| THREAD SERIES DESIGNATOR | UNC |
| NOMINAL THREAD DIAMETER | 0.250 INCHES |
| THREAD QUANTITY PER INCH | 20 |
| THREAD CLASS | 2A |
| THREAD DIRECTION | RIGHT-HAND |
| THREAD LENGTH | 0.244 INCHES MINIMUM AND |
| 0.375 INCHES MAXIMUM |
| FASTENER LENGTH | 0.344 INCHES MINIMUM AND |
| 0.375 INCHES MAXIMUM |
| MATERIAL | STEEL COMP 1050 OR |
| STEEL COMP 1566 OVERALL |
| MATERIAL DOCUMENT AND CLASSIFICATION | SAE ASSN STD ALL MATERIAL RESPONSES PRIMARY WASHER |
| SAE ASSN STD SINGLE MATERIAL RESPONSE FASTENER |
| SURFACE TREATMENT | CADMIUM OR |
| ZINC OVERALL |
| HARDNESS RATING | 40.0 ROCKWELL C MINIMUM AND |
| 50.0 ROCKWELL C MAXIMUM PRIMARY WASHER |
| HEAD STYLE | HEXAGON |
| HEAD HEIGHT | 0.172 INCHES MINIMUM AND |
| 0.190 INCHES MAXIMUM |
| WIDTH BETWEEN FLATS | 0.428 INCHES MINIMUM AND |
| 0.438 INCHES MAXIMUM |
| WASHER QUANTITY | 1 |
| PRIMARY WASHER STYLE | FLAT EXTERNAL TEETH |
| PRIMARY WASHER OUTSIDE DIAMETER | 0.466 INCHES MINIMUM AND |
| 0.478 INCHES MAXIMUM |
| PRIMARY WASHER MATERIAL THICKNESS | 0.025 INCHES NOMINAL |
| SPEC/STD CONTROLLING DATA | |
| MANUFACTURERS CODE | 21450 |
| DEFINITIVE GOVERNMENT SPEC/STD REFERENCE | 425323 |