Ron Rapa
Rapa Electric, Inc.

At Rapa Electric, we’ve had a number of “opportunities” to remove a blind pinion from a motor shaft.

Sometimes, if we’re lucky, the pinion may have a push-off bolt to facilitate removal. And at other times, there may be a through-hole in the rotor shaft so that we can use a push-bar to shove the pinion out of its hole. If we’re not so lucky, we have to use a more creative method.

Those unlucky situations usually involve a metric (IEC) or one-of-a-kind motor, and in most instances come in as a rush/emergency at the start of a holiday weekend. At those times, construction information is usually scarce. 

X-ray vision would be helpful at this point to determine if the pinion is stub-mounted into the parent shaft or mounted over a stub portion of the motor shaft. 

In order to tackle either version, we fabricated a steel “push box” to accommodate different sizes of rotors to aid in the press off or out process (see Figure 1).  

If a proper sized bearing separator is on hand, suspend the rotor in a vertical press by the pinion. Then assemble the “push box” around the rotor ensuring clearance to allow rotor movement with a few inches of clearance above for press travel. See Figures 2 and 3. (If no bearing separator is on hand, a two-piece press block can be fabricated.) The opposite of the pinion end of the shaft is usually tapped, which allows a puller bolt to be inserted up from the bottom.

Once assembled, apply pressure to top of the push box. The box and bolted rotor will move down, leaving the pinion at the top support. Sometimes a little heat is necessary to help loosen the pinion.

Categories: Repair procedures & tips, Service center equipment

Tags: Service center equipment

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