An employee was showing a second employee how to install a drive shaft onto a rotor plate. The drive shaft had to be aligned and seated onto the rotor plate by using a leather mallet and striking the drive shaft repeatedly. While attempting to stabilize the drive shaft, the second employee placed his index finger on the end of the shaft. The first employee struck the second employee's finger against the drive shaft with the leather mallet, crushing his left index finger, which had to be surgically amputated.