I have a good 7" grinder, two 4-1/2" grinders (the el cleapo from Harbor
Freight), and a nice 4" Mikita. The 7" grinder with a disk will take off
way more metal than the 4". If you want even more serious metal removal,
use a grinding stone (be careful to get an appropriate guard, when a
stone blows up it gets messy!)

Assuming that you have a high interest in cosmetics and require flat
weld areas, I suggest:
-Weld prep with a fairly deep 'V' grove, gives you good pentration,
keeps your weld bead down flat. This can be done with a grinder (lay a
whole pile of parts with the edges raised on a 2x4 and do them in
quantity) but a 2" vertical belt sander is the best way.
-Practice your weld technique to get good looking welds on the underside
that don't need any touchup, minimal bead on the outside that need to be
ground.
-Use a 7" grinder with a disk to knock down weld bead.
-Use a 4" or 4-1/2" with as sanding disk to clean and polish the
surface. These grinders are cheap, have one loaded with 40 grit paper,
another with 60 or even 80 grit. Use a cube tap and have all of them
live at one time.

Emmo wrote:
I mig weld square and rectangular tubing to make furniture. I use a 4 1/2"
grinder to grind down the welds. I think I am spending more time grinding
than welding. I am wondering if getting a 7" grinder would make this go any
faster? Thanx!

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"All it took was all I had..."