55/64" drill size
A 55/64 in drill is 0.8594 in (21.83 mm). It sits between 27/32 in and 7/8 in in the fractional series; the nearest metric drill is 21.8 mm.
55/64" 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 |
|---|---|---|---|---|
| 21.8 mm | 0.8583" | −0.028 mm | −0.0011" | Smaller |
| 21.9 mm | 0.8622" | +0.072 mm | +0.0028" | 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 55/64" 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).
Clearance for screws and bolts
Bolts and screws a 55/64" 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 |
|---|---|---|---|---|
| M20 bolt | 20 mm | 1.83 mm | 0.91 mm | Close fit (close 21, normal 22 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 55/64 in drill?
A 55/64 in drill is 0.8594 in, which is 21.83 mm (21.8281 mm exactly).
What is the metric equivalent of a 55/64 in drill?
The nearest metric drill is 21.8 mm, 0.028 mm smaller. The other close size is 21.9 mm.
What thread can I tap with a 55/64 in drill?
It leaves about 84 % thread in M24 × 2 and 56 % in M24 × 3.
What does a 55/64 in drill clear?
It clears a M20 bolt with 1.83 mm total clearance (0.91 mm per side); for metric bolts: close fit.