Letter A drill size
A letter A drill is 0.2340 in (5.94 mm). It is the smallest letter drill on this chart; the nearest metric drill is 5.9 mm.
Letter A at a glance
Decimal, metric and the nearest sizes in the other series.
Nearest metric drills
Metric drills step by 0.05 mm below 3 mm and by 0.1 mm from 3 mm. Difference is metric minus inch size.
| Metric drill | Inch | Difference | In inches | Hole |
|---|---|---|---|---|
| 5.9 mm | 0.2323" | −0.044 mm | −0.0017" | Smaller |
| 6.0 mm | 0.2362" | +0.056 mm | +0.0022" | Larger |
Nearby inch drills
The next size down and up in each inch series, so you can pick a substitute from the drawer.
Threads a Letter A drill can tap
No thread in the tap tables on this site falls between 55 and 85 % thread with this drill, so it is not a useful tap drill for them. Drills this size are mostly used for clearance, pilot and pin holes.
Clearance for screws and bolts
Bolts and screws a Letter A hole clears, with the diametral clearance and the gap each side. Metric sizes are compared with ISO 273.
| Fastener | Diameter | Clearance | Per side | ISO 273, metric only |
|---|---|---|---|---|
| #10 screw | 0.1900" | 0.0440" | 0.0220" | – |
| #12 screw | 0.2160" | 0.0180" | 0.0090" | – |
Inch clearance is the drill size minus the basic major diameter. A drilled hole usually cuts slightly oversize.
Letter drill index
Every size in the series, holes drawn to scale.
Common questions
What size is a letter A drill?
A letter A drill is 0.2340 in, which is 5.94 mm (5.9436 mm exactly).
What is the metric equivalent of a letter A drill?
The nearest metric drill is 5.9 mm, 0.044 mm smaller. The other close size is 6.0 mm.
Which fractional drill is closest to letter A?
15/64 in (0.2344 in) is the closest, 0.0004 in larger.
What does a letter A drill clear?
It clears a #12 screw with 0.0180" total clearance (0.0090" per side).