What Size Drill Bit

M7 x 1 tap drill size

6 mm

Inches
0.2362
Inch bit
Letter B
Thread
77%

Drill a 6 mm hole before cutting an M7 thread with 1 mm pitch. The rule for metric taps is diameter minus pitch.

6 mm 7 mm thread

No metric bits? A Letter B bit (0.2380 in) gives about 74% thread.

M7 x 1 thread and hole sizes

ThreadM7, 1 mm pitch, coarse
Major diameter7 mm 0.2756 in
Tap drill6 mm 0.2362 in
Closest inch bitLetter B 0.2380 in
Clearance hole, close fit7.4 mm
Clearance hole, medium fit7.6 mm

Why 6 mm

Subtract the pitch from the diameter: 7 minus 1 is 6 mm. That leaves 77% thread, the usual target for a cut tap.

More thread than that adds almost no strength and makes the tap much easier to break. In hard or tough material, go 0.1 mm larger.

Tools for this job

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