doublet wrote:...I don't see any reference to a 510R on the shopsmith site. What is the difference between a 510 and a 510R?
You got your first Q answered. As for the "R" after the 510: Do knot take this as gospel, but as I understand it, it was either one or the other of the following: 1) When SS sent out an upgrade, they included a sticker that an owner could apply to the upgraded Mark V. The sticker had the "R" which referred to the unit being upgraded; or 2) The headstock was rebuilt and the "R" designates that. There are posts on this forum somewhere discussing this.