitch diameter (basic)	11.026 mm
Minor diameter 6H	10.376–10.676 mm
Thread-forming tap drill	11.3 mm 0.4449 in

Clearance hole ISO 273

Close13 mm13 mm

Normal13.5 mm13.5 mm

Loose14.5 mm14.5 mm

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

12 mmthread length for full strength in steel (1 × D)
18 mmin cast iron or brass (1.5 × D), up to 24 mm in aluminum
+7.5 mmextra drill depth below the thread for a plug tap (5 pitches), +3 mm with a bottoming tap

Shop notes

Drill 10.5 mm for about 77% thread. If you only have inch drills, letter Z is the same hole for practical purposes: 0.4130 in against 0.4134 in, and 78% thread. Few metric threads have a letter drill that close.

M12 x 1.5 is the thread you are most likely to meet on wheel studs and lug nuts, which is also why it gets confused with the coarse M12 x 1.75. Plain "M12" means the coarse one. The coarse thread's 10.2 mm drill is too small for this hole, and the two screws do not interchange.

The usable range is 10.4 mm (82%) to 10.6 mm (72%). At 10.7 mm you are outside the 6H minor diameter limits, and so is the 27/64 (66%), which is the drill people tend to grab because it is the tap drill for 1/2-13 and sits next to it in a fractional set. For hard steel, 10.6 mm is the sensible loose option; going beyond it saves tap torque but costs more thread than it is worth.