TM  10-3930-643-34 GENERAL  MAINTENANCE  PROCEDURES. 2-14. Bearing  Procedures. c. Inspection. Bearings are inspected by holding the inner race so that the axis is vertical (bearing horizontal). Turn  the  outer  race slowly. Bearing may have a small amount of tarnish,    stain, or corrosion on the outside surfaces of the races. Operation of the bearing is not affected and they need not be rejected. If bearings feel slightly rough or have a tendency to stick at certain points when rotated, reclean. Determine cause of sticking and reject if necessary. Reject bearings with the following defects: broken or cracked races, dented shields or seals, cracked or broken separators, balls or rollers,  flaked  areas  on  balls,  rollers  or  raceways,  bearings  with signs of heating (darkened to brownish blue or blue black), and indentations from ball or roller impressions. An anti-friction bearing, properly lubricated, should not wear unless dirt or abrasive foreign matter gets into it. Dirt mixed with grease or oil will lap down balls and rollers. Load  carrying  surfaces  of  anti- Friction bearings are finished with extreme care and will sustain very heavy loads unless the surfaces are damaged by abusive handling or by foreign matter. d. Bearing  Installation. (1) Before installing bearings, clean shafts and bearing housings thoroughly. Remove all dirt from keyways, splines, and grooves. Remove burrs and slivers. If new bearings are to be used, keep them in their original cartons or wrappings until ready for use. New bearings are shipped with a protective  lubricant. Do not clean the oil or grease from a new bearing. Handle the bearing with clean hands and use clean tools to install. Before installing bearings, make sure bearing seats are cleaned and oiled. (2) Press bearings only on the tight fitting race and press straight and square. The  same  protective  measures  for  shafts  and  bearings  used  during removal  should  be  applied  during  installation. (3) In some applications, bearings must be heated to ensure proper fit. A bearing may be heated in a temperature controlled oven or in clean oil at a temperature of 200 to 250 degrees F. The high temperature expands the inner race enough to allow it to slip over the shaft to the bearing seat. Do not overheat  bearing.  Overheating  will  cause  bearing  to  lose  hardness.  If expanding race will not allow installation of the bearing, freeze shaft in dry ice for approximately 30 minutes. Chilling will cause shaft to shrink enough to  allow  bearing  installation. 2-27(2-28  blank)