# Letter K drill size

A letter K drill is 0.2810 in (7.14 mm). It sits between letter J and letter L in the letter series; the nearest metric drill is 7.1 mm.

## Letter K drill data

- Series: Letter drill
- Decimal: 0.2810 in
- Metric: 7.14 mm (7.1374 mm exact)
- Nearest metric drill: 7.1 mm (−0.037 mm)
- Nearest fractional: 9/32" (0.2812 in)

## Nearest metric drills

| Metric drill | Inch | Difference |
|---|---|---|
| 7.1 mm | 0.2795 | −0.037 mm |
| 7.2 mm | 0.2835 | +0.063 mm |

## Nearby inch drills

| Drill | Series | Inch | mm |
|---|---|---|---|
| #1 | Number | 0.2280 | 5.79 |
| 17/64" | Fractional | 0.2656 | 6.75 |
| Letter J | Letter | 0.2770 | 7.04 |
| Letter K | Letter | 0.2810 | 7.14 |
| 9/32" | Fractional | 0.2812 | 7.14 |
| Letter L | Letter | 0.2900 | 7.37 |

## Threads this drill can tap

| Thread | Standard drill | Thread % with this drill |
|---|---|---|
| M8 × 1 | 7 mm | 66 |
| 5/16-24 UNF | I | 58 |

## Clearance

| Fastener | Diameter | Clearance | Per side | ISO 273 |
|---|---|---|---|---|
| 1/4" bolt | 0.2500" | 0.0310" | 0.0155" | – |


## FAQ

**What size is a letter K drill?**
A letter K drill is 0.2810 in, which is 7.14 mm (7.1374 mm exactly).

**What is the metric equivalent of a letter K drill?**
The nearest metric drill is 7.1 mm, 0.037 mm smaller. The other close size is 7.2 mm.

**What thread can I tap with a letter K drill?**
It leaves about 66 % thread in M8 × 1 and 58 % in 5/16-24 UNF.

**Which fractional drill is closest to letter K?**
9/32 in (0.2812 in) is the closest, 0.0002 in larger.

**What does a letter K drill clear?**
It clears a 1/4" bolt with 0.0310" total clearance (0.0155" per side).

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