M33×3.5 thread
M33×3.5 tap drill
29.5 mm
Clearance hole 34 mm · 50 mm hex
M33×3.5 is a coarse metric thread with a 33 mm (1.299") major diameter and 3.5 mm pitch. Tap it with a 29.5 mm drill; drill 34 mm to pass a bolt through.
The numbers
- Designation
- M33×3.5
- Major diameter
- 33 mm / 1.299"
- Minor diameter
- 29.211 mm
- Pitch
- 3.5 mm pitch
- Tap drill (75% thread)
- 29.5 mm — 29.5 mm
- Clearance hole (close fit)
- 34 mm / 1.339"
- Hex across flats
- 50 mm
How to measure what you have
- Measure across the thread crests with calipers. A used M33×3.5 reads a little under 33 mm — the crests are truncated by the standard, then worn and plated, so anything from about 32.6 mm up is consistent with this size.
- Measure the pitch: put a rule against the threads and count the distance over ten crests, then divide by ten. This one should give 3.5 mm.
- A thread pitch gauge settles it in seconds and costs very little. Guessing between a coarse and a fine thread of the same diameter is the usual way a thread gets stripped.
Tightening torque
Typical torque
1700–2250 N·m
1254.1–1659.8 lb·ft
Plain steel property class 8.8 or SAE grade 5, dry threads, tightened to about 65% of yield. Lubricated threads reach the same preload at 20-30% less torque. Where the manufacturer publishes a figure — spark plugs, wheel nuts, cylinder heads — use theirs.
Where this size turns up
- Heavy flange bolting
- Large press and forging equipment
- Marine and offshore structural connections
Common questions
- What size drill for an M33×3.5 tap?
- 29.5 mm (29.5 mm), which gives about 75% thread engagement.
- What clearance hole for M33×3.5?
- 34 mm for a close fit — enough to pass the bolt without slop.
- What spanner fits M33×3.5?
- 50 mm across the flats on a standard hex head.
Related pages
Sources
- Official vendor product documentation — At One Place
- Typical range compiled from manufacturer specifications — At One Place