5/8-11 Tap Drill Size and Correct Drill Bit
Use a 17/32 drill bit
5/8-11 · 0.5313 in / 13.49 mm · ~75% thread
5/8-11 is a heavy coarse UNC thread for structural and machine work. A 17/32 inch bit is the correct tap drill.
At a glance
| Tap drill | 17/32 |
|---|---|
| Inches | 0.5313 in |
| Millimetres | 13.49 mm |
| Major diameter | 0.625 in |
| Pitch | 0.0909 in |
| Threads per inch | 11 |
Why this size
drillØ = major − (pitch × %thread) = 0.625 − (0.0909 × 0.75) = 0.5568 in → next standard drill 17/32 (0.5313 in / 13.49 mm)
Large threads need accurate pilot holes. The 5/8-11 tap drill of 17/32 in leaves about 75% thread engagement.
Clearance holes for 5/8-11
A clearance hole lets the bolt pass through unthreaded – close fit keeps parts aligned, free fit allows movement.
| Tap drill (cuts threads) | 17/32 |
|---|---|
| Close fit clearance | 21/32 bit |
| Free fit clearance | 47/64 bit |
Related sizes
Compare with adjacent threads – coarse, fine and the opposite measurement system: