 Previous Page 310.3
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Bearing
Removal
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Background One of the most common jobs an electrician performs is changing bearings. When bearings are removed properly, it is a relatively simple, quick job. When done improperly, damage can result, causing many man-hours to be lost. The two proper methods of removing bearings are the use of the bearing puller or use of a high-speed grinder.
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Bearing puller method Remove the locknut and spider washer (if installed). Select the correct bearing puller size. Assemble the Type VII bearing puller set. Position the wrench on the inner nut of the bearing puller set. Position the soft center between the pulling attachment jackscrew and shaft end.
Use the correct size wrench to hold the jacking screw while turning the jacking nut (the inside nut). Note bearing movement. Continue turning the inside nut. The bearing should come off the bearing journal.
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Click on image
to enlarge. Use of Bearing Pullers
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Seized bearing removal
If the bearing does not move after using a bearing puller set with moderate pressure, the bearing is seized on the shaft. Use a high-speed grinder to remove the bearing.
Use a high-speed grinder with a NEW cutoff blade to cut the outer race completely through in two places 180 degrees opposite each other and parallel to the shaft. Cut the ball cage in two places at diametric opposites. Remove the cage and balls. Cut the inner race at two diametrically opposite points parallel to the shaft. Do NOT cut into the shaft or the journal shoulder. Holding the grinder at a 45-degree angle, make two cuts at right angles to the first two cuts. Start the cuts 1/8 to 1/2 inch from the land (journal shoulder). This cut reduces the thickness of the metal at the land and provides a relief.
Use a cold chisel and a ball peen hammer to split the inner race off the shaft. Place the point of the chisel directly into the groove cut by the grinder. After bearing removal Regardless of which bearing removal method was used, visually inspect and clean the shaft bearing journal.
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Click on image
to enlarge. Seized Bearing Removal |
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Take a reading with a snap gage and record the reading on the motor data sheet (mechanical). Route to the machine shop if journal repairs are required. |
Click on image to
enlarge. Typical Motor Data Sheet (Mechanical) |
Always remove bearings by applying pressure to the inner ring.
When the bearing comes off, ensure that the bearing
puller set does not fall and injure personnel.
While using the high-speed grinder, use rags to
protect the rest of the motor from metal particles.
| Review Questions If you can correctly answer the questions below, you have learned the key points in this lesson. Choose the correct answer for each question, then look at your score below the questions. Review the lesson if you miss any questions. |