5/8-11 Tap Drill Size & Thread Specs
Everything for a 5/8-11 UNC thread on one page: tap drill (17/32), clearance holes, wrench and hex key sizes, and the nearest metric thread.
SP-TD-01 · 5/8-11
5/8-11 specs
SizePlate
5/8-11 UNC · tap with
17/32 drill
.5313″
13.5 mm · 79% thread
- Metric drill
- 13.5 mm · .5315
- Clearance
- 41/64 / 21/32
- Wrench
- 15/16″
- Cap screw key
- 1/2″
Thread
- Nominal size
- 5/8″ · 15.88 mm
- Major diameter
- .6250″
- Threads per inch
- 11
- Pitch
- .0909″ · 2.309 mm
- Series
- UNC (coarse)
- UNF version
- 5/8-18
Drilling
- Tap drill (75%)
- 17/32 · .5313
- Metric substitute
- 13.5 mm · .5315
- Tap drill (≈50%)
- 9/16 · .5625
- Close fit
- 41/64 · .6406
- Free fit
- 21/32 · .6563
Tools
- Hex bolt wrench
- 15/16″
- Hex nut wrench
- 15/16″
- Socket head cap key
- 1/2″
- Button head key
- 3/8″
- Flat head key
- 3/8″
Nearest metric
- Thread
- M16 × 2.0
- Major diameter
- 16 mm
- Pitch
- 2 mm
- Tap drill
- 14 mm
- Interchangeable
- No
Not interchangeable means the threads look close but won't run together: forcing one into the other strips both.
Drill size by thread percentage
Larger drill, less thread, easier tapping. 75% is the usual target.
| Drill | Decimal | mm | Thread |
|---|---|---|---|
| 17/32 | .5313 | 13.5 | 79% |
| 13.5 mm | .5315 | 13.5 | 79% |
| 35/64 | .5469 | 13.89 | 66% |
| 14 mm | .5512 | 14 | 63% |
| 9/16 | .5625 | 14.29 | 53% |
| 14.5 mm | .5709 | 14.5 | 46% |
Neighboring sizes
Questions
What does 5/8-11 mean?
A 5/8″ nominal diameter with 11 threads per inch. It’s the coarse (UNC) thread for that size; the fine version is 5/8-18.
Can I use a 13.5 mm drill instead of 17/32?
Usually. 13.5 mm is .5315″ against .5313″ for 17/32, which changes the thread engagement by a few percent at most. The thread-percentage table above shows exactly how much thread each nearby drill leaves.