Abstract: An apparatus is disclosed to rotate a gear shaft about a reference axis and to position rolling path support elements such that their centers coincide with a reference axis. Once the rolling path elements have been centered and adjusted to compensate for any offset or warp they are fixedly attached to the gear shaft and serve to accurately support the shaft in a grinding or machining device which forms internal centering chamfers. Once the centering chamfers have been formed, they may be used to support the device during its final machining. A computer is included in the apparatus and is operatively connected to rotating and feeler devices. The computer is also operatively connected to a display screen which displays a sequence of events enabling the operator to adjust the positions of the rolling path elements. The display screen may include infrared heat sensitive areas to enable the operator to input data into the computer and control the operation of the apparatus.