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BreakingChips

ISO metric · coarse

M2.5 × 0.45 tap drill size

For general work, OSG suggests 65–70% of full thread. Harder materials and deep holes want less; the calculator sets it from your material.

Cut tap

2.1 mm

0.0827" · 68% thread

Form tap

2.3 mm

0.0906" · 65% thread

Open M2.5 × 0.45 in the calculator

Pick your material for its % of thread, tapping RPM and the rigid-tap code.

Thread dimensions

Major Ø
2.500 mm (0.0984")
Pitch
0.45 mm
Pitch Ø (basic)
2.208 mm (0.0869")
Minor Ø (internal, basic)
2.013 mm (0.0792")
Thread depth (internal)
0.244 mm (0.0096")

Basic sizes of the 60° form. Tolerance classes (6H) set the limits around them.

Cut tap drills

For a cutting (fluted or spiral) tap. Every standard drill from 50% to 85% thread; suggested rows are in the 65–70% band.

Cut tap drills for M2.5 × 0.45
DrillØ inØ mmThread
#460.08102.0676%
#450.08202.0871%
2.1 mmsuggested0.08272.1068%
#440.08602.1854%
2.2 mm0.08662.2051%

Form tap drills

A form (roll) tap displaces metal instead of cutting it, so it needs a bigger hole. Every standard drill from 50% to 85% thread; suggested rows are in the 65–70% band.

Form tap drills for M2.5 × 0.45
DrillØ inØ mmThread
#430.08902.2678%
2.3 mmsuggested0.09062.3065%

3-wire measurement

Best wire size
0.260 mm (0.0102")
Over wires, at basic pitch Ø
2.597 mm (0.1023")

For the external thread (the screw). The best wire touches the flanks at the pitch diameter.

Sources