M16 tap drill size
The tap drill for an M16 × 2 metric coarse thread is 14 mm (0.5512 in). It leaves about 77 % thread, the normal range for steel.
Choose a drill
Each option redraws the section above with the thread it would leave.
M16 thread data
How much thread you need
Thread percentage to aim for by material.
Bars run from 50 % to 90 % thread. Typical shop practice for cut taps. Harder, tougher materials take less thread to save the tap; soft materials need more engagement to hold.
How the percentage is worked out
- D
- 16 mm, major diameter
- drill
- 14 mm
- P
- 2 mm pitch
Why not 100 %?
Going from 75 % to 100 % thread adds only about 5 % strength but roughly triples the torque needed to turn the tap. That is why the standard drill leaves 70–80 %.
For cut taps the quick rule is drill = major diameter − pitch. Form (roll) taps displace metal instead of cutting it and need a larger hole, roughly D − 0.5 P; check the tap maker's chart.
Other metric coarse threads
Common questions
What size drill for an M16 × 2 tap?
Use a 14 mm drill. It leaves about 77 % thread engagement.
What is 14 mm in inches?
14 mm is 0.5512 inch.
What size clearance hole for M16?
ISO 273 gives 17 mm for a close fit, 17.5 mm normal and 18.5 mm loose.
How tight should an M16 bolt be?
About 218 N·m for class 8.8 with dry threads.