# Letter J drill size

A letter J drill is 0.2770 in (7.04 mm). It sits between letter I and letter K in the letter series; the nearest metric drill is 7.0 mm.

## Letter J drill data

- Series: Letter drill
- Decimal: 0.2770 in
- Metric: 7.04 mm (7.0358 mm exact)
- Nearest metric drill: 7.0 mm (−0.036 mm)
- Nearest fractional: 9/32" (0.2812 in)

## Nearest metric drills

| Metric drill | Inch | Difference |
|---|---|---|
| 7.0 mm | 0.2756 | −0.036 mm |
| 7.1 mm | 0.2795 | +0.064 mm |

## Nearby inch drills

| Drill | Series | Inch | mm |
|---|---|---|---|
| #1 | Number | 0.2280 | 5.79 |
| 17/64" | Fractional | 0.2656 | 6.75 |
| Letter I | Letter | 0.2720 | 6.91 |
| Letter J | Letter | 0.2770 | 7.04 |
| Letter K | Letter | 0.2810 | 7.14 |
| 9/32" | Fractional | 0.2812 | 7.14 |

## Threads this drill can tap

| Thread | Standard drill | Thread % with this drill |
|---|---|---|
| M8 × 1 | 7 mm | 74 |
| 5/16-24 UNF | I | 66 |
| M8 × 1.25 | 6.8 mm | 59 |

## Clearance

| Fastener | Diameter | Clearance | Per side | ISO 273 |
|---|---|---|---|---|
| #12 screw | 0.2160" | 0.0610" | 0.0305" | – |
| 1/4" bolt | 0.2500" | 0.0270" | 0.0135" | – |


## FAQ

**What size is a letter J drill?**
A letter J drill is 0.2770 in, which is 7.04 mm (7.0358 mm exactly).

**What is the metric equivalent of a letter J drill?**
The nearest metric drill is 7.0 mm, 0.036 mm smaller. The other close size is 7.1 mm.

**What thread can I tap with a letter J drill?**
It leaves about 74 % thread in M8 × 1 and 66 % in 5/16-24 UNF.

**Which fractional drill is closest to letter J?**
9/32 in (0.2812 in) is the closest, 0.0042 in larger.

**What does a letter J drill clear?**
It clears a 1/4" bolt with 0.0270" total clearance (0.0135" per side).

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