H drill bit size
0.266 in
6.76 mm · letter drill
| Inches | 0.266 in |
| Millimetres | 6.76 mm |
| Nearest metric drill | 6.8 mm |
| System | Letter (A to Z) |
What H means
A bit marked H 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 H:
| System | Nearest size | Difference |
|---|---|---|
| number | #1 — 0.228 in | 0.038 in smaller |
| fractional | 17/64" — 0.2656 in | 0.0004 in smaller |
| metric | 6.8 mm | 0.044 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 0.266 inches
Where the quarter-inch and five-sixteenths taps are drilled, and where clearance holes for small bolts begin. The three drill systems overlap most densely across this band, which is why a bit here is the one most often picked up and misidentified.
Either side of it
| Drill | Inches | Millimetres |
|---|---|---|
| F | 0.257 in | 6.53 mm |
| G | 0.261 in | 6.63 mm |
| 17/64" | 0.2656 in | 6.75 mm |
| H | 0.266 in | 6.76 mm |
| I | 0.272 in | 6.91 mm |
| J | 0.277 in | 7.04 mm |
| K | 0.281 in | 7.14 mm |
Frequently asked questions
What size is a H drill bit?
0.266 inches, which is 6.76 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 H drill bit in mm?
6.76 mm. A metric index will offer 6.8 mm as the nearest stocked size, which is 0.044 mm larger — enough to matter when tapping and not enough to matter for a clearance hole.
Is H a tapping drill size?
Not for any of the unified threads on this site. The next size up, I, is the tapping drill for 5/16-24.
What is the next size up from H?
I at 0.272 inches — 0.006 inches larger. Below it is 17/64" at 0.2656.
Other sizes
- I drill bit — 0.272 in, 6.91 mm
- J drill bit — 0.277 in, 7.04 mm
- K drill bit — 0.281 in, 7.14 mm
- 9/32" drill bit — 0.2813 in, 7.14 mm
- L drill bit — 0.29 in, 7.37 mm
- M drill bit — 0.295 in, 7.49 mm
- 19/64" drill bit — 0.2969 in, 7.54 mm
- N drill bit — 0.302 in, 7.67 mm