M5×0.8 thread
M5×0.8 tap drill
4.2 mm
Clearance hole 5.3 mm · 8 mm hex
M5×0.8 is a coarse metric thread with a 5 mm (0.197") major diameter and 0.8 mm pitch. Tap it with a 4.2 mm drill; drill 5.3 mm to pass a bolt through.
The numbers
- Designation
- M5×0.8
- Major diameter
- 5 mm / 0.197"
- Minor diameter
- 4.134 mm
- Pitch
- 0.8 mm pitch
- Tap drill (75% thread)
- 4.2 mm — 4.2 mm
- Clearance hole (close fit)
- 5.3 mm / 0.209"
- Hex across flats
- 8 mm
How to measure what you have
- Measure across the thread crests with calipers. A used M5×0.8 reads a little under 5 mm — the crests are truncated by the standard, then worn and plated, so anything from about 4.6 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 0.8 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
5–6.8 N·m
3.7–5.0 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
- Bicycle bottle cage bosses
- Bicycle disc rotor bolts and stem face-plate bolts
- T-slot nuts in 2020 aluminium extrusion
- VESA 200×200 monitor and TV mounts
Common questions
- What size drill for an M5×0.8 tap?
- 4.2 mm (4.2 mm), which gives about 75% thread engagement.
- What clearance hole for M5×0.8?
- 5.3 mm for a close fit — enough to pass the bolt without slop.
- What spanner fits M5×0.8?
- 8 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