[big gear head]

You have probably talked about this several times before, so if you have links to other posts I'd like to see them. I have to make stainless trays and boxes at work sometimes. I notch the corners and use a box and pan brake to bend the sides. I have to weld the corners so that they don't leak. I've tried using a gas lens with a number 15 cup on the back side of the weld to shield it (2 flow meters and separate lines), but that doesn't work too well. I've been clamping an aluminum block to the back side and that seems to work better. Is there a better way to shield the back side of the weld?

[AndersK]

Drill a lot of small holes along the edge of the aluminum block. Cross drill to connect all holes, connect your purge line there.

I think Jody showed a block like that in one of his recent videos.

[Rick_H]

I use a piece of alum or bronze clamped to the back all the time in those cases with no sugaring on the backside. If you need the purge on the back the method mentioned above works well.

Are you fusing or adding filler metal, either method works. Make sure the joint is tight, I use a 1/16" tung, #8 ga lens, foot pedal max of 60amps, some times I'll pulse as well, 75% peak, 25% background, 10pps (max my older syncro 350 will do), 16g 304L

[Braehill]

In addition to what has already been suggested, you can clamp small angles about an inch on either side of the face side of the joint to keep the cover gas in the area longer to aid in cooling it. Kind of makes it like a fillet joint as far as coverage goes instead of letting the gas travel away it traps it there. The faster the stainless gets through it's critical temp the less chance of sugaring.

You can make a specific purge box for it if it's a joint that you do often. Make a closed box out of copper and either use perforated or drill holes in the corner facing the joint and fill it with s/s wool.

If you have a box and pan brake you could also make a dust pan purge dam to clamp in the corner. This is a square piece placed into the corner with sides that go down to meet the base of the pan trapping the gas in the corner. Think of a diamond shaped dust pan. Probably easier to make than to explain in writing, not even sure if this makes sense.

Len

[big gear head]

Lots of good ideas. Thanks a lot. I am adding filler. I do understand what you mean by the dust pan purge dam. It seems like something that would work well in some other situations that I have to deal with.