[Mikbul]

Page 56 of "Timken Super Precision Bearings for Machine tool applications" says:

The use of “low-torque” greases (or synthetic greases) can be
considered for rib speeds over 13 m/s (2560 fpm), up to maximum
of 25 m/s (4920 fpm). Experience has shown that stabilized
temperatures, around 15° C to 20° C (27° F to 36° F) above ambient,
can be obtained at the maximum permissible speed.

....

When using synthetic greases, the limiting factor is the "lubrication
for life” concept (without re-greasing). Depending on load and
speed conditions, the grease life will typically be limited to 5000
to 8000 hours.

As I mentioned earlier, when new spindle arrives I will put headstock apart and document it's condition if anyone is interested.

Ed

I'm not going to argue over oil or grease, one factor to consider is shop and spindle temperature, you would have to monitor that very closely with grease if you have a cold shop that you warm up. I brought my spindle in last night and it took two hours to warm to room temp, and that's out of the headstock. When I warmed the shop in the past I waited until things warmed up then ran the lathe at 45rpm's for twenty minutes to get the oil and bearings warm. When I get a new spindle installed I'm going to check spindle temp, I might even run a heat gun on low for a bit trough the center of the spindle then wait until it stabilizes before proceeding. This frigid weather I've closed the shop down until the temps come up to keep the bill down.