Leveling pads - steel or rubber?

All,

I am finally getting around to setting up my Yamaguchi vertical CNC mill. It has 38mm or 40mm leveling screws, but did not come with any pads. My Mazak lathe came with steel pads that the previous owner made themselves because the leveling screws were jack hammering their way into the concrete. I always had the idea that it should be on rubber pads. What are your guys' thoughts on steel versus rubber? The mill is the same basic model as the one in the link below.

Yamaguchi Vertical Machining Center

Thanks,
Aaron

Aaronh

Steel, they should of had cast or steel foot pad with the original machine, the machine would of never had the jack screws straight onto the concrete when it was new, someone messed up, being an older machine they most likely got lost by who ever moved it

Steel.

Steel of a large enough footprint to reduce the pressure so it won't jackhammer in to the concrete.

Steel it is. Thanks for the info guys!