METRICfine60° flank

M12 × 1.25 fine Thread Dimensions

M12 x 1.25 (fine) is a fine pitch METRIC thread. Pitch is 1.25 mm, equivalent to 20.32 threads per inch. The recommended tap drill leaves roughly 75% thread engagement.

Nominal Ø12 mm
Pitch1.25 mm
Threads per inch20.32
Pitch Ø11.19 mm
Tap drill10.75 mm

Thread profile

millimetres unless stated
Thread profile — M12 x 1.25 (fine)d 12d2 11.19d3 10.47mm60°P 1.25h3 0.77tap ⌀10.75
M12 × 1.25 fine — basic profile60° flank angle · Not to scale
Designation
M12 x 1.25 (fine)
Thread system
METRIC
Series
fine
Flank angle
60°
Major diameter
12 mm / 0.47"
Pitch
1.25 mm
Threads per inch
20.32
Pitch diameter
11.19 mm
Minor diameter (external)
10.47 mm
Minor diameter (internal)
10.65 mm
Thread depth
0.77 mm
Recommended tap drill
Ø 10.75 mm / 0.42"

How these values are derived

Basic ISO thread geometry uses the fundamental triangle height H = 0.866025 × P. External minor diameter d₃ = d − 1.226869 × P, internal minor diameter D₁ = d − 1.082532 × P. Tap drill is given as nominal diameter minus pitch, which approximates a 75% thread engagement — adjust for tough materials or deep holes.