Surface Grinder Spindle Rebuild Recommendations, Ballpark Costs

Hi Folks,

I recently picked up a Chevalier Smart B818-II as surplus. Its definitely in need of some love and a new enclosure. The machine itself is mechanically (ways and ballscrews) and electrically in good shape, but it appears someone might have crashed it at some point. The spindle bearings are still silky smooth with no detectable play, but there is .0002 runout at the root of the spindle nose taper and .0005 at the tip and both are clocked at the same angle, so it appears that the spindle nose was slightly bent. I'm looking to get a recommendation for a quality spindle repair facility that doesn't overcharge for fluffy "value add" nonsense (I don't need a DNA workup for what species of gnat farted in my spindle oil, causing fatal contamination, for example. :) ).

I'm expecting bearing replacement, but not sure how you handle the spindle nose if its bent by such a small amount.

Anyone had a recent spindle rebuild that involved this kind if issue that would be willing to share some ballpark repair costs, repair facility used, and overall satisfaction with the quality and value of their work?

Thanks!

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Originally Posted by tcom-frazzled

Hi Folks,

I recently picked up a Chevalier Smart B818-II as surplus. Its definitely in need of some love and a new enclosure. The machine itself is mechanically (ways and ballscrews) and electrically in good shape, but it appears someone might have crashed it at some point. The spindle bearings are still silky smooth with no detectable play, but there is .0002 runout at the root of the spindle nose taper and .0005 at the tip and both are clocked at the same angle, so it appears that the spindle nose was slightly bent. I'm looking to get a recommendation for a quality spindle repair facility that doesn't overcharge for fluffy "value add" nonsense (I don't need a DNA workup for what species of gnat farted in my spindle oil, causing fatal contamination, for example. :) ).

I'm expecting bearing replacement, but not sure how you handle the spindle nose if its bent by such a small amount.

Anyone had a recent spindle rebuild that involved this kind if issue that would be willing to share some ballpark repair costs, repair facility used, and overall satisfaction with the quality and value of their work?

Thanks!

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And once you put the Grinding wheel arbor on the spindle and dress the wheel balance it, and then see how well the surface cut is that runout may not make any difference to the finish Ground surface, the spindle could be reground in place, if the Bearings are good, don't take it apart, any spindles like this would need to be Ground in its own housing so on the machine is best, it was most likely like that from new, or this is just from wear from wheel changes, I would not spend too much money on it if everything works just clean it up and use it.

Thanks for the feedback. I turned here after dressing and balancing and having a tough getting a decent finish. It became apparent when I saw the runout in the taper. I am balancing with near zero runout on the balancing arbor and then introduce post-balancing runout when I install the wheel. Its a losing battle. You would need to be able to balance the wheel with the exact same runout in place in order to get the center of mass and center of rotation coincident.

I know there are a number of negative viewpoints out there on the Chevalier machines. In my case, I picked it up for next to nothing, fully expecting it to be a bit of a project machine that would need some attention and investment. I enjoy doing the rebuild and improvements and its not a machine that I have work lined up and waiting for, its more of a pet project for the moment. I don't see anything about the design that is fundamentally awful, so my hope is to get it dialed in so its actually as good or maybe even better than new with some attention to detail that may have been overlooked when it was originally built. Its a cartridge spindle, so it can easily be removed and sent in for repair, regrind, and dynamic rebalance. In the long run, profile / 4 axis grinding is going to be a lot of what I want to be able to do with it, so the spindle needs to be brought back in spec.

I'll make a few phone calls for budgetary estimates this week, I'm just looking for sound recommendations on who to send it to. I had ballscrews for one of my machining centers reconditioned a while back and the place I sent them to turned out to be a complete joke. I wasted quite a bit of money on that endeavor and ended up with really subpar workmanship.

Quote:

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Originally Posted by tcom-frazzled

Thanks for the feedback. I turned here after dressing and balancing and having a tough getting a decent finish. It became apparent when I saw the runout in the taper. I am balancing with near zero runout on the balancing arbor and then introduce post-balancing runout when I install the wheel. Its a losing battle. You would need to be able to balance the wheel with the exact same runout in place in order to get the center of mass and center of rotation coincident.

