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Do my spindle bearings need to be replaced?

Look close at the drawing.
You will see an open and a closed side of the bearing. Angled line, straight line.
This tells you what you need to know.
A good catalog/manual is the "Extra Precision and Instrument Bearings" from Fafnir. Full of good engineering information about spindle bearings.
Never needed the vee marks as that obvious but there are also high spot or runout marks on the better bearings. You align these radially for best performance.
A spindle rebuild on a B-port or a Harig 6x12 is easy. This one a bit harder.
Best of luck.
Measure temps as you run it in. Themocouples best but you can do it by feel of the hand on the housing. It should be warm but not too warm.
If it does not get warm something is wrong. If it gets hot something is wrong.
Jog to distribute the grease at first.
Do not over grease the bearings (this I have seen many times). CC calibrated syringe. They want less than you would think.
Try to make where you are doing it a "clean room".
During removal you will "gall" or mar some surfaces involved. Careful light stoning is often needed.
7 and 9 bearings are fragile things so treat with utmost respect. Drop one onto the floor and it is scrap metal. BTDT.
 
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I was confused why there were no angled lines < on the bearings in my spindle and came across this today:

9.8 Duplex arrangement codes of duplex angular contact ball bearings

Duplex angular contact ball bearings have a product number and duplex arrangement code on the side of the bearing (see Fig. 9.11). Duplex angular contact ball bearings of 3 rows or more have a “<” mark on the outside diameter surface of the bearing. Always ensure that the “<” mark is aligned when assembling them (see Fig. 9.12). Additionally, face-to-face duplex (DF) and back-to-back duplex (DB) angular contact ball bearings do not have the “<” mark , so use the duplex arrangement code to match them.

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Source: https://www.ntnglobal.com/en/products/catalog/pdf/2260E-02.pdf

That's a pretty clever dual-purpose use the product code.
 
You may find pulling off bearing to be a one-way trip - it's going to be difficult to do (unless they're a very light press fit) without putting stress through the balls into the inner races. If you do that, there's a risk of brinelling the balls/races, and then it's replacement time...
 
From what I gather and the feedback here it sounds like the most pragmatic approach to this is to replace the bearings. I think there are too many unknowns with the current spindle given it’s already in a bad state.
 
From what I gather and the feedback here it sounds like the most pragmatic approach to this is to replace the bearings. I think there are too many unknowns with the current spindle given it’s already in a bad state.

True, but you DEFINITELY want to observe/note how they're currently arranged, because you want to find the root problem so you don't repeat it.
 
Pulling a precision bearing and reusing it is just this side of impossible.
Even if it has never been run and you made a mistake putting it together.
The bearing is now trash can stuff. There are no second chances on this assembly procedure.
This is why the whole make sure everything right and the crazy time and care taken.
 
Spindle history:
...I do not own the original machine. I'm messing with it for learning purposes and plan to use it for a future machine (if possible).I purchased it about 10 years ago and it sat until now. Judging from what I've seen it's been serviced and rebalanced before.
Since you do not "need" it for a down machine I would try to carefully remove the bearings. Play around with putting the whole thing in the freezer and then a hot piece of metal with a hole in it to slide down the spindle to warm the bearing may relax the press fit enough to get it off with minimal damage. Then you can really asses how it was put together and maybe you can put it together correctly just to see that it does remove the play.
It will for sure be a learning experience and you probably wont make it worse, after all it is not useable now...
 
True, but you DEFINITELY want to observe/note how they're currently arranged, because you want to find the root problem so you don't repeat it.

Replying to myself here - along with checking the bearing arrangement, get a total stack height of the bearings as currently assembled, and try to get a matching measurement for the depth of the spindle housing including whatever the cap projection is.

Obviously, you want some small amount of compression on the stack before the cap is fully tight, perhaps a .005" difference for the cap before it bottoms on the housing. Be sure nothing else could be the problem before you try removing these bearings.
 
I have often found that someone figured that the inner or outer spacer needed adjusting. Not!! Check the lengths. Every Bridgeport I had that came in with a chatter problem was either a mis adjusted nose nut or incorrect length spacers. Never did change a bearing.
 
Apparently Im late to the party and didnt read every reply 100% through but I can probably answer your questions pretty quickly.

First, the axial play is NOT supposed to be there. Could be caused by a few things (failed bearings, spacer offfset issue, loose nut, incorrect arrangement) but either way its almost certainly coming apart for a rebuild.

Correct arrangement for this spindle is tandem back to back (or dbb) in the front, and back to back (or db) in the rear.

Some notes,

Those bearings are almost certainly shot anyway, so no worries about removing them understanding that if you want this to work youre going to have to throw some money at it.

If you are to attempt this repair yourself, make sure you get the right precision bearings and are comfortable setting preload and capture correctly.
PS to all, you cant always trust the > on the od of a bearing, different bearing manufacturers use it different ways so it can trip you up. Looking at a bearing and understanding how it works with the entire arrangement and forces applied is the only real way to know (or a print). Plenty of times I see spindles come in rebuilt incorrectly, without knowing how it should work you would perpetuate the problem.
 
I got roasted by the wife.
I was telling her how I would need to do maintenance on the spindle in a clean environment and she said "So where are you going to do it"? 💀
 
I managed to get the old bearings off with a shop press and greased up my new bearings with Kluber Isoflex NB 52. I think I need more grease still but there’s great adhesion to the ball bearings so I feel pretty good about that.

What I’m wondering now is if I need to stone this spindle. It feels smooth to the touch but there are obviously marks from pressing the bearings off.

Side note: the bottom most old bearing was severely worn (inside race spins faster than the balls that contact it) so I think the idea that this spindle not being able to get any worse was correct.
 

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I managed to get the old bearings off with a shop press and greased up my new bearings with Kluber Isoflex NB 52. I think I need more grease still but there’s great adhesion to the ball bearings so I feel pretty good about that.

What I’m wondering now is if I need to stone this spindle. It feels smooth to the touch but there are obviously marks from pressing the bearings off.

Side note: the bottom most old bearing was severely worn (inside race spins faster than the balls that contact it) so I think the idea that this spindle not being able to get any worse was correct.
Stoning probably won't hurt it if you focus on just the axial grooves.The ones I see in your picture are normal any time you put a bearing race on a shaft and take it off. Those are micro grooves, they won't affect the fit. If you see any noticeable gouges, then stone those.

BTW a spindle like this can still work even if you drastically change the bearing setup, such as only using a single set of matched bearings with a bearing locknut holding them together, with a ground spacer disk between them. You can even just put a very thin shim between the old worn bearings so that the nut itself provides the preload.....won't last 10,000 hours, but its cheap and easy, and allows you to turn old worn bearings into heavy preload bearings that generate a bit more heat but are very rigid.
 








 
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