Z drill bit size
0.413 in
10.49 mm · letter drill
| Inches | 0.413 in |
| Millimetres | 10.49 mm |
| Nearest metric drill | 10.5 mm |
| System | Letter (A to Z) |
What Z means
A bit marked Z is a letter drill. Letters run A to Z and get larger as they advance, covering 0.234 to 0.413 inches — the gap between the largest number drill and the point where fractional sizes become fine enough to be useful.
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 Z:
| System | Nearest size | Difference |
|---|---|---|
| number | #1 — 0.228 in | 0.185 in smaller |
| fractional | 13/32" — 0.4063 in | 0.0067 in smaller |
| metric | 10.5 mm | 0.01 mm larger |
The closest substitute is 0.0067 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 0.413 inches
Clearance holes for bolts up to about half an inch, and tapping drills for the larger unified threads. Above a quarter inch a hand drill starts to want two hands and a slower speed, and the bit wants a pilot hole.
Either side of it
| Drill | Inches | Millimetres |
|---|---|---|
| X | 0.397 in | 10.08 mm |
| Y | 0.404 in | 10.26 mm |
| 13/32" | 0.4063 in | 10.32 mm |
| Z | 0.413 in | 10.49 mm |
| 27/64" | 0.4219 in | 10.72 mm |
| 7/16" | 0.4375 in | 11.11 mm |
| 29/64" | 0.4531 in | 11.51 mm |
Frequently asked questions
What size is a Z drill bit?
0.413 inches, which is 10.49 mm. Letter drills run A to Z and get larger as the letter advances, filling the gap between the largest number drill and the fractional sizes.
What is a Z drill bit in mm?
10.49 mm. A metric index will offer 10.5 mm as the nearest stocked size, which is near enough identical.
Is Z a tapping drill size?
Not for any of the unified threads on this site. The next size up, 27/64", is the tapping drill for 1/2-13.
What is the next size up from Z?
27/64" at 0.4219 inches — 0.0089 inches larger. Below it is 13/32" at 0.4063.
Other sizes
- 27/64" drill bit — 0.4219 in, 10.72 mm
- 7/16" drill bit — 0.4375 in, 11.11 mm
- 29/64" drill bit — 0.4531 in, 11.51 mm
- 15/32" drill bit — 0.4688 in, 11.91 mm
- 31/64" drill bit — 0.4844 in, 12.3 mm
- 1/2" drill bit — 0.5 in, 12.7 mm
- 33/64" drill bit — 0.5156 in, 13.1 mm
- 17/32" drill bit — 0.5313 in, 13.49 mm