M16 × 1.5 tap drill size
The tap drill for M16×1.5 fine is 14.5 mm. That’s the standard chart size and gives about 77% of full thread.
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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% | 14.831 mm 0.5839" | 14.75 mm (64%) | 37/64" 0.5781" (68%) |
| 65% | 14.733 mm 0.5801" | 14.75 mm (64%) | 37/64" 0.5781" (68%) |
| 70% | 14.636 mm 0.5762" | 14.75 mm (64%) | 37/64" 0.5781" (68%) |
| 75% | 14.539 mm 0.5724" | 14.5 mm (77%) | 37/64" 0.5781" (68%) |
| 80% | 14.441 mm 0.5685" | 14.5 mm (77%) | 9/16" 0.5625" (88%) |
About this size
Fine-pitch metric threads are used where you need more strength in thin walls, finer adjustment or better resistance to vibration, for example on hydraulic and automotive parts. The pitch must be written in full (M10 × 1.25); without it, M10 means coarse.
- For stainless steel, duplex and other tough materials, go to about 65% thread: a 14.75 mm drill gives 64%. For mild steel, brass and cast iron the 14.5 mm is fine.
- For a blind hole with 1.5 × D thread engagement (24 mm), drill about 30 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 × 1.5
| 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 × 1.5 thread data
| Designation | M16×1.5 fine |
|---|---|
| Standard | ISO 68-1 basic profile, ISO 261/262 series |
| Pitch | 1.5 mm pitch (16.9 TPI equivalent) |
| Thread angle | 60° |
| Major diameter | 16 mm (0.630") |
| Pitch (effective) diameter | 15.026 mm (0.592") |
| Minor diameter, external | 14.16 mm (0.557") |
| Minor diameter, internal | 14.376 mm (0.566") |
| Thread depth (internal) | 0.812 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:
- 14.25 mm drill → about 90% thread
- 14.5 mm drill → about 77% thread
- 14.75 mm drill → about 64% thread
Other pitches of M16: M16 coarse.
Threads close in size (not interchangeable – the pitch and/or angle differ):
- M16 – 16 mm major, 2 mm pitch (12.7 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 × 1.5 tap?
The tap drill for M16×1.5 fine is 14.5 mm. That’s the standard chart size and gives about 77% of full thread.
What size clearance hole for M16 × 1.5?
For a M16 × 1.5 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 × 1.5?
M16×1.5 fine has a 1.5 mm pitch (16.9 TPI equivalent), a 60° thread angle and a 16 mm major diameter.
Sources: Chart drill: the usual fine-pitch rule, drill = D − P. Percent values 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.
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