1/2" drill size
A 1/2 in drill is 0.5000 in (12.70 mm). It sits between 31/64 in and 33/64 in in the fractional series; the nearest metric drill is 12.7 mm.
1/2" 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 |
|---|---|---|---|---|
| 12.6 mm | 0.4961" | −0.100 mm | −0.0039" | Smaller |
| 12.7 mm | 0.5000" | 0 mm | 0" | Same size |
Nearby inch drills
The next size down and up in each inch series, so you can pick a substitute from the drawer.
Threads a 1/2" drill can tap
Threads from the tap tables on this site that this drill can tap, with the thread percentage it leaves (55–85 % shown).
| Thread | Standard drill | Thread with this drill | Suits |
|---|---|---|---|
| M14 × 1.5 | 12.5 mm | 67 % | Good in steel |
| 9/16-12 UNC | 31/64 | 58 % | Hard, tough metals |
Clearance for screws and bolts
Bolts and screws a 1/2" 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 |
|---|---|---|---|---|
| 7/16" bolt | 0.4375" | 0.0625" | 0.0312" | – |
| M12 bolt | 12 mm | 0.70 mm | 0.35 mm | Tighter than close fit (13 mm) |
Inch clearance is the drill size minus the basic major diameter. A drilled hole usually cuts slightly oversize.
Fractional drill index
Every size in the series, holes drawn to scale.
Common questions
What size is a 1/2 in drill?
A 1/2 in drill is 0.5000 in, which is 12.70 mm (12.7000 mm exactly).
What is the metric equivalent of a 1/2 in drill?
The nearest metric drill is 12.7 mm, 0.000 mm smaller. The other close size is 12.6 mm.
What thread can I tap with a 1/2 in drill?
It leaves about 67 % thread in M14 × 1.5 and 58 % in 9/16-12 UNC.
What does a 1/2 in drill clear?
It clears a M12 bolt with 0.70 mm total clearance (0.35 mm per side); for metric bolts: tighter than close fit.