21/32" drill size
A 21/32 in drill is 0.6562 in (16.67 mm). It is the standard tap drill for 3/4-10 UNC; the nearest metric drill is 16.7 mm.
21/32" at a glance
Decimal, metric and the nearest sizes in the other series.
- Decimal inch
- 0.6562"
- Millimetres
- 16.67 mm 16.6687
- Nearest metric drill
- 16.7 mm +0.031 mm
- Hole area
- 0.338 in² 218.2 mm²
- Tap drill for
- 3/4-10 UNC
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 |
|---|---|---|---|---|
| 16.6 mm | 0.6535" | −0.069 mm | −0.0027" | Smaller |
| 16.7 mm | 0.6575" | +0.031 mm | +0.0012" | 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 21/32" 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 |
|---|---|---|---|
| 3/4-10 UNC | 21/32 | 72 % | Standard drill |
| M18 × 1.5 | 16.5 mm | 68 % | Good in steel |
Clearance for screws and bolts
Bolts and screws a 21/32" 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 |
|---|---|---|---|---|
| 5/8" bolt | 0.6250" | 0.0312" | 0.0156" | – |
| M16 bolt | 16 mm | 0.67 mm | 0.33 mm | Tighter than close fit (17 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 21/32 in drill?
A 21/32 in drill is 0.6562 in, which is 16.67 mm (16.6687 mm exactly).
What is the metric equivalent of a 21/32 in drill?
The nearest metric drill is 16.7 mm, 0.031 mm larger. The other close size is 16.6 mm.
What tap uses a 21/32 in drill?
A 21/32 in drill is the standard tap drill for 3/4-10 UNC (about 72 % thread).
What does a 21/32 in drill clear?
It clears a M16 bolt with 0.67 mm total clearance (0.33 mm per side); for metric bolts: tighter than close fit.