How Should These Spindle Bearings Be Lubricated? Also, What Bearings to Buy?

[ChandlerJPerry]

2) An R8 collet has a .95" OD cylindrical feature (an inch long) on the opposite end (from the taper) of the collet. That is a precision diameter and mates with a precision ID in the spindle. The .95" diameter is part of the alignment system for the collet in the spindle. Stan simply said he wasn't going to grind it. He didn't say what the runout condition of the .95" diameter was or if he even measured the runout or diameter. Trying to fix R8 socket runout without understanding the condition of the .95" ID is foolish in the extreme. If the .95" diameter is not coaxial with the taper, the collet will bind and/or the collet will not be coaxial with the spindle axis of rotation (collet wobble).

More on the theory side of things, what could one use to grind that feature? Using the same methodology that is. I think most die grinders would be too large to fit, even those that are extended reach.

It would also be pretty difficult to measure, needing a tenths indicator with a very long probe, something I'm guessing most people don't have (myself included!). All that to say that I'm not surprised I've yet to see the R8 taper ID mentioned in any DIY grinding videos.

 

[extropic]

More on the theory side of things, what could one use to grind that feature? Using the same methodology that is. I think most die grinders would be too large to fit, even those that are extended reach.

Real tool post grinders, have extended reach spindles available, that could reach it. The grinding stone (mounted point) could easily be .9" OD so the supporting spindle assembly could about the same (substantial).

However, reaching it is not the end of the issue. If the .95" ID has unpleasant runout (relative to the rotational axis of the spindle) and you grind it true, now it is probably bigger than the design allows. What are you going to do about that? Grind it big enough to press/Loctite in a hardened sleeve and grind the sleeve ID to spec? How hard is the sleeve? Hard enough to wear well but not so hard you can't drill and ream for reinstallation of the anti-rotation pin. The anti-rotation pin/sleeve compatibility is not an issue if your anti-rotation pin isn't located within the length of the .95" ID feature. See the next paragraph.

Let's not forget that the R8 spindle design includes a pin that protrudes into the .95" ID and prevents rotation of the collet vs the spindle during installation and removal. Many operators are not proficient in the accommodation of that design feature which leads to collet/pin damage, operator frustration, irrational behavior and the ill advised removal (path of least resistance) of the pin. But I digress . . .

I keep referring to the precision diameter as .95". That is because I don't know the the exact dimensions or tolerances approved by the responsible engineer(s) for either the collet design or the spindle taper design. I don't know if there is an actual published and controlled "Standard" for R8. I suppose it could be a proprietary standard created and closely held by Bridgeport (now Hardinge). I don't intend to do the research needed to sweep all the opinions out of the way and get to the actual design authority approved dimensions. Someone trying to fix their spindle might want to do the research, or they might self-define their own design (or take somebody else's opinion).

 

[Optic Eyes]

Lot of good advice, clean everything, look for wear on balls and races, put same bearings in as the manufacturer installed. Lubricate them with Mobile sch32 grease initially, do not pack like it's a car wheel bearing, regularly oil with Mobile medium way lube, should last for years, milling machines run very well with class 5 bearings.