Hmm, I made this unit from copying Rob Frink"s KMG (Knife Makers Grinder)
You really don't need much weld, i.e. "all around". Too much weld will cause the parts to deflect from their original location. What you need is "good weld" that being penetration and minimal undercut
I used springs from my cycle (always knew I'd use those old springs for something

). The tracking spring is from an old clutch basket, and the tensioning spring is from the front end of an old Harley. I really overdid it with the tensioning spring though.
All wheels, bearings, and platen mounting plate were bought from Rob Frink
The square tube size is 2" and 1 1/2" for the tool arm. As the square tube is seamed, you have to gring a slot in the tooling arm.
This machine runs great, but is certainly not as soothe as the real KMG.
By the way I call mine an MMG (Mighty Mouse Grinder

)
Good luck with your project, it's not too difficult yea!