---
title: "M3×0.5 tap drill 2.5 mm, clearance 3.2 mm"
description: "M3×0.5: tap drill 2.5 mm, clearance hole 3.2 mm, 5.5 mm hex. Full thread dimensions, how to identify it, and torque."
url: https://atoneplace.net/fastener/m3-0-5/
site: "At One Place"
---

# M3×0.5 thread

**M3×0.5 tap drill: 2.5 mm**

Clearance hole 3.2 mm · 5.5 mm hex

M3×0.5 is a coarse metric thread with a 3 mm (0.118") major diameter and 0.5 mm pitch. Tap it with a 2.5 mm drill; drill 3.2 mm to pass a bolt through.

## The numbers

- **Designation:** M3×0.5
- **Major diameter:** 3 mm / 0.118"
- **Minor diameter:** 2.459 mm
- **Pitch:** 0.5 mm pitch
- **Tap drill (75% thread):** 2.5 mm — 2.5 mm
- **Clearance hole (close fit):** 3.2 mm / 0.126"
- **Hex across flats:** 5.5 mm

## How to measure what you have

1. Measure across the thread crests with calipers. A used M3×0.5 reads a little under 3 mm — the crests are truncated by the standard, then worn and plated, so anything from about 2.6 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 0.5 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: 1.1–1.5 N·m**

0.8–1.1 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

- 2.5-inch SATA drive and SSD mounting screws
- 3D printer hot-end, carriage and bed screws
- DIN-rail terminal blocks
- Quadcopter frame and motor screws

## Common questions

### What size drill for an M3×0.5 tap?

2.5 mm (2.5 mm), which gives about 75% thread engagement.

### What clearance hole for M3×0.5?

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

### What spanner fits M3×0.5?

5.5 mm across the flats on a standard hex head.

## Related pages

- [M2.5×0.45](https://atoneplace.net/fastener/m2-5-0-45/)
- [M3.5×0.6](https://atoneplace.net/fastener/m3-5-0-6/)
- [M2×0.4](https://atoneplace.net/fastener/m2-0-4/)
- [M4×0.7](https://atoneplace.net/fastener/m4-0-7/)
- [M1.6×0.35](https://atoneplace.net/fastener/m1-6-0-35/)
- [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/)
- Typical range compiled from manufacturer specifications — At One Place (/about/)