I know there are a number of negative viewpoints out there on the Chevalier machines. In my case, I picked it up for next to nothing, fully expecting it to be a bit of a project machine that would need some attention and investment. I enjoy doing the rebuild and improvements and its not a machine that I have work lined up and waiting for, its more of a pet project for the moment. I don't see anything about the design that is fundamentally awful, so my hope is to get it dialed in so its actually as good or maybe even better than new with some attention to detail that may have been overlooked when it was originally built. Its a cartridge spindle, so it can easily be removed and sent in for repair, regrind, and dynamic rebalance. In the long run, profile / 4 axis grinding is going to be a lot of what I want to be able to do with it, so the spindle needs to be brought back in spec.

I'll make a few phone calls for budgetary estimates this week, I'm just looking for sound recommendations on who to send it to. I had ballscrews for one of my machining centers reconditioned a while back and the place I sent them to turned out to be a complete joke. I wasted quite a bit of money on that endeavor and ended up with really subpar workmanship.

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With lapping the spindle taper you could most likely correct the small amount of runout you have; the other thing is the bearings may not be as good as you think, they really determine the surface finish and the balance of the wheel


So did you mount the wheel Dress it, remove the wheel and balance it, replace the wheel and redress it, if you did not do it like this then you will never get a good finish

Agreed that I may find other contributing issues. I balanced, mounted, dressed, unmounted, rebalance, and re-dressed. I was able to get workable results when I made sure that I maintained the clocking of the wheel to the taper every time.

Just to gather a bit more info, I dropped from an 8 inch wheel to 6 and went through a third, very meticulous balance cycle and I was able to get an excellent finish on the latest test grind, so I'm pretty sure the bearings are in good shape.

I hadn't thought about lapping to deal with the runout. I generally only go that route for precision sizing. I'll have to give that process some thought.

Sent from my SM-G998U1 using Tapatalk

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Originally Posted by tcom-frazzled

Agreed that I may find other contributing issues. I balanced, mounted, dressed, unmounted, rebalance, and re-dressed. I was able to get workable results when I made sure that I maintained the clocking of the wheel to the taper every time.

Just to gather a bit more info, I dropped from an 8 inch wheel to 6 and went through a third, very meticulous balance cycle and I was able to get an excellent finish on the latest test grind, so I'm pretty sure the bearings are in good shape.

I hadn't thought about lapping to deal with the runout. I generally only go that route for precision sizing. I'll have to give that process some thought.

Sent from my SM-G998U1 using Tapatalk

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Yes, you could stone the high spot while following the contour of the taper, then lap it true, (1/2" wide stone 400 / 600 grit fine Dimond lapping paste) I have done many spindles like this with 100% success, yours has a very small amount to correct should be a walk in the park, if it was reground most you will find won't grantee better than .0002"

The fact that you go it to work with a 6" wheel says a lot, it could be the other wheel not quite balanced good enough, or not a good wheel try dressing the sides of the 8" wheel before balancing this sometimes works

I appreciate the guidance. I gave some thought to regrinding the taper using the CNC itself with an NSK Planet 550 air spindle fixtured horizontally to the table to do the regrind. Either way, I'll definitely be looking to do this with the absolute minimal amount of material removal so I don't have any effect on the dynamic balance of the spindle cartridge. I doubt such a small amount, so close to the center of rotation would have any noticeable influence, but definitely something I have in the back of my mind.

Quote:

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Originally Posted by tcom-frazzled

I appreciate the guidance. I gave some thought to regrinding the taper using the CNC itself with an NSK Planet 550 air spindle fixtured horizontally to the table to do the regrind. Either way, I'll definitely be looking to do this with the absolute minimal amount of material removal so I don't have any effect on the dynamic balance of the spindle cartridge. I doubt such a small amount, so close to the center of rotation would have any noticeable influence, but definitely something I have in the back of my mind.

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Its, round so will have no effect on the dynamic balance no matter how you do it.