#43 drill bit size
0.089 in
2.26 mm · number drill · tapping drill for 4-40
| Inches | 0.089 in |
| Millimetres | 2.26 mm |
| Nearest metric drill | 2.3 mm |
| System | Number (#1 to #60) |
| Taps | 4-40 |
What #43 means
A bit marked #43 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 #43:
| System | Nearest size | Difference |
|---|---|---|
| letter | A — 0.234 in | 0.145 in larger |
| fractional | 3/32" — 0.0938 in | 0.0048 in larger |
| metric | 2.3 mm | 0.039 mm larger |
The closest substitute is 0.0048 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 #43 is for
#43 is the standard tapping drill for 4-40 at 75% thread engagement. That is not a coincidence of the tables: the theoretical figure for 4-40 works out at 0.0876 inches, and #43 at 0.089 is the nearest drill that exists.
What gets drilled at 0.089 inches
This is circuit-board and small-pin range — component leads, header pins, the holes a hobbyist drills in perfboard. It is also where the smallest machine-screw taps live, so a drill here is as likely to be preparing a thread as clearing a wire.
Either side of it
| Drill | Inches | Millimetres |
|---|---|---|
| #46 | 0.081 in | 2.06 mm |
| #45 | 0.082 in | 2.08 mm |
| #44 | 0.086 in | 2.18 mm |
| #43 | 0.089 in | 2.26 mm |
| #42 | 0.0935 in | 2.37 mm |
| 3/32" | 0.0938 in | 2.38 mm |
| #41 | 0.096 in | 2.44 mm |
Frequently asked questions
What size is a #43 drill bit?
0.089 inches, which is 2.26 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 #43 drill bit in mm?
2.26 mm. A metric index will offer 2.3 mm as the nearest stocked size, which is 0.039 mm larger — enough to matter when tapping and not enough to matter for a clearance hole.
What tap does a #43 drill bit go with?
4-40 at the standard 75% thread. That thread comes out at a theoretical diameter this drill is the nearest stocked size to.
What is the next size up from #43?
#42 at 0.0935 inches — 0.0045 inches larger. Below it is #44 at 0.086.
Other sizes
- #42 drill bit — 0.0935 in, 2.37 mm
- 3/32" drill bit — 0.0938 in, 2.38 mm
- #41 drill bit — 0.096 in, 2.44 mm
- #40 drill bit — 0.098 in, 2.49 mm
- #39 drill bit — 0.0995 in, 2.53 mm
- #38 drill bit — 0.1015 in, 2.58 mm
- #37 drill bit — 0.104 in, 2.64 mm
- #36 drill bit — 0.1065 in, 2.71 mm