Surface Plate

 I've been interested in getting into hand scraping, for some of the small mechanical things I make.  I don't have access to a surface grinder, but scraping will let you get things flat down to 0.0001 inch if you have patience and persistence.  This makes it so parts mate nicely and move smoothly.  To make really flat parts you need a reference flat surface, often called a surface plate.

I'd been hunting around the interwebs for a granite surface plate.  There are cheap ones from China that would probably do the job, but I really prefer USA made tools when possible.  I happened to find that Rock of Ages, a granite quarry about half an hour from my house, made surface plates.  I gave them a call and ordered a 12"x12"x4" surface plate with 0.0001 accuracy.  That means no point (on the top side of the plate only) is higher or lower than any other point by more than 1 ten-thousandth of an inch!

 

I don't really need this level of accuracy, but it didn't cost that much more than the next level down.  I'm super excited that the granite is local and so is the work that was done to make it flat.