---
title: "M8×1.25 tap drill 6.8 mm, clearance 8.4 mm"
description: "M8×1.25: tap drill 6.8 mm, clearance hole 8.4 mm, 13 mm hex. Full thread dimensions, how to identify it, and torque."
url: https://atoneplace.net/fastener/m8-1-25/
site: "At One Place"
---

# M8×1.25 thread

**M8×1.25 tap drill: 6.8 mm**

Clearance hole 8.4 mm · 13 mm hex

M8×1.25 is a coarse metric thread with a 8 mm (0.315") major diameter and 1.25 mm pitch. Tap it with a 6.8 mm drill; drill 8.4 mm to pass a bolt through.

## The numbers

- **Designation:** M8×1.25
- **Major diameter:** 8 mm / 0.315"
- **Minor diameter:** 6.647 mm
- **Pitch:** 1.25 mm pitch
- **Tap drill (75% thread):** 6.8 mm — 6.8 mm
- **Clearance hole (close fit):** 8.4 mm / 0.331"
- **Hex across flats:** 13 mm

## How to measure what you have

1. Measure across the thread crests with calipers. A used M8×1.25 reads a little under 8 mm — the crests are truncated by the standard, then worn and plated, so anything from about 7.6 mm up is consistent with this size.
2. Measure the pitch: put a rule against the threads and count the distance over ten crests, then divide by ten. This one should give 1.25 mm.
3. 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: 21–28 N·m**

15.5–20.7 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

- Bed frame and flat-pack furniture bolts
- Motorcycle engine covers and mirror mounts
- Automotive bracket, cover and heat-shield bolts
- Garden machinery and mower deck hardware

> Nominal minus pitch is 6.75 mm. Every tap drill chart rounds it to the stocked 6.8 mm drill, which is what a tap set contains and what to buy.

## Other threads at this diameter

*Same diameter, different pitch. Forcing the wrong one strips the thread in a turn or two.*

| Thread | Pitch | Tap drill | Clearance |
| --- | --- | --- | --- |
| M8×1 | 1 mm | 7 mm | 8.4 mm |
| M8×0.75 | 0.75 mm | 7.2 mm | 8.4 mm |

## Common questions

### What size drill for an M8×1.25 tap?

6.8 mm (6.8 mm), which gives about 75% thread engagement.

### What clearance hole for M8×1.25?

8.4 mm for a close fit — enough to pass the bolt without slop.

### What spanner fits M8×1.25?

13 mm across the flats on a standard hex head.

## Related pages

- [M8×1](https://atoneplace.net/fastener/m8-1/)
- [M8×0.75](https://atoneplace.net/fastener/m8-0-75/)
- [M6×1](https://atoneplace.net/fastener/m6-1/)
- [M10×1.5](https://atoneplace.net/fastener/m10-1-5/)
- [M6×0.75](https://atoneplace.net/fastener/m6-0-75/)
- [M10×1.25](https://atoneplace.net/fastener/m10-1-25/)
- [M10×1](https://atoneplace.net/fastener/m10-1/)
- [M5×0.8](https://atoneplace.net/fastener/m5-0-8/)
- [M4×0.7](https://atoneplace.net/fastener/m4-0-7/)
- [M12×1.75](https://atoneplace.net/fastener/m12-1-75/)
- [M12×1.5](https://atoneplace.net/fastener/m12-1-5/)
- [M12×1.25](https://atoneplace.net/fastener/m12-1-25/)

## Sources

- Official vendor product documentation — At One Place (/about/)
- Typical range compiled from manufacturer specifications — At One Place (/about/)