I usually have them all seprate on diff hooks saves a world of trouble. I have a perfect example I was making a forward facing plenum for my 20 and I cut it out using a 1 mm disk acidently put one I used for steel then when I went to weld it had all sorts of trouble with inclusions had to back grind everything wasn't happy tho so I tossed it. Now all disks are kept separate and tidy. Also you may find it easier to weld alloy of you wipe it down with thinners, cleans the surface much better