# Letter D drill size

A letter D drill is 0.2460 in (6.25 mm). It sits between letter C and letter E in the letter series; the nearest metric drill is 6.2 mm.

## Letter D drill data

- Series: Letter drill
- Decimal: 0.2460 in
- Metric: 6.25 mm (6.2484 mm exact)
- Nearest metric drill: 6.2 mm (−0.048 mm)
- Nearest fractional: 1/4" (0.2500 in)

## Nearest metric drills

| Metric drill | Inch | Difference |
|---|---|---|
| 6.2 mm | 0.2441 | −0.048 mm |
| 6.3 mm | 0.2480 | +0.052 mm |

## Nearby inch drills

| Drill | Series | Inch | mm |
|---|---|---|---|
| #1 | Number | 0.2280 | 5.79 |
| 15/64" | Fractional | 0.2344 | 5.95 |
| Letter C | Letter | 0.2420 | 6.15 |
| Letter D | Letter | 0.2460 | 6.25 |
| 1/4" | Fractional | 0.2500 | 6.35 |
| Letter E | Letter | 0.2500 | 6.35 |

## Clearance

| Fastener | Diameter | Clearance | Per side | ISO 273 |
|---|---|---|---|---|
| #10 screw | 0.1900" | 0.0560" | 0.0280" | – |
| #12 screw | 0.2160" | 0.0300" | 0.0150" | – |
| M6 bolt | 6 mm | 0.25 mm | 0.12 mm | Tighter than close fit (6.4 mm) |


## FAQ

**What size is a letter D drill?**
A letter D drill is 0.2460 in, which is 6.25 mm (6.2484 mm exactly).

**What is the metric equivalent of a letter D drill?**
The nearest metric drill is 6.2 mm, 0.048 mm smaller. The other close size is 6.3 mm.

**Which fractional drill is closest to letter D?**
1/4 in (0.2500 in) is the closest, 0.0040 in larger.

**What does a letter D drill clear?**
It clears a M6 bolt with 0.25 mm total clearance (0.12 mm per side); for metric bolts: tighter than close fit.

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