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

I figured that now wasn't the right time to try and redesign the spindle so I went ahead with what I had. I guess the ball bearing might add some extra radial load capacity or something. Maybe not, whatever.

With the spindle reassembled I am still measuring .001" runout. But now it is repeatable to the same location on the spindle (marked in the image with white paint) as opposed to before when it was random. I'm guessing the R8 taper was ground off center from the manufacturer, or maybe ground in place with the original bearings installed.
IMG_20240922_131621.jpg

Do I have any recourse here besides try to re-grind the taper? If that is the way, anyone have suggestions on how to accomplish it? At this point it may just be a "live with it" type thing and accept it as a limitation of this machine.
 
That sounds like progress. Regrinding or turning is pretty much the only way to take out the runout. I’ve seen posts of people regrinding the spindle in place, and others that take the quill out and rebore the taper on a lathe. I would run the spindle a bit to make sure everything is fine before doing anything to the taper.

Wells-Index regrinds tapers, you send in your assembled quill and they regrind in the existing bearings. There are plenty of spindle shops that do the same thing, you might even run into one that is familiar with that spindle and can answer the question on what bearings should be in there.

www.wells-index.com

Wells-Index Milling Machines

www.wells-index.com www.wells-index.com
 
For anyone curious about having their taper reground, I did end up calling Wells-Index. Their price for a taper re-grind is $236 at present. Honestly, not terrible, however I'm sure the shipping from Utah to Michigan and back won't be pleasant! I am still looking into some other options. Maybe I can at least find one that's a little closer to reduce my shipping cost.

I live in a major enough city that there are two shops in my area that specialize in grinding. One turned me away. The other wasn't a flat out no but told me he would have to come up with a way to turn the spindle while holding the quill in his chuck, and would let me know if he came up with anything. I'll consider that a soft no :confused:.

In theory I think it could be done on a lathe by clamping the quill in a steady rest and driving the spindle with the lathe chuck, but I'm sure mileage and accuracy would vary with that approach.

Wells-Index has given me the most positive response of my lines of inquiry so far. If nothing else pans out, I will have to save up my pennies and send it off to them.

I also watched some videos on tilting the mill head and rigging up a die grinder. Honestly, it's a pretty appealing option. I'm sure I could do something similar with my lathe whenever I get it up and running again, since my spindle is so easy to remove. I think for the moment the runout is liveable as long as I don't need to drill/ream any small diameter holes.
 
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That’s a better price than I thought it would be. The only spindle shops I know of are out here on the east coast, so that won’t help you. I wouldn’t send it to any local machine shop, you want someone experienced with spindle tapers so that they get it right.

There was a post showing someone regrinding the taper on their lathe, I can’t find it now. They had the quill held by the steady rest and the splined section in the chuck and turning it as it was ground with a toolpost grinder. If you search here, you might be able to find it.
 
Ischgl99 said:
There was a post showing someone regrinding the taper on their lathe, I can’t find it now. They had the quill held by the steady rest and the splined section in the chuck and turning it as it was ground with a toolpost grinder. If you search here, you might be able to find it.
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I will search around, as this is exactly what I had in mind. I think it would be much easier to get the compound set to the correct angle than try to get the mill head angled correctly.

I think that's the conclusion to our story for the moment, at least until I also get the spindle bearings for my lathe replaced and a VFD set up for it so that I can rig up a tool post grinder to try and correct my taper. I like the idea of sending it off to Wells-Index, but frankly it would be hard to cough up the money, and I have some personal doubts about this machine being worth it altogether.
 
If you decide to do it yourself, buy a good quality solid r8 taper tool to use as a master to check to make sure you have the angle correct. Don't rely on a collet.
 
I wanted to give one last small update on this and thank everyone for their contributions to the thread, I put the spindle back in the machine and ran the bearings in today. Starting at the lowest speed available and running the machine in 20 minute intervals before stepping up in speed. At top speed (~2,000 RPM) at the end of the run in, the spindle temperature was stable at 125° F, measured inside the spindle taper with an infrared thermometer.

It's running smoothly and quietly, I believe the peak temperature I observed is acceptable. The bearings I chose also seem accurate as the runout continues to be repeatable with the spindle rotation.

It's not a perfect outcome, but it's better than it was. Some videos and resources online have given me some inspiration to regrind the taper to clean up the last little bit of runout, so I think that's what I'll be cooking up next. I'll be sure to make a new thread and show off that process as well when I work out my exact plan of attack.
 
My mill has .0015” runout and still works. It needs to be improved, but you can still get things done until you are in a position to correct it.
 
Four important issues the video totally or almost totally ignored and did not explain or clarify at all.

1) Stan showed us the DTI indicated runout of only one circular element of the mill spindle taper. I would want to see at least two, widely spaced along the taper, to get any sense of whether the axis of the taper is parallel to the spindle axis of rotation or whether the taper axis is skewed (wobble). The reason for wanting to know has to do with understanding the existing relationship between the taper and the .95" ID precision collet registration feature further back in (normally up) the spindle. See 2) below.

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).

3) Stan said one short sentence about positioning the height of the grinder spindle equal to the height mill spindle. That is totally inadequate. ANY error in that height and/or angle will result in the stone cutting a different angle taper than intended. The AXIS of the grinder spindle MUST lie in a plane parallel to the table travel AND containing the rotating axis (bearing influence) of the mill spindle.

4) After the grind, Stan showed us tool runout very close (.2"?) to the collet nose. That's not very useful because we don't usually cut chips that close to the collet. What is the runout at 1"? At 2" At 3"? At 4"? And, for those who use a 1/2" keyless chuck to hold twist drills, how about 6" and 8" away from the collet nose.

I like Stan in general. After watching that video, I will be much more wary of his "precision" work.
EDIT: Out of curiosity, I went to BarZ Youtube channel to see how old that video is. It's 8 years old. Stan started making machining videos about 10 years ago. We can all learn a lot in 8 years.

Grind away baby. Tune-up that spindle. Make it better.
 
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