How to remove weld beads flush?

[Daedalus]

I have a steel building for a garage. The garage door frame is made from square channels (sheet metal with internal ribs screwed together to make a box frame). The sheet is quite thin (~.054). The original owner welded gate hinges to the frame for the existing barn doors. I'm installing a roll up door and need to remove the hinges. Since the sheet metal is so thin, I'm worried about cutting through the sheet when removing the hinges and beads with an angle grinder.

So how do I grind the weld beads off flush without getting into the sheet metal they're attached to? Is there a special wheel that's good for this kind of thing?

 

[alwaysFlOoReD]

I'd probably use .045 cutting disc on my 4.5"/5" grinder and cut the hinge side of the weld. Work my way thru slowly until just a hairs worth of metal is left and then pry up carefully. After removing the majority of the hinge I would use a regular grinding disc and work my way down to the original metal, doing final cleanup with a flap disc.

Richard

 

[BD1]

As stated above. If you do go through just use metal bondo to patch

 

[Duker]

I have a steel building for a garage. The garage door frame is made from square channels (sheet metal with internal ribs screwed together to make a box frame). The sheet is quite thin (~.054). The original owner welded gate hinges to the frame for the existing barn doors. I'm installing a roll up door and need to remove the hinges. Since the sheet metal is so thin, I'm worried about cutting through the sheet when removing the hinges and beads with an angle grinder.

So how do I grind the weld beads off flush without getting into the sheet metal they're attached to? Is there a special wheel that's good for this kind of thing?

I usually remove the bulk of the bead or metal with a grinding disk then switch to a 40/60 grit flap wheel disc which gives me better control and is easier for me to level out.

 

[Daedalus]

Re: bondo, it's not a cosmetic concern. The hinges run the full width of the inside jamb, and I'm afraid of damaging the sheet metal and thus compromising the overall strength of the channels. Thanks everyone for the replies. I'll give the flap disks a try after the grinding wheel.

 

[Bobhdus]

Sometimes grinding a weld on thin material you can manipulate the grind wheel so it's only touching the weld (don't overheat it!) and not the base material. By going at a 45 degree angle with the wheel. Once the weld gets ground down and is close to the parent material it will sometimes glow red and almost peel off. At least this is the case with a mig weld as the penetration is not that great and the dilution is worst with mig than other processes.

 

[jtex]

Grind down, then switch to a file. Hand filing will give you the control you need.

 

[Heavymetalmechanic]

I have had good luck using a cutoff wheel on my angle grinder to remove the hinge/bracket/etc followed by my 90* air die grinder with 2" roloc disks to remove what's left of the weld. Swapping out for less coarse disks as I get closer to the panel for better control.

 

[fourjeepin]

For jobs like this, I use the sanding discs on my 4-1/2" grinder. I think they give better control over a grinding disc and I have had more success with them than flap discs.