# Letter E drill size

A letter E drill is 0.2500 in (6.35 mm). It is the same size as a 1/4 in drill; the nearest metric drills are 6.3 and 6.4 mm, equally close.

## Letter E drill data

- Series: Letter drill
- Decimal: 0.2500 in
- Metric: 6.35 mm (6.3500 mm exact)
- Nearest metric drill: 6.3 mm (−0.050 mm)
- Nearest fractional: 1/4" (0.2500 in)
- Same size as: 1/4"

## Nearest metric drills

| Metric drill | Inch | Difference |
|---|---|---|
| 6.3 mm | 0.2480 | −0.050 mm |
| 6.4 mm | 0.2520 | +0.050 mm |

## Nearby inch drills

| Drill | Series | Inch | mm |
|---|---|---|---|
| #1 | Number | 0.2280 | 5.79 |
| 15/64" | Fractional | 0.2344 | 5.95 |
| Letter D | Letter | 0.2460 | 6.25 |
| 1/4" | Fractional | 0.2500 | 6.35 |
| Letter E | Letter | 0.2500 | 6.35 |
| Letter F | Letter | 0.2570 | 6.53 |
| 17/64" | Fractional | 0.2656 | 6.75 |

## Clearance

| Fastener | Diameter | Clearance | Per side | ISO 273 |
|---|---|---|---|---|
| #10 screw | 0.1900" | 0.0600" | 0.0300" | – |
| #12 screw | 0.2160" | 0.0340" | 0.0170" | – |
| M6 bolt | 6 mm | 0.35 mm | 0.17 mm | Tighter than close fit (6.4 mm) |


## FAQ

**What size is a letter E drill?**
A letter E drill is 0.2500 in, which is 6.35 mm (6.3500 mm exactly).

**What is the metric equivalent of a letter E drill?**
The nearest metric drill is 6.3 mm, 0.050 mm smaller. The other close size is 6.4 mm.

**Which fractional drill is closest to letter E?**
1/4 in (0.2500 in) is the closest, 0.0000 in smaller.

**Is a letter E drill the same as a 1/4 in drill?**
Yes. Both are 0.2500 in (6.35 mm).

**What does a letter E drill clear?**
It clears a M6 bolt with 0.35 mm total clearance (0.17 mm per side); for metric bolts: tighter than close fit.

Source page: https://machinistcharts.com/drill-size/letter-e/
Updated: 2026-10-06
Publisher: MachinistCharts (https://machinistcharts.com)