Lubing ballscrews?

[mayhugh1]

I have a CNC mill that has a one-shot oiling system that, in addition to lubricating the ways, lubricates the ballscrews; and everything protected by waycovers. I also have a CNC lathe which has protected ballscrews but no provision for oiling. My question is "Are ball screws designed to lubricated?" It seems to me they are essentially bearings and should receive some type of lube, but I see so many small machines running with no provision for lubrication.

[NC Cams]

Lubed for life bearings and/or ball screws or nuts are lubed with grease. Grease is basically oil with a thickening agent - akin to industrial gravy. Low viscosity grease (NLGI #1 or so) is effectively really thick oil - it is almost like real cold maple syrup or maybe a bit thinner.

The ball nuts/screws MUST be lubed as metal to metal contact w/o lube will result in early/premature ball or raceway spalling. Whether it is vial lube for life or replenishment after the fact, there has to be lube applied at some point in the service lift of the screw - otherwise, it will be a very short service life.

A common grease for ball nuts in ball screws is Shell Alvanai #2. A grease by Exxon called Beacon 32 can be used but it is REALLY light stuff - pretty sure it is NLGI 1 or 1.5 in viscosity. Low viscosity lubes are better for low friction. Higher viscosity lubes tend to provide better oil films, especially under oscillatory motion situations.

The advantage of lube for life anything is cleanliness. The disadvantage is that once/if the lube for life gets contaminated, you have lapping compound and accelerated wear.