P drill bit size
0.323 in
8.2 mm · letter drill
| Inches | 0.323 in |
| Millimetres | 8.2 mm |
| Nearest metric drill | 8.2 mm |
| System | Letter (A to Z) |
What P means
A bit marked P 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 P:
| System | Nearest size | Difference |
|---|---|---|
| number | #1 — 0.228 in | 0.095 in smaller |
| fractional | 21/64" — 0.3281 in | 0.0051 in larger |
| metric | 8.2 mm | identical |
The closest substitute is 0.0051 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 0.323 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 |
|---|---|---|
| N | 0.302 in | 7.67 mm |
| 5/16" | 0.3125 in | 7.94 mm |
| O | 0.316 in | 8.03 mm |
| P | 0.323 in | 8.2 mm |
| 21/64" | 0.3281 in | 8.33 mm |
| Q | 0.332 in | 8.43 mm |
| R | 0.339 in | 8.61 mm |
Frequently asked questions
What size is a P drill bit?
0.323 inches, which is 8.2 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 P drill bit in mm?
8.2 mm. A metric index will offer 8.2 mm as the nearest stocked size, which is near enough identical.
Is P 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 P?
21/64" at 0.3281 inches — 0.0051 inches larger. Below it is O at 0.316.
Other sizes
- 21/64" drill bit — 0.3281 in, 8.33 mm
- Q drill bit — 0.332 in, 8.43 mm
- R drill bit — 0.339 in, 8.61 mm
- 11/32" drill bit — 0.3438 in, 8.73 mm
- S drill bit — 0.348 in, 8.84 mm
- T drill bit — 0.358 in, 9.09 mm
- 23/64" drill bit — 0.3594 in, 9.13 mm
- U drill bit — 0.368 in, 9.35 mm