Do my spindle bearings need to be replaced?

[404estop]

I think I won’t stone it then because precision stones are very expensive and I’m pretty budget sensitive right now.

I do have four new bearings so I won’t need to ration them.

 

[mottrhed]

Im not sure what you are doing with this spindle so if you "just need it to spin for a while" you can disregard my nit picking..but

That is the wrong grease, it is made for primarily for rollers not ball bearings. Will it work, probably, assuming you arent running high DmN, but it will certainly run hotter than with the correct grease.

I dont recognize the bearings, but they almost dont look "precision spindle" spec (p4 or better), with the cage and the face grinds on the races giving it away. Again if youre not looking for super precision and repeatability out of this spindle, you may be fine.

The bearing fits and precision are only as good as the surfaces they sit on, I would advise at a minimum to hit that scored journal with scotch brite or something to knock down the highs. Some v blocks and a micron indicator will tell you how serious they are.

 

[404estop]

@mottrhed oh shoot you are correct, I should have bought NB15 . I'll get the correct grease.

I think you are correct about the bearings too. I tried not to break the bank with these and didn't realize I purchased a sub-par bearing. I may be stuck with these unless some pop up for a good price.

Regarding the scotch brite pads, will do.

 

[mmurray70]

What do you guys recommend to do with the factory grease that comes on the bearings? Do you leave it and add more isoflex or does it need to be flushed out first?

Always wondered this. If you leave it the exact qty might not be right, and your mixing 2 different types of grease. And if you flush it its another chance for contamination.

 

[mottrhed]

A quality bearing that comes pre-greased (from the oem), going into a greased application, just use it as is. Most non-sealed precision bearings do not come greased, in which case you would add the correct amount of the correct grease for the application.

It would not be advisable to mix greases to an unknown quantity.

 

[mmurray70]

A quality bearing that comes pre-greased (from the oem), going into a greased application, just use it as is. Most non-sealed precision bearings do not come greased, in which case you would add the correct amount of the correct grease for the application.

It would not be advisable to mix greases to an unknown quantity.

Thanks!

One other question... what kind of tolerance should I aim for with spacers that affect preload? I have a cat40 spindle with 2 bearings in tandem and 2 spacers in between each bearing. Obviously they need to be the same so each bearing shares the load. I dont have access to surface grinder. Hoping i can get them within couple tenths of each other mounted on a mandrel on a lathe. Would this be acceptable?

 

[mottrhed]

Thanks!

One other question... what kind of tolerance should I aim for with spacers that affect preload? I have a cat40 spindle with 2 bearings in tandem and 2 spacers in between each bearing. Obviously they need to be the same so each bearing shares the load. I dont have access to surface grinder. Hoping i can get them within couple tenths of each other mounted on a mandrel on a lathe. Would this be acceptable?

In short, no a few tenths is not really good enough for a spindle bearing.

There’s a few things at play here, because you’re not only concerned about the height difference in the inner vs outer spacers, you need to have the flatness and perpendicularity real good WHILE having the right offset-if so required. Flatness of spacers, target is inside of 2 microns. Perpendicularity, while tough to measure is easy to screw up, so keep it in the back of your mind whenever changing a spacer.

Back to the original question, mounted preload is a stack up of a bunch of dimensions and factors to achieve a predetermined negative clearance. Problem A is almost always… what should the preload be? Then if by some miracle you can acquire an actual spec, problem B is how do I theoretically achieve it, and then prove it.

I can go on about this, but it’s very spindle/application specific so at best I’d be describing a single scenario that may or may not work for whoever reads this in the future.

 

[TAIWA NUMBA WAAN]

What do you guys recommend to do with the factory grease that comes on the bearings? Do you leave it and add more isoflex or does it need to be flushed out first?

Always wondered this. If you leave it the exact qty might not be right, and your mixing 2 different types of grease. And if you flush it its another chance for contamination.

I'm sure they all recommend the most expensive Kluber Isoflex grease for spindles.....but in reality, your machine doesn't need high speed grease if you're doing under 8,000 RPM. I have previosuly used a type of Japanese made spray-in grease for spindle bearings that has extremely high "tackiness" and viscosity, which coats the bearing surfaces with a super sticky grease that almost feels like mouse trap paper, but slippery. When the balls or rollers roll over it, it squishes and gets less sticky, but it still provides a very smooth feeling spindle at the cost of higher initial heat generation and higher drag force at low speeds compared to a high speed grease.

So just keep in mind that if you're running your spindle at medium speeds or less, grease is not nearly as critical as everyone makes it out to be. If you have an old machine and you just want to make chips and hold tolerances of 0.001", you can get away with a lot of spindle abuse and kick the can down the road.

