27/64" drill size
A 27/64 in drill is 0.4219 in (10.72 mm). It is the standard tap drill for 1/2-13 UNC; the nearest metric drill is 10.7 mm.
27/64" at a glance
Decimal, metric and the nearest sizes in the other series.
- Decimal inch
- 0.4219"
- Millimetres
- 10.72 mm 10.7156
- Nearest metric drill
- 10.7 mm −0.016 mm
- Nearest letter drill
- Letter Z 0.4130", −0.0089"
- Hole area
- 0.140 in² 90.2 mm²
- Tap drill for
- 1/2-13 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 |
|---|---|---|---|---|
| 10.7 mm | 0.4213" | −0.016 mm | −0.0006" | Smaller |
| 10.8 mm | 0.4252" | +0.084 mm | +0.0033" | 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 27/64" 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 |
|---|---|---|---|
| 1/2-13 UNC | 27/64 | 78 % | Standard drill |
| M12 × 1.25 | 10.8 mm | 79 % | Soft metals, plastics |
| M12 × 1.5 | 10.5 mm | 66 % | Good in steel |
| M12 × 1.75 | 10.2 mm | 56 % | Hard, tough metals |
Clearance for screws and bolts
Bolts and screws a 27/64" 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 |
|---|---|---|---|---|
| 3/8" bolt | 0.3750" | 0.0469" | 0.0234" | – |
| M10 bolt | 10 mm | 0.72 mm | 0.36 mm | Close fit (close 10.5, normal 11 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 27/64 in drill?
A 27/64 in drill is 0.4219 in, which is 10.72 mm (10.7156 mm exactly).
What is the metric equivalent of a 27/64 in drill?
The nearest metric drill is 10.7 mm, 0.016 mm smaller. The other close size is 10.8 mm.
What tap uses a 27/64 in drill?
A 27/64 in drill is the standard tap drill for 1/2-13 UNC (about 78 % thread).
Which number or letter drill is closest to 27/64 in?
Letter Z (0.4130 in) is the closest, 0.0089 in smaller.
What does a 27/64 in drill clear?
It clears a M10 bolt with 0.72 mm total clearance (0.36 mm per side); for metric bolts: close fit.