What are you using to apply the torque to the wrench?
This reminds me of what I use for stubborn set screws when disassembling Shopsmiths for restoration. On some of the Model 10's which are now around 70 years old and have set screws that may have not been moved in all those years and they can be stubborn. I use an Allen wrench socket and socket wrench for better torque. I have yet to find one I could not get out with the Allen wrench socket & wrench.
using the opening at the end of an adjustable wrench (mentioned in the Shopsmith 510 on line manual) to turn the allen wrench.
I have tried that technique also without success. I ended up with a spiral twisted Allen wrench. That is when I tried the Allen wrench socket.
Mark V 520 S/N 09-11-01 completely upgraded to Mark 7, with all SPT's & more.
Model 10ER S/N R64000 first one I restored on bench w/ Shopsmith metal ends & retractable casters. Has Speed Changer, Model 4E Jointer, Jig Saw with lamp, a complete set of original accessories & much more.
Model 10E S/N 1077 oldest one I have restored. On bench w/ Shopsmith metal ends & retractable casters.