5/8″-11 UNC Thread
The chart recommendation gives approximately 79.4% thread engagement — the conventional target for average materials. It is not the only valid choice; see the options below.
Specification
| Designation | 5/8″-11 UNC |
|---|---|
| Thread family | Unified National Coarse (UNC) |
| Nominal size | 5/8 |
| Basic major diameter | 0.6250″ / 15.875 mm |
| Threads per inch / pitch | 11 TPI (2.309 mm pitch) |
| Recommended tap drill | 17/32″ (0.5313″ / 13.494 mm) |
Tap drill options by thread engagement
Any of these standard drills produces a usable engagement for 5/8″-11 UNC; smaller drills give stronger threads but higher tapping torque. Percentages use the conventional approximation (60° thread form).
| Drill | Decimal in | mm | Approx. engagement |
|---|---|---|---|
| 17/32″ — chart recommendation | 0.5313 | 13.494 | 79.4% |
| 13.5 mm | 0.5315 | 13.5 | 79.2% |
| 35/64″ | 0.5469 | 13.891 | 66.2% |
| 14 mm | 0.5512 | 14 | 62.5% |
Nearest drills to the tap drill in other systems
| Drill | Size | vs 17/32″ | Resulting engagement |
|---|---|---|---|
| 13.5 mm | 0.5315″ / 13.5 mm | +0.006 mm | 79.2% |
Clearance holes
For a bolt or screw of this size to pass through freely. Recommended drills per ASME B18.2.8: close, normal, and loose fits.
| Fit | Drill / Ø | Decimal in | mm |
|---|---|---|---|
| close | 21/32″ | 0.6563 | 16.669 |
| normal | 11/16″ | 0.6875 | 17.462 |
| loose | 47/64″ | 0.7344 | 18.653 |
Hex bolt & nut dimensions
For a standard hex cap screw (ASME B18.2.1) and finished hex nut (ASME B18.2.2) in this size.
| Wrench / socket size (bolt head) | 15/16″ |
|---|---|
| Head height | 25/64″ (0.3906″) |
| Nut thickness | 35/64″ (0.5469″) |
| Compatible nut | 5/8-11 hex nut |
Basic (nominal) dimensions. See the wrench & socket size charts for all sizes and the metric ↔ SAE socket comparison.
Related threads
- 5/8″-18 UNF — same nominal size, 18 TPI (Unified National Fine (UNF)) · compare
- 9/16″-12 UNC — next size down in UNC
- 3/4″-10 UNC — next size up in UNC