very cheap (read: free) bases for your next gantry project

I may have stumbled across a vast resource of nice ridid extremely
flat surface plates for those of you building cnc gantry mills.

1" thick 2.75 foot by 4.5 foot slate that is precision ground to .001
inches. You can get these from your local pool table dealer for free
because they come in matched sets of 3 (cut for transport from a
single piece that is precision ground). Sometimes one of the pieces
will break in shipment or something and the other 2 slates will be
stacked in a growing pile in a dusty corner of the pool table dealers
back room or thrown out back with the garbage (like my dealer does).
Most of these have lots of holes drilled around the perimeter that
could be used for bolting on linear THK rails or whatever. You could
also drill more holes fairly easily since the slate is only 1" thick
(which means it weighs about 120 pounds versus many hundreds of
pounds for a granite surface plate from enco.

Just an idea.

Rick