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- Jul 28, 2017
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Long subject line, sorry about that. I just changed out the deep-groove bearings on my mini lathe for angular contact bearings and may have damaged the new bearings when I installed them. It appears to me that the headstock and spindle design on these lathes is problematic in this regard, because there's no good way to avoid applying a lot of pressure between the inner and outer races at two points of the installation. Here's the deal, assuming that the old bearings have been removed (and likely trashed in the processes):
1. Install the front bearing on the spindle. This can be done while pressing on the inner race so no risk of damage. The spindle has a step-up in diameter to act as a stop for the inner race.
2. Press the spindle into the headstock. Since the outer race doesn't rotate during normal use there is some necessary clearance between the spindle and outer race -- therefore, the force needed to press the outer race into the headstock has to be transferred through the bearing balls and inner race. Potential for damage here.
3. Press the rear bearing onto the spindle and into the headstock. Like the front bearing, the spindle and headstock are interference fits to the bearing. As in step 2, force must be transferred through the bearing to install it. Also potential for damage, but using a stepped washer with exactly the right step height and diameters might address this. But you need to make what you need BEFORE you tear your lathe apart, assuming your lathe is running well enough to do so.
For tapered roller bearings I'm thinking that the chances of damage are lower, for several reasons. For one thing. the reduced contact area of bearing balls relative to roller bearings favors roller bearings. The other major difference is that the inner and outer races of a tapered roller bearing can be installed separately. So the forces needed to install them also can be separated.
Based on these considerations, it seems to me that tapered roller bearings are the best way to go, despite some minor issues like needing to reduce the spacer lengths because these bearings are slightly thicker.
What are other folks' experiences in this?
1. Install the front bearing on the spindle. This can be done while pressing on the inner race so no risk of damage. The spindle has a step-up in diameter to act as a stop for the inner race.
2. Press the spindle into the headstock. Since the outer race doesn't rotate during normal use there is some necessary clearance between the spindle and outer race -- therefore, the force needed to press the outer race into the headstock has to be transferred through the bearing balls and inner race. Potential for damage here.
3. Press the rear bearing onto the spindle and into the headstock. Like the front bearing, the spindle and headstock are interference fits to the bearing. As in step 2, force must be transferred through the bearing to install it. Also potential for damage, but using a stepped washer with exactly the right step height and diameters might address this. But you need to make what you need BEFORE you tear your lathe apart, assuming your lathe is running well enough to do so.
For tapered roller bearings I'm thinking that the chances of damage are lower, for several reasons. For one thing. the reduced contact area of bearing balls relative to roller bearings favors roller bearings. The other major difference is that the inner and outer races of a tapered roller bearing can be installed separately. So the forces needed to install them also can be separated.
Based on these considerations, it seems to me that tapered roller bearings are the best way to go, despite some minor issues like needing to reduce the spacer lengths because these bearings are slightly thicker.
What are other folks' experiences in this?