M14 tap drill size
The tap drill for M14×2 is 12 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% | 12.441 mm 0.4898" | 12.4 mm (62%) | 31/64" 0.4844" (65%) |
| 65% | 12.311 mm 0.4847" | 12.3 mm (65%) | 31/64" 0.4844" (65%) |
| 70% | 12.181 mm 0.4796" | 12.2 mm (69%) | 31/64" 0.4844" (65%) |
| 75% | 12.051 mm 0.4745" | 12.1 mm (73%) | 15/32" 0.4688" (81%) |
| 80% | 11.922 mm 0.4694" | 11.9 mm (81%) | 15/32" 0.4688" (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 12.3 mm drill gives 65%. For mild steel, brass and cast iron the 12 mm is fine.
- For a blind hole with 1.5 × D thread engagement (21 mm), drill about 29 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 M14
| Fit | Drill |
|---|---|
| Close | 15 mm (0.591") |
| Medium (normal) | 15.5 mm (0.610") |
| Free (loose) | 16.5 mm (0.650") |
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.
M14 thread data
| Designation | M14×2 |
|---|---|
| Standard | ISO 68-1 basic profile, ISO 261/262 series |
| Pitch | 2 mm pitch (12.7 TPI equivalent) |
| Thread angle | 60° |
| Major diameter | 14 mm (0.551") |
| Pitch (effective) diameter | 12.701 mm (0.500") |
| Minor diameter, external | 11.546 mm (0.455") |
| Minor diameter, internal | 11.835 mm (0.466") |
| Thread depth (internal) | 1.083 mm |
Basic sizes. Real screws are slightly under and real nuts slightly over these values because of tolerance classes.
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Nearest alternatives
If you don’t have the right drill, these give:
- 12 mm drill → about 77% thread
- 12.1 mm drill → about 73% thread
- 12.2 mm drill → about 69% thread
Other pitches of M14: M14 × 1.5.
Threads close in size (not interchangeable – the pitch and/or angle differ):
- M14 × 1.5 – 14 mm major, 1.5 mm pitch (16.9 TPI equivalent)
- 9/16" UNC – 14.29 mm major, 12 TPI (2.117 mm pitch)
- 9/16" UNF – 14.29 mm major, 18 TPI (1.411 mm pitch)
- 9/16" BSW – 14.29 mm major, 12 TPI (2.117 mm pitch)
- 9/16" BSF – 14.29 mm major, 16 TPI (1.587 mm pitch)
Questions
What size drill for a M14 tap?
The tap drill for M14×2 is 12 mm. That’s the standard chart size and gives about 77% of full thread.
What size clearance hole for M14?
For a M14 screw or bolt, drill 15 mm for a close fit, 15.5 mm for a medium (normal) fit or 16.5 mm for a free fit. These are the ISO 273 fine, medium and coarse sizes.
What is the pitch of M14?
M14×2 has a 2 mm pitch (12.7 TPI equivalent), a 60° thread angle and a 14 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.
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