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AS9120 & ISO9001 Approved

Mounting/dismounting tapered bore roller bearings

Mounting

Roller bearings with a tapered bore are either fitted directly onto a tapered shaft or onto a cylindrical shaft with an adapter_sleeve or a withdrawal sleeve. By driving up the inner ring on the shaft or sleeve, the tight fit required is obtained and is measured by checking the radial clearance reduction due to the expansion of the inner ring or by measuring the axial drive distance. Check the drive up distance for spherical roller bearings in the 1:12 taper table and the 1:30 taper table. The use of a good quality feeler gauge is imperative for measuring the radial clearance.

Small bearings up to approximately 80mm bore can be pressed with a locknut onto the taper seat of the shaft or the adapter sleeve. A hook spanner should be used to tighten the nut. Small withdrawal sleeves are also pressed with a locknut into the gap between the shaft and the inner ring bore.

Considerable force is required to tighten the nut with medium sized bearings. Locknuts with thrust bolts facilitate mounting in such cases (not suitable for FAG spherical roller bearings of the 'E' design.

It is advisable to use a hydraulic press for driving-up larger bearings or pressing them onto the sleeve. Hydraulic nuts are available for all popular sleeve and shaft threads. For bearings with a bore of 160mm and upwards mounting and dismounting are greatly facilitated by the hydraulic method.

Dismounting

When bearings are directly on the tapered seat or an adapter sleeve, the locking device of the shaft or sleeve is loosened first. The nut is then turned back by the amount corresponding to the drive up distance. The inner ring is then driven off the sleeve or the shaft by means of a hammer and a piece of tubing. When a press is used the adapter sleeve is supported and the bearing pressed off.

Withdrawal sleeve mounted bearings are removed by means of an extraction nut. High forces are required for large sized bearings. Extraction nuts with additional thrust bolts are then used. A washer should be inserted between the bearing inner ring and the thrust bolts.

The dismounting of withdrawal sleeves is much easier and cost effective with hydraulic nuts. The hydraulic method is applied to facilitate the dismounting of large size bearings. Oil is injected between the mating surfaces and enables the mating parts to be moved separately without risking surface damage. Tapered shafts must be provided with oil grooves and supply bores. The required oil pressure has to be created with a pump. When dismounting, an oil with a viscosity of about 150mm2/s at 20 degrees C is used (nominal viscosity 46mm2/s at 40 degrees C. Fretting corrosion can be dissolved by adding rust removing additives to the oil. For tapered bore bearings, oil is pressed between the mating surfaces. Since the press fit is released abruptly, a stop such as a nut should be provided to control the movement of the bearing.

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