Factory built new machines with demanding specs can't do this of course.

 

[mmurray70]

In short, no a few tenths is not really good enough for a spindle bearing.

There’s a few things at play here, because you’re not only concerned about the height difference in the inner vs outer spacers, you need to have the flatness and perpendicularity real good WHILE having the right offset-if so required. Flatness of spacers, target is inside of 2 microns. Perpendicularity, while tough to measure is easy to screw up, so keep it in the back of your mind whenever changing a spacer.

Back to the original question, mounted preload is a stack up of a bunch of dimensions and factors to achieve a predetermined negative clearance. Problem A is almost always… what should the preload be? Then if by some miracle you can acquire an actual spec, problem B is how do I theoretically achieve it, and then prove it.

I can go on about this, but it’s very spindle/application specific so at best I’d be describing a single scenario that may or may not work for whoever reads this in the future.

This is for a Fadal spindle. It uses 2 7012 bearings in tandem on the bottom, and 2 7210 bearings in tandem on top. The bottom bearings have a 2" spacer in between inner and outer rings. So really need to get the spacers equal lengths so both bearings share the load. In my case the spacer length doesn't really set preload, but it changes how its shared between 2 bearings in tandem. Some fadal spindles actually use only one 7012 bearing for thrust (back to back on bottom and floating on top) so if im off a little, worst case is i just loose some of the extra capacity from the 2 vs 1 thrust bearing.

Preload is set by a nut on top. They have a procedure for setting prelaod. Load the spindle in z, then load it the other way with the drawbar release piston and measure movement. I think I can handle this no problem.

 

[mottrhed]

I know exactly what you are working on... my only thought is; good luck. That is a completely terrible design. We convert them to a different design so the bearings can be installed back to back, front and rear.

 

[mmurray70]

I know exactly what you are working on... my only thought is; good luck. That is a completely terrible design. We convert them to a different design so the bearings can be installed back to back, front and rear.

Really? There was a guy on the facebook group discussing this a while ago too. He suggested threading the spindle and adding a nut so you can use back to back on the bottom. Then space the top bearings up slightly so they can float in the housing, and mount those back to back too.

I understand the advantages. Really simple, and your guaranteed to get the right preload, better for thermal expansion, but what about the reduced thrust capacity from only one bearing vs 2? We run some big drills sometimes. And operators make mistakes and bump vises etc. The thought of loosing half the thrust capacity seems terrible to me. Id hate to loose any thrust capacity at all.

 

[mottrhed]

While you are right in some aspects, a single 7012 15deg nsk is rated just under 4500lbs permissible axial load by itself. So yes 2 is certainly more rigid, but for most applications converting to b2b would be just fine. We have built many spindles with the converted design and never had an overloading issue. What we do see is reduced operating temperature, much more accuracy in the preload, runout and an overall better running spindle.

If you can get it to run right with the original bearing arrangement, go for it, its just a pain.

 

[mmurray70]

While you are right in some aspects, a single 7012 15deg nsk is rated just under 4500lbs permissible axial load by itself. So yes 2 is certainly more rigid, but for most applications converting to b2b would be just fine. We have built many spindles with the converted design and never had an overloading issue. What we do see is reduced operating temperature, much more accuracy in the preload, runout and an overall better running spindle.

If you can get it to run right with the original bearing arrangement, go for it, its just a pain.

Thanks for the info Mottrhed.

Is this 7012 bearing used by many other brands for cat40 spindles? Is it common for other brands to use just one for thrust or is it normally 2?

I did damage a fadal spindle one time while pecking with a big drill. Some big chips fell into the hole and drill crashed into them at bottom. And this was with the tandem setup. That spindle is still running, but I can hear tiny difference ever since lol.

 

[mottrhed]

7012 is on the smaller side for the front of a 40t spindle. 7012 = 60mm journal, much more common is 7013-7014-7015 size bearings, 65-70-75mm journals respectively.

A single pair is very common, but quadsets are common as well, entirely depends on what the machine was specd for. Trisets are also used somewhat commonly.

 

[mmurray70]

7012 is on the smaller side for the front of a 40t spindle. 7012 = 60mm journal, much more common is 7013-7014-7015 size bearings, 65-70-75mm journals respectively.

A single pair is very common, but quadsets are common as well, entirely depends on what the machine was specd for. Trisets are also used somewhat commonly.

Ok, well if 7012 is on smaller side I think ill stick with the original setup since it should be the toughest arrangement despite its other issues. Probably best match for our jobshop type of work.

Thanks again for all the info. Hard to find good info about spindle rebuilds. I really appreciate it.

 

[mottrhed]

Anytime. Good luck with it, they are a total pain to get right, but it can be done.