BS 325 Black Cup and Countersunk Bolts and Nuts
BS 325:1947 covers black cup and countersunk bolts and nuts. The table shows the published BSW size schedule and the associated drawing dimensions.
Dimensions for BS 325 black cup bolts
| Nominal size d (in.) | BSW threads per inch | dk (in.) | k (in.) | k1 (in.) | n (in.) | s (in.) |
|---|---|---|---|---|---|---|
| 1/4 | 20 | 0.500 | 0.188 | 0.125 | 0.062 | 0.062 |
| 5/16 | 18 | 0.625 | 0.234 | 0.156 | 0.078 | 0.078 |
| 3/8 | 16 | 0.750 | 0.281 | 0.188 | 0.094 | 0.094 |
| 7/16 | 14 | 0.875 | 0.328 | 0.219 | 0.109 | 0.109 |
| 1/2 | 12 | 1.000 | 0.375 | 0.250 | 0.125 | 0.125 |
| 5/8 | 11 | 1.250 | 0.469 | 0.312 | 0.156 | 0.156 |
| 3/4 | 10 | 1.500 | 0.562 | 0.375 | 0.188 | 0.188 |
| 7/8 | 9 | 1.750 | 0.656 | 0.438 | 0.219 | 0.219 |
| 1 | 8 | 2.000 | 0.750 | 0.500 | 0.250 | 0.250 |
Note: All dimensions are in inches. This selected table follows the BS 325 cup-bolt schedule; confirm the bolt form and tolerances against the full standard for production.