Hubs are usually fastened to shafts by means of setscrews, pins or special fasteners. Whenever the size of hub permits there are 2 setscrews supplied usually 90 apart. The diameter of the setscrew used is dependent on the bore size and the configuration of the hub.
The usual correlation of bores and setscrews is shown on Table 12.
| Inch Size Setscrew |
Shaft Size | Metric Setscrew Size |
|
| Inch | Metric | ||
| 4-40 | .125 | 3 | M2 |
| 4-40, 6-32, 6-40 | .187 | 4 | M2.5 |
| 6-32, 6-40, 8-32 | .250 | 6 | M3 |
| 8-32, 10-32 | .312 | 8 | M4 |
| 10-32 | .375 | 10 | M5 |
| 1/4-20 | .500 | 12 | M6 |
The hub outside diameter should be designed large
enough to accommodate a setscrew which has a length approximately 15 times its diameter. It is a minimum requirement that the setscrew
engagement with the hub must be at least as long as the outside diameter of the setscrew.
A patented FAIRLOC® hub fastener
is available if phasing, positioning or overload protection is required. This clamping feature is based on the following principle:
Two slots are machined into the hub, one oriented radially, the other angularly, to create a transverse wedge
which remains attached to the solid portion of the hub on one side. The resultant cantilevered clamping section has a tapped hole to accept a cap screw which passes through a clearance hole in the solid portion of the hub, and into a threaded hole in the transverse wedge section. As the screw is tightened the cantilevered section clamps the shaft securely. The screw can be tightened and released repeatedly without marring the shaft or affecting its torque transmitting abilities.
T29