A 5/8" radius chisel?
Moving on to the next project...I need to buy or make a tool. Let's see if I can explain it. For a number of not easy to explain reasons I need a chisel that matches the quarter round shape of a 5/8" radius hinge. I've seen lot's of squaring up tools that would take a round cornered mortise and make it a 90 degree corner but none that would create the 5/8" radius to start with.
As if you were creating the hinge mortise with chisels only, I want a special purpose chisel just to mark and deepen that 5/8" radius. Before routers, what did our grandfather's use?