M12 tap drill size

Drill a 10.2 mm hole (0.4016") for an M12 × 1.75 tap. That leaves about 79% thread, the standard for general-purpose tapping.

Tap drill
10.2 mm
0.4016" · 10.20 mm · 79% thread
Inch drill
Y 76% thread
Clearance (close)
13.0 mm
Helicoil (STI) drill
12.4 mm
M12 tap drill: 10.2 mm (0.4016 in / 10.20 mm), 79% thread
Charts disagree on this size. 10.2 mm gives about 79% thread; 10.3 mm gives about 75% and is easier on the tap. Both are in published charts.

M12 thread specs

SeriesISO metric coarse
Major diameter12.00 mm (0.4724")
Pitch1.75 mm (14.5 TPI)
Basic minor diameter10.11 mm (0.3979")
Common internal class6H

Every drill that works for M12

Drills from all four sets that give 50–85% thread, largest first. Lower percentages tap easier; see how much thread you need.

DrillThreadinmmSetGood for
10.8 mm53%0.425210.80Metricdeep holes only
27/64"56%0.421910.72Fractionaldeep holes only
10.7 mm57%0.421310.70Metricdeep holes only
10.6 mm62%0.417310.60Metrichard or tough metals
10.5 mm66%0.413410.50Metrichard or tough metals
Z66%0.413010.49Letterhard or tough metals
10.4 mm70%0.409410.40Metricgeneral use
13/32"74%0.406310.32Fractionalgeneral use
10.3 mm75%0.405510.30Metricgeneral use
Y76%0.404010.26Lettergeneral use
10.2 mmstandard79%0.401610.20Metricgeneral use
10.1 mm84%0.397610.10Metricmore torque, more broken taps
X84%0.397010.08Lettermore torque, more broken taps

M12 clearance hole

The hole a M12 screw passes through. ISO 273 fine, medium and coarse series.

Fitmmin
Close (fine)13.0 mm0.5118
Normal (medium)13.5 mm0.5315
Loose (coarse)14.5 mm0.5709

M12 counterbore and countersink

For a socket head cap screw to sit flush, and for a flat head socket screw.

Socket head counterboreDiameterDepth
NBK20.00 mm13.00 mm
AMES19.25 mm12.00 mm

Flat head socket screw: countersink at 90° (metric screws, ISO 10642) to 26.88 mm (1.0583") across for a flush head. Inch flat heads use 82°, so don't mix countersinks.

M12 holes in a 3D print

Printed holes usually come out undersize. Model the hole at the drill size plus what your printer loses, then tap or drill to size. Why printed holes shrink.

Print a test hole, measure it with calipers, enter the difference. 0 models the nominal size.

Hole to tap
10.20 mm
Clearance hole
13.00 mm

M12 thread repair (Helicoil)

Stripped M12 thread? Drill out with the STI drill, tap with a M12 × 1.75 STI tap, and fit a wire thread insert. The drill in your repair kit’s instructions wins over any chart.

ChartSTI drillinmm
MISUMI12.4 mm0.488212.40

Related sizes

M10next size downM16next size up1/2-13closest inchFull chartmetric coarse

Frequently asked questions

What size drill do I use for an M12 tap?
Use a 10.2 mm (10.20 mm / 0.4016 in) drill. It leaves about 79% thread, the standard for general-purpose tapping.
What inch drill can I use for an M12 tap?
Y (10.26 mm / 0.4040 in) is the closest, giving about 76% thread. Anything from about 65% to 80% thread taps well in most materials.
What size clearance hole for an M12 screw?
13.0 mm (13.00 mm) for a close fit, 13.5 mm (13.50 mm) for a normal fit.
Is the M12 tap drill 10.2 mm or 10.3 mm?
Both appear in published charts. 10.2 mm gives about 79% thread; 10.3 mm gives about 75%, which is easier to tap. 10.2 mm is the ISO chart value (~79% thread); 10.3 mm gives ~75% thread.
What is the inch equivalent of M12?
1/2-13 is the closest size (12.70 mm vs 12.00 mm major diameter). The pitches differ, so the screws and tapped holes are not interchangeable.

Sources

Spotted a wrong number? Email contact@clove3d.com and it gets fixed.

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% thread = (major − drill) ÷ (1.299 × pitch) × 100. The standard drill comes from published charts and is checked against this formula on every build.