: I'm inheriting some tools from my grandfather's shop. Most noteably
: a block plain and a sliding combination square. They both have
: some rust and I doubt are in full working order (i.e. I wonder
: if the sliding square actually slides). I don't have them in
: hand yet, but I wanted to get a feel for what it takes to
: restore them to working order (even if they're not pretty).

I'll second using brass brushes, it's a softer metal than the steel the tools are made with so won't take off what you don't want removed. I'd first look at naval jelly, works pretty well at removing rust. Downside is it needs to be washed off with water, so you need to displace the water when you're done, I use acetone for that. Heating the steel surfaces can also help to drive off any moisture.

Bill H.