These were actually machine bases for pick-and-place manufacturing intended for a silicon wafer manufacturer. The client bailed on the order when the machines were partially complete, so I'm marketing them as surface plates. What you do with them is within the limits of your imagination. They have not been used and only shipped twice. I have the certificate for one plate, and they were all made to identical specifications. The plates were held to a tolerance of .0005". I cannot find a definition anywhere for a plate of this size, so the best I can do is place it between grades "A" and "B." The largest deviation in the certificate, regardless of the tolerance, is a little over .000070" (seventy millionths), so they're of very high quality. If you want one certified, that can be arranged, but that will be reflected in the price.

Each unit consists of:
(1) granite surface plate, 50" x 50" x 8" thick, manufactured by Dover Instrument Corporation of Westover, MA. Each surface plate has (225) inserts with 1/4-20 U.N.C. tapped holes. Use them for hard stops, hold downs, etc. There are also large (about 3 1/2" in diameter) holes at the back of each plate which were for pneumatic lines and wires.

(1) machine base, manufactured by Dover Instrument Corp. All have wheels for mobility and adjustable feet which are lowered into place when you have the unit in place and are ready to level it. All are anti-vibratory. Some bases have extras, such as air accumulators, relays, air manifolds, unions, fittings, etc. If those are of use to you, they're a bonus.

(2) gantry rails, 46" long, made of granite, with hardened-steel inserts which were to be bearing surfaces for the gantry systems. The granite rails were made with a tolerance of .0001", and the largest deviation I can find in a certificate is about .0000070", just like the surface plates. If you don't plan to use the gantry system, these are excellent straight edges, especially if you're into scraping machine ways.

(1) gantry bearing plate, made of 2024-T351 aluminum. These were to span between the granite rails and hold the work head. They were manufactured to a tolerance of .005", but the certificate shows them to be mostly within .0002" of the established data. The largest deviation of a datum is .002" of datum "B" in parallelism to itself.

For comparison, a Starrett grade "B" surface plate, measuring 60" x 36" x 8" sells for over $3,000 through MSC. That's the PLATE ONLY with a surface area of less than 2,200 sq. in. These plates, removing the surface area lost for the clearance holes, have a usable surface area of over 2,400 sq. in. (that's if you remove the gantry supports). That's a plate with more usable surface area, several tapped inserts, two granite straight edges, and a moveable, leveling, anti-vibratory base for less!

This machine is listed for sale by located in Kempton, Pennsylvania