M5 tap drill size
The tap drill for M5×0.8 is 4.2 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% | 4.376 mm 0.1723" | 4.4 mm (58%) | 11/64" 0.1719" (61%) |
| 65% | 4.325 mm 0.1703" | 4.3 mm (67%) | #18 0.1695" (67%) |
| 70% | 4.273 mm 0.1682" | 4.3 mm (67%) | #18 0.1695" (67%) |
| 75% | 4.221 mm 0.1662" | 4.2 mm (77%) | #19 0.1660" (75%) |
| 80% | 4.169 mm 0.1641" | 4.2 mm (77%) | #19 0.1660" (75%) |
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 4.3 mm drill gives 67%. For mild steel, brass and cast iron the 4.2 mm is fine.
- For a blind hole with 1.5 × D thread engagement (7.5 mm), drill about 10.7 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 M5
| Fit | Drill |
|---|---|
| Close | 5.3 mm (0.209") |
| Medium (normal) | 5.5 mm (0.217") |
| Free (loose) | 5.8 mm (0.228") |
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.
M5 thread data
| Designation | M5×0.8 |
|---|---|
| Standard | ISO 68-1 basic profile, ISO 261/262 series |
| Pitch | 0.8 mm pitch (31.7 TPI equivalent) |
| Thread angle | 60° |
| Major diameter | 5 mm (0.197") |
| Pitch (effective) diameter | 4.48 mm (0.176") |
| Minor diameter, external | 4.019 mm (0.158") |
| Minor diameter, internal | 4.134 mm (0.163") |
| Thread depth (internal) | 0.433 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:
- 4.1 mm drill → about 87% thread
- 4.2 mm drill → about 77% thread
- 4.3 mm drill → about 67% thread
Threads close in size (not interchangeable – the pitch and/or angle differ):
- #10 UNC – 4.83 mm major, 24 TPI (1.058 mm pitch)
- #10 UNF – 4.83 mm major, 32 TPI (0.794 mm pitch)
- 3/16" BSW – 4.76 mm major, 24 TPI (1.058 mm pitch)
- 3/16" BSF – 4.76 mm major, 32 TPI (0.794 mm pitch)
- 1BA – 5.3 mm major, 0.9 mm pitch (28.2 TPI equivalent)
Questions
What size drill for a M5 tap?
The tap drill for M5×0.8 is 4.2 mm. That’s the standard chart size and gives about 77% of full thread.
What size clearance hole for M5?
For a M5 screw or bolt, drill 5.3 mm for a close fit, 5.5 mm for a medium (normal) fit or 5.8 mm for a free fit. These are the ISO 273 fine, medium and coarse sizes.
What is the pitch of M5?
M5×0.8 has a 0.8 mm pitch (31.7 TPI equivalent), a 60° thread angle and a 5 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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