Hope this isn't a highjack, but here's a crazy idea on surface plates.
Some folks find an old tombstone and use the back for a surface plate. But--warning
--they weigh a ton! Many are dead flat because the polishing process is essentially a form of lapping. But you do
have to check carefully, as some are not
Mine came out of a letter-press print shop when the printer absconded while owing me money. He got the granite really cheap because someone traded in the family tombstone for a newer, more stylish, model. (Honest! I'm not making this up.) I think he paid $34, if my memory is correct. Of course, that piece of granite cost me more than a fancy surface plate, since the scoundrel owed me several K. (I'm not a loan shark; the debt came with a business I bought and later sold.)
Moral of the story: Some guys smarter than me can find bargains that I wouldn't have thought of. Shop you local monument company? Just check carefully.
My apologies. Let's get back to the thread!