Precision machining of the tapered bore in the hub of the rim and the tapered mating surface of the bushing insures a snug, precision fit between the rim and bushing. Tightening the cap screws draws the Sheave up tight on the bushing – Standard Bushings are steel and ductile iron.
This feature, together with the tapered, precision fit of rim and bushing, enables SST Bushing to compress evenly around the entire circumference of the shaft, gripping it with tremendous pressure, the equivalent of a press fit on the shaft. This makes it just as easy to install Sheaves on all standard size shafts as it is to install them on shafts which may be slightly oversize or slightly undersize.
To install Sheaves, the cap screws are used as pull-up bolts. Tightening each bolt in turn draws the rim up evenly on the Bushing – pressure is applied by a torque wrench only – no additional leverage is necessary. To remove Sheaves, the cap screws are taken out and used as jack screws. A few quick turns on each screw, and the tight grip of the busing on the shaft is easily broken.
Once the correct position of the Sheave on the shaft is determined, tightening the set screw in the bushing head down on the key will hold the Sheave in this position while the pull-up bolts are tightened. This set screw holds the key in place on the shaft during drive operation – an especially desirable feature on drives that have vertical shafts.
As in the case of SST Sheaves, the Bushings also conform to standardized dimensions and sheave types. Because of this feature, any Stock Bushing may be interchanged with the same size bushing that other manufacturers have produced.