---
title: "M2×0.4 tap drill 1.6 mm, clearance 2.2 mm"
description: "M2×0.4: tap drill 1.6 mm, clearance hole 2.2 mm, 4 mm hex. Full thread dimensions, how to identify it, and torque."
url: https://atoneplace.net/fastener/m2-0-4/
site: "At One Place"
---

# M2×0.4 thread

**M2×0.4 tap drill: 1.6 mm**

Clearance hole 2.2 mm · 4 mm hex

M2×0.4 is a coarse metric thread with a 2 mm (0.079") major diameter and 0.4 mm pitch. Tap it with a 1.6 mm drill; drill 2.2 mm to pass a bolt through.

## The numbers

- **Designation:** M2×0.4
- **Major diameter:** 2 mm / 0.079"
- **Minor diameter:** 1.567 mm
- **Pitch:** 0.4 mm pitch
- **Tap drill (75% thread):** 1.6 mm — 1.6 mm
- **Clearance hole (close fit):** 2.2 mm / 0.087"
- **Hex across flats:** 4 mm

## How to measure what you have

1. Measure across the thread crests with calipers. A used M2×0.4 reads a little under 2 mm — the crests are truncated by the standard, then worn and plated, so anything from about 1.6 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 0.4 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

No torque figure is given for this size. Small and fine threads like this are generally not supplied to a strength grade, and in most assemblies the tapped material strips before the fastener yields — so a published bolt torque would be the wrong limit to work to. Tighten to snug plus a small turn, or use the figure the manufacturer of the part specifies.

## Where this size turns up

- M.2 SSD retaining screw on desktop and laptop motherboards
- Flight-controller and ESC mounting on small drones
- Camera and lens body screws

## Common questions

### What size drill for an M2×0.4 tap?

1.6 mm (1.6 mm), which gives about 75% thread engagement.

### What clearance hole for M2×0.4?

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

### What spanner fits M2×0.4?

4 mm across the flats on a standard hex head.

## Related pages

- [M1.6×0.35](https://atoneplace.net/fastener/m1-6-0-35/)
- [M2.5×0.45](https://atoneplace.net/fastener/m2-5-0-45/)
- [M3×0.5](https://atoneplace.net/fastener/m3-0-5/)
- [M3.5×0.6](https://atoneplace.net/fastener/m3-5-0-6/)
- [M4×0.7](https://atoneplace.net/fastener/m4-0-7/)
- [M5×0.8](https://atoneplace.net/fastener/m5-0-8/)
- [M6×1](https://atoneplace.net/fastener/m6-1/)
- [M6×0.75](https://atoneplace.net/fastener/m6-0-75/)
- [M8×1.25](https://atoneplace.net/fastener/m8-1-25/)
- [M8×1](https://atoneplace.net/fastener/m8-1/)

## Sources

- Official vendor product documentation — At One Place (/about/)