Is your arbor a weldon shank? My 3/4" arbor did have a flat. As I mentioned earlier I wanted to save that arbor so I didn't want to modify it to be able to hold it better. Otherwise I would have machined two large flats on it or cut off most of it then drill & bore.My criterion is the same way. I just use it with the chewed up straight 3/4” arbor it has. Wanted to change to r8 but can’t disassembly. Doesn’t really matter so it’s low on my list. It’d be different if I couldn’t use it as is for sure.
This ^^^How are you going to hold the arbor like that?
I think you might have better luck holding onto the arbor in the vise like I did. I used the mill vise cause I only have a light duty bench vise that's mounted on a woodworking bench with casters.Like this in the vise.