Thanks!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.
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?
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.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.
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.
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.
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.
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.