5/8-11 tap drill size
17/32"
- Inches
- 0.5312
- Millimetres
- 13.49
- Thread
- 79%
Drill a 17/32" hole before cutting a 5/8-11 thread. That is the standard tap drill for about 75% thread.
5/8-11 thread and hole sizes
| Thread | 5/8 diameter, 11 threads per inch, coarse (UNC) |
|---|---|
| Major diameter | 0.6250 in 15.88 mm |
| Pitch | 0.0909 in 2.309 mm |
| Tap drill, about 75% thread | 17/32" 0.5312 in |
| Tap drill, about 50% thread | 9/16" 0.5625 in, for stainless and other hard materials |
| Clearance hole, close fit | 41/64" 0.6406 in |
| Clearance hole, free fit | 21/32" 0.6562 in |
| Nearest metric bit | 13.5 mm |
Why 17/32"
A tap cuts threads into the wall of a hole, so the hole has to be smaller than the screw. For a 5/8-11 thread the hole that leaves exactly 75% thread is 0.5364 in. The closest standard bit is 17/32" at 0.5312 in, which leaves 79%.
More thread than that adds almost no strength and makes the tap much easier to break. In hard or tough material, go one step larger.
Tools for this job
- 5/8-11 tap
- 17/32" drill bit
- Tap and drill set
- Drill bit size gauge
- Thread pitch gauge
- Cutting oil for tapping
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