33/64" drill size
A 33/64 in drill is 0.5156 in (13.10 mm). It is the standard tap drill for 9/16-18 UNF; the nearest metric drill is 13.1 mm.
33/64" at a glance
Decimal, metric and the nearest sizes in the other series.
- Decimal inch
- 0.5156"
- Millimetres
- 13.10 mm 13.0969
- Nearest metric drill
- 13.1 mm +0.003 mm
- Hole area
- 0.209 in² 134.7 mm²
- Tap drill for
- 9/16-18 UNF
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 |
|---|---|---|---|---|
| 13.0 mm | 0.5118" | −0.097 mm | −0.0038" | Smaller |
| 13.1 mm | 0.5157" | +0.003 mm | +0.0001" | 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 33/64" 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 |
|---|---|---|---|
| 9/16-18 UNF | 33/64 | 65 % | Standard drill |
Clearance for screws and bolts
Bolts and screws a 33/64" 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 |
|---|---|---|---|---|
| M12 bolt | 12 mm | 1.10 mm | 0.55 mm | Close fit (close 13, normal 13.5 mm) |
| 1/2" bolt | 0.5000" | 0.0156" | 0.0078" | – |
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 33/64 in drill?
A 33/64 in drill is 0.5156 in, which is 13.10 mm (13.0969 mm exactly).
What is the metric equivalent of a 33/64 in drill?
The nearest metric drill is 13.1 mm, 0.003 mm larger. The other close size is 13.0 mm.
What tap uses a 33/64 in drill?
A 33/64 in drill is the standard tap drill for 9/16-18 UNF (about 65 % thread).
What does a 33/64 in drill clear?
It clears a 1/2" bolt with 0.0156" total clearance (0.0078" per side).