9/16″-12 UNC Thread
Recommended tap drill 31/64″
Tap drill Ø 0.4844″ / 12.303 mm
Major Ø 0.5625″ / 14.287 mm
Threads per inch 12
The chart recommendation gives approximately 72.2% thread engagement — the conventional target for average materials. It is not the only valid choice; see the options below.
Specification
| Designation | 9/16″-12 UNC |
|---|---|
| Thread family | Unified National Coarse (UNC) |
| Nominal size | 9/16 |
| Basic major diameter | 0.5625″ / 14.287 mm |
| Threads per inch / pitch | 12 TPI (2.117 mm pitch) |
| Recommended tap drill | 31/64″ (0.4844″ / 12.303 mm) |
Tap drill options by thread engagement
Any of these standard drills produces a usable engagement for 9/16″-12 UNC; smaller drills give stronger threads but higher tapping torque. Percentages use the conventional approximation (60° thread form).
| Drill | Decimal in | mm | Approx. engagement |
|---|---|---|---|
| 12 mm | 0.4724 | 12 | 83.2% |
| 12.1 mm | 0.4764 | 12.1 | 79.6% |
| 12.2 mm | 0.4803 | 12.2 | 75.9% |
| 12.3 mm | 0.4843 | 12.3 | 72.3% |
| 31/64″ — chart recommendation | 0.4844 | 12.303 | 72.2% |
| 12.4 mm | 0.4882 | 12.4 | 68.6% |
| 12.5 mm | 0.4921 | 12.5 | 65% |
| 12.6 mm | 0.4961 | 12.6 | 61.4% |
Nearest drills to the tap drill in other systems
| Drill | Size | vs 31/64″ | Resulting engagement |
|---|---|---|---|
| 12.3 mm | 0.4843″ / 12.3 mm | −0.003 mm | 72.3% |
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) | 13/16″ |
|---|---|
| Wrench / socket size (nut) | 7/8″ |
| Head height | 23/64″ (0.3594″) |
| Nut thickness | 31/64″ (0.4844″) |
| Compatible nut | 9/16-12 hex nut |
Basic (nominal) dimensions. See the wrench & socket size charts for all sizes and the metric ↔ SAE socket comparison.
Related threads
- 9/16″-18 UNF — same nominal size, 18 TPI (Unified National Fine (UNF)) · compare
- 1/2″-13 UNC — next size down in UNC
- 5/8″-11 UNC — next size up in UNC