#17 drill bit size
0.173 in
4.39 mm · number drill
| Inches | 0.173 in |
| Millimetres | 4.39 mm |
| Nearest metric drill | 4.4 mm |
| System | Number (#1 to #60) |
What #17 means
A bit marked #17 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 #17:
| System | Nearest size | Difference |
|---|---|---|
| letter | A — 0.234 in | 0.061 in larger |
| fractional | 11/64" — 0.1719 in | 0.0011 in smaller |
| metric | 4.4 mm | 0.006 mm larger |
One of those is within three thousandths of an inch, which is inside the tolerance of most hand-held work — substitute it and nobody will know.
What gets drilled at 0.173 inches
The busiest part of the number series. Tapping drills for machine screws from #4 to #12 sit in here, along with pilot holes for wood screws and clearance for small pins. If a number drill in a workshop is worn out, it is usually one of these.
Either side of it
| Drill | Inches | Millimetres |
|---|---|---|
| #19 | 0.166 in | 4.22 mm |
| #18 | 0.1695 in | 4.31 mm |
| 11/64" | 0.1719 in | 4.37 mm |
| #17 | 0.173 in | 4.39 mm |
| #16 | 0.177 in | 4.5 mm |
| #15 | 0.18 in | 4.57 mm |
| #14 | 0.182 in | 4.62 mm |
Frequently asked questions
What size is a #17 drill bit?
0.173 inches, which is 4.39 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 #17 drill bit in mm?
4.39 mm. A metric index will offer 4.4 mm as the nearest stocked size, which is near enough identical.
Is #17 a tapping drill size?
Not for any of the unified threads on this site. The next size up, #16, is the tapping drill for 12-24.
What is the next size up from #17?
#16 at 0.177 inches — 0.004 inches larger. Below it is 11/64" at 0.1719.
Other sizes
- #16 drill bit — 0.177 in, 4.5 mm
- #15 drill bit — 0.18 in, 4.57 mm
- #14 drill bit — 0.182 in, 4.62 mm
- #13 drill bit — 0.185 in, 4.7 mm
- 3/16" drill bit — 0.1875 in, 4.76 mm
- #12 drill bit — 0.189 in, 4.8 mm
- #11 drill bit — 0.191 in, 4.85 mm
- #10 drill bit — 0.1935 in, 4.91 mm