I know there are some folks here that have considerable experience with high
speed parts and lubricating oils.
I anyone has recommendations for oils with properties suitable for high
speed bearings, I'd appreciate hearing them.

The spindle speeds in toolpost grinders can range from about 6k to 30k RPM.

I haven't taken them apart to see exactly what types of bearings are used in
the spindles, but I would expect them to be high precision ball bearing
assemblies. I've seen parts list prices of over $200 each for bearings with
ODs of about 1.25".

I presently have two brands, Themac 1/2 HP and Dumore 1/4 HP.

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WB
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metalworking projects
www.kwagmire.com/metal_proj.html