SV15 Crankshaft Grinder Head Stock Bearings

I am working on an SV15 crankshaft grinder. I am not an experienced grinder.
I can just get my tolerances within 0.0002" and feel I should be able to accomplish this easier than I am.
I used 6208 ball bearings on the head and tail stock (many owners do). I am now questioning that. The inner races are pre-loaded on each other with a nut causing a significant side load on the bearings. From what I understand the only advantage to going to a 7208B-2RS angular contact bearing would be longer life. But I would have also thought that there would have also been some accuracy which may explain my slight run-out concern.

What do you think?

6208 bearings can come in several different grades, you could contact your bearing house for specs. ABEC specs 1 through 7.
Use only the best quality 6208 DEEP groove bearings, They can handle a Dynamic load of around 7,300 lb and a Static load of around 4,300 and live at insane high speeds in an oil bath and slower in a grease environment.

I used to rebuild Van Norman Crank shaft grinders and when I wanted it I would tweak the spindles /bearings close to zero. I would drill and tap 8/32 holes around the perimeter of the star nut between the notches. After you get it as close as you can then to tighten the set screws in the tapped holes to tweak the bearing. Once you get it, then remove them 1 at a time and put some blue loc-tite on them. I only used the precision bearing though.

Another thing I did once got the bearings done, I assembled the cross slide on. I would build a stand and set the head slide side up and mount a mag base and indicator .0001" on the head. Then using a gage block ( above the dovetails)and scraped the cross slide ways so it was zero on all the flats. Then match fit the slide. The problem you get by using precision bearings you get a multiplication of errors.

One thing i have found is the weight of the crank has a big effect on how this all works. A storm vulcan with chucks is a poor design for any precision, if you place a medium diesel crank in one you need to be real fluent in Kentucky windage. I know ive owned them and had professional techs try to improve it. Now take the chucks of the same grinder put centers in and now it works.
berco has the chucks figured out as long as the rotary mechanics are set right and in good shape. Have had them rechromed and ground for .0000 to -.0001 for the needle bearing clearance. Any more than that and it will not grind round without kw. But if your grinding on chucks it only ever going to be as good as the chucks. And good grinder chucks are$$$$$$.


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Richard King said:

Another thing I did once got the bearings done, I assembled the cross slide on. I would build a stand and set the head slide side up and mount a mag base and indicator .0001" on the head. Then using a gage block ( above the dovetails)and scraped the cross slide ways so it was zero on all the flats. Then match fit the slide. The problem you get by using precision bearings you get a multiplication of errors.

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can you explain that, please? star nut = spindle nut?