| b |
shaft diameter |
| c |
outer diameter of hub |
| d |
nominal thread diameter |
 |
radial interference of parts when both are same temperature |
| E |
modulus of elasticity of shaft and hub (30 x 106 psi for steel) |
| Fn |
normal force |
| h |
key height (external to shaft) |
| k |
friction factor (k = 0.2 for unplated screws) |
| l1 |
distance from shaft centerline to end of slot |
| l2 |
distance from screw centerline to end of slot |
| Lh |
hub length |
| Lk |
key length |
| Ls |
shaft length |
| n |
number of screws used |
| R |
radius to shaft hub interface, equal to b/2 (b = 2R) |
| T |
applied torque |
| t |
torque applied to nut |
| w |
key width |
| µ |
coefficient of friction (typically 0.8 for steel on steel and 0.6 for aluminum on steel) |