#38 drill size
A #38 drill is 0.1015 in (2.58 mm). It is the standard tap drill for #5-40 UNC; the nearest metric drill is 2.6 mm.
#38 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 |
|---|---|---|---|---|
| 2.55 mm | 0.1004" | −0.028 mm | −0.0011" | Smaller |
| 2.6 mm | 0.1024" | +0.022 mm | +0.0009" | 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 #38 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 #38 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 |
|---|---|---|---|---|
| #1 screw | 0.0730" | 0.0285" | 0.0143" | – |
| M2 bolt | 2 mm | 0.58 mm | 0.29 mm | Normal fit (normal 2.4, loose 2.6 mm) |
| #2 screw | 0.0860" | 0.0155" | 0.0078" | – |
| M2.5 bolt | 2.5 mm | 0.08 mm | 0.04 mm | Tighter than close fit (2.7 mm) |
| #3 screw | 0.0990" | 0.0025" | 0.0013" | – |
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 #38 drill?
A #38 drill is 0.1015 in, which is 2.58 mm (2.5781 mm exactly).
What is the metric equivalent of a #38 drill?
The nearest metric drill is 2.6 mm, 0.022 mm larger. The other close size is 2.55 mm.
What tap uses a #38 drill?
A #38 drill is the standard tap drill for #5-40 UNC (about 72 % thread).
Which fractional drill is closest to #38?
3/32 in (0.0938 in) is the closest, 0.0078 in smaller.
What does a #38 drill clear?
It clears a #3 screw with 0.0025" total clearance (0.0013" per side).