I decided to make a cart for the 250 EX tig machine and my PP60. I tig welded the whole thing except for two small welds at the bottom that were done with the mig.
Didn't really have a plan, I just cobbled it up out of what I had on hand. Everything had been rusting outside for a year other than the sheet metal. The frame is 1x1x1/8 hot roll, the sheet is 14ga hot roll.
I tried making plug welds on the bottom shelf but they turned out looking like crap so I gave it another pass with the 7" 24 grit flap wheel. I just tacked the top every two inches, that worked much better for me.
I wanted to mount the Motor Guard M60 dryer to the frame but it didn't come with a bracket, so I cut two pieces of 1/4x3 hot roll, welded them together and then plasma cut the bracket and cleaned it up on the belt sander.
The dryer just sits in it and can be lifted out for service. The bottle brackets are made from the same 1/4x3 hot roll.
My welds range from OK to crap but I'm practicing. Poor eyesight is my biggest problem, getting old sucks.
I shot it with semi-flat black Rustoleum. The primer ran like water but it'll work.
The caster brackets were cut from two pieces of 1x4 cold roll, then cut in half on the horizontal band saw to make them about 1/2" thick and threaded 1/2x13 for the 5" ball bearing total lock casters.
I like casters on all four corners so I can move it in any direction. The cart doesn't go outside. The casters cost about $9 each and work great. http://www.ebay.com/itm/151428117977?_
I put them on everything that needs to roll in my shop.
I'm happy with it, it suits me.