#58 drill bit size
0.042 in
1.07 mm · number drill
| Inches | 0.042 in |
| Millimetres | 1.07 mm |
| Nearest metric drill | 1.1 mm |
| System | Number (#1 to #60) |
What #58 means
A bit marked #58 is a number drill, and the number is an index rather than a measurement — the higher the number, the smaller the bit. #1 is 0.228 inches and #60 is 0.04. That is the opposite of the fractional sizes stamped on a home set, which is why a number drill and a fraction of similar appearance can be very different holes.
The same hole in the other systems
Three drill systems overlap across this range and a workshop rarely has all three. The nearest bit of each other kind to #58:
| System | Nearest size | Difference |
|---|---|---|
| letter | A — 0.234 in | 0.192 in larger |
| fractional | 3/64" — 0.0469 in | 0.0049 in larger |
| metric | 1.1 mm | 0.033 mm larger |
The closest substitute is 0.0049 inches away. For a clearance hole that is nothing; for a tapping hole it moves the thread engagement by several per cent, which is the difference between an easy tap and a broken one.
What gets drilled at 0.042 inches
Under fifty thousandths of an inch, a drill is watchmaker and model-maker territory: pinning small parts, clearing wire in an instrument, opening a jet. Bits this fine snap if the work moves at all, which is why they are used in a press or a pin vice rather than a hand drill.
Either side of it
| Drill | Inches | Millimetres |
|---|---|---|
| 1/32" | 0.0313 in | 0.79 mm |
| #60 | 0.04 in | 1.02 mm |
| #59 | 0.041 in | 1.04 mm |
| #58 | 0.042 in | 1.07 mm |
| #57 | 0.043 in | 1.09 mm |
| #56 | 0.0465 in | 1.18 mm |
| 3/64" | 0.0469 in | 1.19 mm |
Frequently asked questions
What size is a #58 drill bit?
0.042 inches, which is 1.07 mm. Number drills run from #1 at 0.228 inches down to #60 at 0.04, getting smaller as the number rises — the opposite of what most people expect the first time.
What is a #58 drill bit in mm?
1.07 mm. A metric index will offer 1.1 mm as the nearest stocked size, which is 0.033 mm larger — enough to matter when tapping and not enough to matter for a clearance hole.
Is #58 a tapping drill size?
Not for any of the unified threads on this site. It sits between the sizes the standard taps call for, so it is a clearance or pilot drill rather than a tapping one.
What is the next size up from #58?
#57 at 0.043 inches — 0.001 inches larger. Below it is #59 at 0.041.
Other sizes
- #57 drill bit — 0.043 in, 1.09 mm
- #56 drill bit — 0.0465 in, 1.18 mm
- 3/64" drill bit — 0.0469 in, 1.19 mm
- #55 drill bit — 0.052 in, 1.32 mm
- #54 drill bit — 0.055 in, 1.4 mm
- #53 drill bit — 0.0595 in, 1.51 mm
- 1/16" drill bit — 0.0625 in, 1.59 mm
- #52 drill bit — 0.0635 in, 1.61 mm