Thanks for the technical info, Ned. Those numbers help to put things into
perspective.

I think those numbers were intended to apply to quality bearings, and not
many varieties of the dirt-cheap versions.

I suppose that a portion of the $200 bearing price would be for individual
human inspection and selection of the bearing assemblies, and possibly
related to a certain number of rejects that don't make the grade.

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


"Ned Simmons" wrote in message
...
On Sun, 21 Dec 2008 23:38:22 -0500, "Wild_Bill"
wrote:

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".

A $6 6001 (12 x 28mm) bearing is rated for 26KRPM grease lubed and 32K
in oil. Oil mist or oil spot lube will probably push that to 45K. But
the devil is in the details of the spindle's construction at those
speeds. What you get with a $200 bearing is not necessarily higher
speed, but closer tolerances on the bearing's dimensions and running
accuracy.

--
Ned Simmons