51/64" drill size
A 51/64 in drill is 0.7969 in (20.24 mm). It sits between 25/32 in and 13/16 in in the fractional series; the nearest metric drill is 20.2 mm.
51/64" 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 |
|---|---|---|---|---|
| 20.2 mm | 0.7953" | −0.041 mm | −0.0016" | Smaller |
| 20.3 mm | 0.7992" | +0.059 mm | +0.0023" | 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 51/64" 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 |
|---|---|---|---|
| 7/8-14 UNF | 13/16 | 84 % | Soft metals, plastics |
Clearance for screws and bolts
Bolts and screws a 51/64" 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 |
|---|---|---|---|---|
| M18 bolt | 18 mm | 2.24 mm | 1.12 mm | Normal fit (normal 20, loose 21 mm) |
| 3/4" bolt | 0.7500" | 0.0469" | 0.0234" | – |
| M20 bolt | 20 mm | 0.24 mm | 0.12 mm | Tighter than close fit (21 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 51/64 in drill?
A 51/64 in drill is 0.7969 in, which is 20.24 mm (20.2406 mm exactly).
What is the metric equivalent of a 51/64 in drill?
The nearest metric drill is 20.2 mm, 0.041 mm smaller. The other close size is 20.3 mm.
What thread can I tap with a 51/64 in drill?
It leaves about 84 % thread in 7/8-14 UNF.
What does a 51/64 in drill clear?
It clears a M20 bolt with 0.24 mm total clearance (0.12 mm per side); for metric bolts: tighter than close fit.