#27 drill size
A #27 drill is 0.1440 in (3.66 mm). It sits between #28 and #26 in the number series; the nearest metric drill is 3.7 mm.
#27 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 |
|---|---|---|---|---|
| 3.6 mm | 0.1417" | −0.058 mm | −0.0023" | Smaller |
| 3.7 mm | 0.1457" | +0.042 mm | +0.0017" | 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 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 |
|---|---|---|---|
| #10-24 UNC | #25 | 85 % | Soft metals, plastics |
| #8-36 UNF | #29 | 55 % | Hard, tough metals |
Clearance for screws and bolts
Bolts and screws a #27 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 |
|---|---|---|---|---|
| #2 screw | 0.0860" | 0.0580" | 0.0290" | – |
| #3 screw | 0.0990" | 0.0450" | 0.0225" | – |
| #4 screw | 0.1120" | 0.0320" | 0.0160" | – |
| #5 screw | 0.1250" | 0.0190" | 0.0095" | – |
| M3.5 bolt | 3.5 mm | 0.16 mm | 0.08 mm | Tighter than close fit (3.7 mm) |
| #6 screw | 0.1380" | 0.0060" | 0.0030" | – |
Inch clearance is the drill size minus the basic major diameter. A drilled hole usually cuts slightly oversize.
Number drill index
Every size in the series, holes drawn to scale.
Common questions
What size is a #27 drill?
A #27 drill is 0.1440 in, which is 3.66 mm (3.6576 mm exactly).
What is the metric equivalent of a #27 drill?
The nearest metric drill is 3.7 mm, 0.042 mm larger. The other close size is 3.6 mm.
What thread can I tap with a #27 drill?
It leaves about 85 % thread in #10-24 UNC and 55 % in #8-36 UNF.
Which fractional drill is closest to #27?
9/64 in (0.1406 in) is the closest, 0.0034 in smaller.
What does a #27 drill clear?
It clears a #6 screw with 0.0060" total clearance (0.0030" per side).