---
title: "M1.6×0.35 tap drill 1.25 mm, clearance 1.7 mm"
description: "M1.6×0.35: tap drill 1.25 mm, clearance hole 1.7 mm, 3.2 mm hex. Full thread dimensions, how to identify it, and torque."
url: https://atoneplace.net/fastener/m1-6-0-35/
site: "At One Place"
---

# M1.6×0.35 thread

**M1.6×0.35 tap drill: 1.25 mm**

Clearance hole 1.7 mm · 3.2 mm hex

M1.6×0.35 is a coarse metric thread with a 1.6 mm (0.063") major diameter and 0.35 mm pitch. Tap it with a 1.25 mm drill; drill 1.7 mm to pass a bolt through.

## The numbers

- **Designation:** M1.6×0.35
- **Major diameter:** 1.6 mm / 0.063"
- **Minor diameter:** 1.221 mm
- **Pitch:** 0.35 mm pitch
- **Tap drill (75% thread):** 1.25 mm — 1.25 mm
- **Clearance hole (close fit):** 1.7 mm / 0.067"
- **Hex across flats:** 3.2 mm

## How to measure what you have

1. Measure across the thread crests with calipers. A used M1.6×0.35 reads a little under 1.6 mm — the crests are truncated by the standard, then worn and plated, so anything from about 1.2 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 0.35 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

- Spectacle hinge and temple screws
- Terminal screws in small relays and connectors
- Watch case backs and strap bars

## Common questions

### What size drill for an M1.6×0.35 tap?

1.25 mm (1.25 mm), which gives about 75% thread engagement.

### What clearance hole for M1.6×0.35?

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

### What spanner fits M1.6×0.35?

3.2 mm across the flats on a standard hex head.

## Related pages

- [M2×0.4](https://atoneplace.net/fastener/m2-0-4/)
- [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/)