Denford Software & Machines

Hi

[Edit: Do not use the method described in the first part of this post. Use the bolt/joiner nut method described further down. ]

I used a 10mm threaded rod and a wooden frame to apply tension to the spindle. With enough tension, the inside bearing race of the left taper bearing moved along the spindle allowing the spindle to be extracted. The outer bearing race squeezed the inner race along the spindle.

Note that simply hauling out the spindle is not the way I would do this job again with the benefit of hindsight. The problem is that because of the taper on the bearing race, the clamping force is far greater than the pulling force. Applying tension on the spindle causes the out bearing race to squeeze the inner race. The clamping force is multiple times greater than the applied tension. As a result, very high tension is required to extract the spindle.


Extracting the spindle was a two step process. Firstly, the inner taper race needs to be removed, then a sleeve on the shaft needs to be removed by packing the gear set and applying tension. I packed the gearset with two scraps of wood.

If I did this job again, I would use a different method. I would make this a one step process. I would use a pair of joiner nuts and standard bolts (joiner nuts are long nuts designed to join threaded rod end to end). With the bolts fully screwed into the nuts, I would cut the assembly to a length that would allow them to fit where the wooden packing is shown. I would then unscrew the joiner nuts and bolts to push the gearset hard against the sleeve at the other end of the spindle. The sleeve would push the inner taper bearing race at the gear end of the spindle.

If the joiner nuts and bolts are expanded enough, they would push off the sleeve and inner bearing race. The difficult access and limited expansion length wouldn't make this practical. With enough pressure pushing axially on the bearing inner race, applying additional tension to extract the spindle would significantly reduce the clamping pressure exerted by the outer bearing race. This would dramatically reduce the tension required to extract the spindle.

Hi

When I was doing final tightening up of the spindle bearing locknuts, I made a mistake and ended up with too much pre-load on the spindle bearings. A no-load high speed run confirmed that bearing operating temperatures were too high.

I needed to loosen the locknuts (easy) and partly remove the bearing (hard) to start the adjustment process over again. Rather than use the brute force method for hauling out the bearing, I used bolts and joiner nuts as expanding spacers as proposed in the previous post. I just needed to move the bearing race along the shaft a millimetre or so.

The shaft spacer behind the bearing is held in place with two set screws. It's there to hold the gear in place. It doesn't contact the bearing race. With the set screws removed, the shaft spacer can be slid to the right as seen in the images to push on the bearing race. The gears also slide along the shaft. Together, the gears and the shaft spacer form a tube around the spindle. The expanding spacers push this tube along the spindle. With the expanding spacers in place and tightened, pressure is applied to the inner bearing race on the gear end of the spindle.

It was too difficult to tighten the expanding spacers by much. There is little room to move. I tightened the spacers as much as I could. Then couple of moderate soft-face hammer blows were enough to move the bearing race a milli-metre as required.

This method needed only a fraction of the force required to simply haul out the bearing. It works on this lathe because of the particular arrangement of gears and the shaft spacer. It greatly reduces the risk of damaging something. This method could easily be combined with the threaded rod rig to apply extra pressure to a stuck bearing.