If the bearings are intended for re-use, dismounting must be performed most carefully; it is imperative that the extracting tool be applied to the ring to be extracted to prevent the rolling elements from brinelling the raceways. In addition, thin-walled outer rings involve the risk of ring fracture.
With non-seperable bearings, first withdraw the ring with sliding fit from its seat and then dismount the tight-fitted ring. The force required for dismounting is generally higher than the mounting force, since, as time passes, the ring becomes embedded on its seat. Even with loose-fitted rings, fretting corrosion may make dismounting
Dismounting of Cylindrical Bore Bearings
Small bearings are usually dismounted with the aid of mechanical extracting devices or hydraulic presses. These are applied either directly to the tight-fitted ring or to the mating parts, such as the labyrinth ring. Provisionally, small bearings can be driven off their seat with a hammer and a metal drift. The light hammer blows should
be applied evenly round the whole circumference of the tight-fitted ring. Dismounting is greatly facilitated, if extracting slots are provided so that the extractor can be directly applied to the tight-fitted bearing ring.
When the inner ring abuts the shaft shoulder and when no extracting slots are provided, ball bearings, tapered roller bearings and cylindrical roller bearings can be dismounted with a special extractor. With the ball bearing extractor, the clamping piece inserted in the extractor engages with finger-shaped extensions between the balls at the inner ring raceway edge; with extractors for cylindrical and tapered roller bearings the clamping piece engages behind the rollers.
Dismounting of Tapered Bore Bearings
Dismounting of Adapter Sleeve Mounted Bearings
For dismounting bearings directly seated on the tapered shaft or an adapter sleeve, loosen the locking device of the shaft or sleeve nut. Loosen nut by an amount corresponding to the drive-up distance. Drive inner ring off the adapter sleeve or tapered shaft seat by gentle hammer taps, using a soft metal drift or, even better, a piece of tubing. When a press is used, support the adapter sleeve or the loosened adapter sleeve nut and withdraw the bearing from the sleeve.
Dismounting of Withdrawal Sleeve Mounted Bearings
Withdrawal sleeve mounted bearings are removed by means of the extraction nut. For this purpose, the shaft nut must be removed. In difficult cases (for large-size bearings), extraction nuts with additional thrust bolts can be used. A washer is inserted between inner ring and thrust bolts. Dismounting of withdrawal sleeves is much easier and less costly with hydraulic nuts. Withdrawal sleeves projecting beyond the shaft end, should be backed up by a thick-walled support ring.
Heating rings are used for dismounting cylindrical roller bearing and needle roller bearing inner rings without lip or with one lip only. The heating rings of light alloy are radially slotted. Their insulated handles provide for easy handling. With an electric heating plate, the heating rings are heated to a temperature of 200 to 300 °C, placed around the inner ring to be extracted and clamped by means of the handles. The heat is rapidly transferred
from the heating ring to the inner ring. When the tight inner ring fit on the shaft is loosened, withdraw both rings simultaneously. After extraction, remove the inner ring immediately from the heating ring to avoid overheating. Heating rings are of great advantage for occasional withdrawal of small or medium-size bearing rings, each
bearing size requiring its own heating ring.