M14×1.5 thread
M14×1.5 tap drill
12.5 mm
Clearance hole 15 mm · 21 mm hex
M14×1.5 is a fine metric thread with a 14 mm (0.551") major diameter and 1.5 mm pitch. Tap it with a 12.5 mm drill; drill 15 mm to pass a bolt through.
The numbers
- Designation
- M14×1.5
- Major diameter
- 14 mm / 0.551"
- Minor diameter
- 12.376 mm
- Pitch
- 1.5 mm pitch
- Tap drill (75% thread)
- 12.5 mm — 12.5 mm
- Clearance hole (close fit)
- 15 mm / 0.591"
- Hex across flats
- 21 mm
How to measure what you have
- Measure across the thread crests with calipers. A used M14×1.5 reads a little under 14 mm — the crests are truncated by the standard, then worn and plated, so anything from about 13.6 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 1.5 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
124–167 N·m
91.5–123.2 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
- Wheel bolts on Volkswagen, Audi, BMW and Mercedes
- Larger oil drain and sump plugs
- Hydraulic adaptor threads
Other threads at this diameter
| Thread | Pitch | Tap drill | Clearance |
|---|---|---|---|
| M14×2 | 2 mm | 12 mm | 15 mm |
| M14×1.25 | 1.25 mm | 12.8 mm | 15 mm |
Common questions
- What size drill for an M14×1.5 tap?
- 12.5 mm (12.5 mm), which gives about 75% thread engagement.
- What clearance hole for M14×1.5?
- 15 mm for a close fit — enough to pass the bolt without slop.
- What spanner fits M14×1.5?
- 21 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