posted by Dan at 8:18 AM
TaperLock bushings have been in use in the Power Transmission Industry for over 30 years. With proper application and installation, they are highly reliable components. Based on questions that we receive, though, users should be aware of a couple of preventable pitfalls with their installation.
TaperLock bushings are sometimes accused of loosening after installation. TaperLock bushings need a little help beyond bolt tightening in order to grip hubs and shafts tightly. After the recommended bolt torque has been reached, the bushing faces should be tapped several times with a drift or punch in a circular pattern (don’t hammer bushing faces directly). This seats bushings more deeply into the tapered pulley or sheave hubs, increasing the gripping force. The bolts now need to be re-torqued to the recommended torque level as they will have loosened some. This process ensures that bushings are completely and tightly seated so will not loosen with usage over time.
Shaft keys are sometimes not held securely between shaft and bushing key seats and work out over time. They sometimes literally fall out in vertical shaft applications. This is due to manufacturing tolerance accumulations with shafts, bushings and keys so is only occasional. There are a couple of viable solutions. One is to apply a Loctite type adhesive to keys and key seats during assembly. Another is to punch keys several times on each side with a sharp center punch to raise the key surface slightly around the depressions. This will increase the total key thickness slightly enabling compression between shafts and bushings.