Hi,
An acquaintance is giving away a milled Marble top (20" X 30"). We can use it as a measurement table for keeping gauges, etc (keep it on one of the tables).
Good for measurement prior to Lathe or CNC machining, aligning, and checking parts after machining.
It was at the top of a coffee table, it has a couple of faint water stains. No chips, dings or
cracks. Very heavy, so I will need a hand to move it.
Please let me know if interested.
The tools for validating the flatness of large surfaces are very special and expensive. I’d be very surprised if it was within 0.025” over that size, which isn’t very good. Proper surface plates are thick so they don’t sag, and wear is also a big issue. High precision surface plates will get lapped and calibrated at regular intervals by specialized outfits with a high accuracy inclinometer.
I do not think that this would be useful. It is not likely flat enough for any practical use. Small granite surface plates are actually very cheap… $50 range.