Tool post grinder questions

[BenW]

Howdy. I'm designing a simple toolpost grinder based on 2 tapered roller bearings I have. My main question is what type of seal to choose and, related to that, what rpm I should shoot for. The bearings are skf 32004 X (wheel bearings I think) And I'm planning on using an er straight shank chuck as the spindle body. Are the bearings good enough/ the right-ish size for this application. It's of course a hobbyist-level grinder and I don't plan on pushing it too hard/running dremel bits at 30k rpm. Thanks for your time.

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[Bob Korves]

Keep in mind that grinding wants surface speeds of about 5,500 to 6,000 surface feet per minute. Unless you are making a BIG tool post grinder for doing O.D. work only on a BIG lathe, it will need to reach some high spindle speeds, too high for the bearings you have in mind. My Dumore 44-011 tool post grinder has spindle speeds from 6,600 to 38,500 rpm. It fits nicely with my 13x40 lathe.
https://www.dumoretools.com/tool-post-grinders
https://www.dumoretools.com/tool-post-grinders/series-44

 

[benmychree]

You should use angular contact ball bearings with non metallic separators for a grinding spindle, and a precision grade of bearing at that; definitely not tapered roller bearings. Seals are generally not used on grinding spindles, just a laberinth clearance fit with the housing.

 

[NortonDommi]

The following book from SKF has information on spindle bearings starting page 7.

 

[john.k]

Depends on how much you want to spend..............from $10 for a SKF ball to $1000 for a precision spindle .............As mentioned ,dont use taper rollers.....they will have runout in every direction in standard grade................I have often found SKF,Koyo,Naachi,good quality (non Chinese) balls have near zero measurable runout.........endload with a light spring ,or manually adjust ,if you prefer.