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2 X 48 Belt Grinder (again)
- Thread starter rwm
- Start date
- Joined
- Mar 25, 2013
- Messages
- 4,611
Update: I am still having problems with upper pulley bearing failure. It is running at 9K rpm. I will need to redesign it with precision (possibly metric) bearings that are more capable.
I am looking at going with an R8-2RS bearing. This will accept the 1/2" shaft but the bearing OD is smaller than the original design. Hence I will need to remake the pulley. This bearing is rated to 15K rpm.
The current bearing is a SKF 1621. I cannot find these from any manufacturer that are rated for these speeds. Any bearing experts out there please chime in!
I'm pretty sure the engineering department is going to take some heat on this.
Robert
I am looking at going with an R8-2RS bearing. This will accept the 1/2" shaft but the bearing OD is smaller than the original design. Hence I will need to remake the pulley. This bearing is rated to 15K rpm.
The current bearing is a SKF 1621. I cannot find these from any manufacturer that are rated for these speeds. Any bearing experts out there please chime in!
I'm pretty sure the engineering department is going to take some heat on this.
Robert
Last edited:
- Joined
- Mar 25, 2013
- Messages
- 4,611
I started working on a new upper pulley axle. It is 17mm dia so it will fit the bore of the new bearings. They are rated at 12K rpm.
Ignore the minor shaft corrosion. I plan to have a spacer seen in the top of the pic which will hold the inner races at the proper distance. I need to cut wrench flats in the middle of the shaft. Yes I cut them there threads. 1/2-13. Boy the carriage moves fast on those coarse threads. I should have picked 1/2-20!
Robert
Ignore the minor shaft corrosion. I plan to have a spacer seen in the top of the pic which will hold the inner races at the proper distance. I need to cut wrench flats in the middle of the shaft. Yes I cut them there threads. 1/2-13. Boy the carriage moves fast on those coarse threads. I should have picked 1/2-20!
Robert
- Joined
- Sep 28, 2013
- Messages
- 4,300
have you thought about plain shielded bearings - they usually run cooler at high speeds than those with rubber shields. Another option might be to remove a shield, clean out the grease and then repack with a small amount of high end high temp bearing grease (like Kluber or similar).
- Joined
- Jan 2, 2016
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- 1,953
Why not go to a larger wheel, and slow the bearings down?
- Joined
- Mar 25, 2013
- Messages
- 4,611
At this point a larger wheel would mean a complete redesign. I made an engineering error originally by selecting high load, low speed bearings and building the pulley around those. I am confident the new precision bearings will last at 9K rpm. The shaft redesign also guarantees better alignment of the races.
I really like this tool and I get a lot of use out of it.
Robert
Edit: I should note that after accurate measurement, my top pulley is turning at 7590 rpm so I really should be fine with the new bearings. The old bearings were only rated to 5K rpm.
Robert
I really like this tool and I get a lot of use out of it.
Robert
Edit: I should note that after accurate measurement, my top pulley is turning at 7590 rpm so I really should be fine with the new bearings. The old bearings were only rated to 5K rpm.
Robert
Last edited:
- Joined
- Mar 25, 2013
- Messages
- 4,611
Here you can see one of the new bearings mounted on the shaft with the spacer.
And here is the pulley and outer bearing installed:
Runs great! Very smooth. Time will tell if this is a durable fix. Calling it done for now.
Robert
And here is the pulley and outer bearing installed:
Runs great! Very smooth. Time will tell if this is a durable fix. Calling it done for now.
Robert