M16 tap drill size
The tap drill for M16×2 is 14 mm. That’s the standard chart size and gives about 77% of full thread.
Open in the full tap drill finder
Tap drill by thread percentage
75% is the usual workshop figure. Less thread is easier to tap; more adds little strength.
| Thread % | Ideal drill | Nearest metric drill | Nearest imperial drill |
|---|---|---|---|
| 60% | 14.441 mm 0.5685" | 14.5 mm (58%) | 9/16" 0.5625" (66%) |
| 65% | 14.311 mm 0.5634" | 14.25 mm (67%) | 9/16" 0.5625" (66%) |
| 70% | 14.181 mm 0.5583" | 14.25 mm (67%) | 9/16" 0.5625" (66%) |
| 75% | 14.051 mm 0.5532" | 14 mm (77%) | 35/64" 0.5469" (81%) |
| 80% | 13.922 mm 0.5481" | 13.9 mm (81%) | 35/64" 0.5469" (81%) |
About this size
ISO metric coarse is the default thread for general engineering in the UK and Europe. If a drawing just says “M10”, it means the coarse pitch.
- For stainless steel, duplex and other tough materials, go to about 65% thread: a 14.25 mm drill gives 67%. For mild steel, brass and cast iron the 14 mm is fine.
- For a blind hole with 1.5 × D thread engagement (24 mm), drill about 32 mm deep. That leaves room for the 3–4 tapered lead threads on a second or plug tap. In steel, 1 × D engagement is usually enough; in aluminium or cast iron allow 1.5–2 × D.
Clearance holes for M16
| Fit | Drill |
|---|---|
| Close | 17 mm (0.669") |
| Medium (normal) | 17.5 mm (0.689") |
| Free (loose) | 18.5 mm (0.728") |
Fine, medium and coarse series from ISO 273. Medium suits most jobs; use fine where parts must locate closely and coarse for quick assembly or coated bolts.
M16 thread data
| Designation | M16×2 |
|---|---|
| Standard | ISO 68-1 basic profile, ISO 261/262 series |
| Pitch | 2 mm pitch (12.7 TPI equivalent) |
| Thread angle | 60° |
| Major diameter | 16 mm (0.630") |
| Pitch (effective) diameter | 14.701 mm (0.579") |
| Minor diameter, external | 13.546 mm (0.533") |
| Minor diameter, internal | 13.835 mm (0.545") |
| Thread depth (internal) | 1.083 mm |
Basic sizes. Real screws are slightly under and real nuts slightly over these values because of tolerance classes.
Quick calculator
Nearest alternatives
If you don’t have the right drill, these give:
- 13.9 mm drill → about 81% thread
- 14 mm drill → about 77% thread
- 14.25 mm drill → about 67% thread
Other pitches of M16: M16 × 1.5.
Threads close in size (not interchangeable – the pitch and/or angle differ):
- M16 × 1.5 – 16 mm major, 1.5 mm pitch (16.9 TPI equivalent)
- 5/8" UNC – 15.88 mm major, 11 TPI (2.309 mm pitch)
- 5/8" UNF – 15.88 mm major, 18 TPI (1.411 mm pitch)
- 5/8" BSW – 15.88 mm major, 11 TPI (2.309 mm pitch)
- 5/8" BSF – 15.88 mm major, 14 TPI (1.814 mm pitch)
Questions
What size drill for a M16 tap?
The tap drill for M16×2 is 14 mm. That’s the standard chart size and gives about 77% of full thread.
What size clearance hole for M16?
For a M16 screw or bolt, drill 17 mm for a close fit, 17.5 mm for a medium (normal) fit or 18.5 mm for a free fit. These are the ISO 273 fine, medium and coarse sizes.
What is the pitch of M16?
M16×2 has a 2 mm pitch (12.7 TPI equivalent), a 60° thread angle and a 16 mm major diameter.
Sources: Chart drill: the common metric coarse tapping chart. Percent values worked out from the ISO 68-1 basic profile. Clearance holes: ISO 273 (checked 25/10/2026). Values are for reference only – check your tap maker’s chart. See the disclaimer.
Spotted a mistake? Report an error.