M48 tap drill size
The tap drill for M48×5 is 43 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% | 44.103 mm 1.7363" | 44 mm (62%) | 1-47/64" 1.7344" (61%) |
| 65% | 43.778 mm 1.7235" | 44 mm (62%) | 1-23/32" 1.7188" (67%) |
| 70% | 43.453 mm 1.7108" | 43.5 mm (69%) | 1-45/64" 1.7031" (73%) |
| 75% | 43.129 mm 1.6980" | 43 mm (77%) | 1-45/64" 1.7031" (73%) |
| 80% | 42.804 mm 1.6852" | 43 mm (77%) | 1-11/16" 1.6875" (79%) |
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 44 mm drill gives 62%. For mild steel, brass and cast iron the 43 mm is fine.
- At this size many people bore the hole and screwcut the thread on the lathe instead of using a hand tap. See the thread calculator for depths and the infeed.
- For a blind hole with 1.5 × D thread engagement (72 mm), drill about 92 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 M48
| Fit | Drill |
|---|---|
| Close | 50 mm (1.969") |
| Medium (normal) | 52 mm (2.047") |
| Free (loose) | 56 mm (2.205") |
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.
M48 thread data
| Designation | M48×5 |
|---|---|
| Standard | ISO 68-1 basic profile, ISO 261/262 series |
| Pitch | 5 mm pitch (5.1 TPI equivalent) |
| Thread angle | 60° |
| Major diameter | 48 mm (1.890") |
| Pitch (effective) diameter | 44.752 mm (1.762") |
| Minor diameter, external | 41.866 mm (1.648") |
| Minor diameter, internal | 42.587 mm (1.677") |
| Thread depth (internal) | 2.706 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:
- 42.5 mm drill → about 85% thread
- 43 mm drill → about 77% thread
- 43.5 mm drill → about 69% thread
Questions
What size drill for a M48 tap?
The tap drill for M48×5 is 43 mm. That’s the standard chart size and gives about 77% of full thread.
What size clearance hole for M48?
For a M48 screw or bolt, drill 50 mm for a close fit, 52 mm for a medium (normal) fit or 56 mm for a free fit. These are the ISO 273 fine, medium and coarse sizes.
What is the pitch of M48?
M48×5 has a 5 mm pitch (5.1 TPI equivalent), a 60° thread angle and a 48 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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