Spot welding

[metal-rx]

I'm very new to the spot welding world and am looking for some help. Hopefully, my questions won't sound too stupid. It appears to me that the spot weld only tends to make a weld directly between the electrodes. Is it possible to make a 1/2" long weld on a cylindrical piece of steel? To make my request more visual, say you had a piece of pipe 1" in diameter with a .150" wall. Then you would want to spot weld a 1/4" thick by 1/2" long piece of steel to it that has the same contour. Would it work if I was to make an electrode that mirrored the contours of both pieces? Thanks for the help. Kevin

[aametalmaster]

Sure its possible if you had a big enough machine. All kinds of products are welded between "platens" which are big copper plates with cutouts for the parts to set in before they are welded...Bob

[kcstott]

thats more like stud welding and depending on the strength you need I'd still say no.
Spot welding is not normally used on thick sections unless that thick section is not going to be subject to any real load. after that you are looking for some very specialized tools to do the job due to the power required to do it. that a lot of amps to get that to work
At an aircraft place i work in from time to time they have a very nice roll resistance welder that can take a four foot diameter sheet metal part and roll it with another and weld it together. it's for the cowling on jets if you want to know Goodrich aerospace Chula Vista
You would be better off silver brazing or welding it either tig or mig in a fixture.

[tacmig]

Unless you use a depressor rod getting an arc to cooperate through 1" pipe to deliver a strategic weld on your target area is going to be like welding with an open arc at best and the current required will probably deform your tube beyond recognition. If you can make a depressor rod which is simply a probe with a protected element pad of the opposing current (ground) you can probably pull off a "pulse type" weld. These rods are generally used in larger dia. pipe for affixing internal attachments. What is keeping you from mig or tig?

TacMig

[metal-rx]

I'm currently silver soldering the parts together. This works well, but I was researching for a stronger bond and a faster way to bond them. There is at times some pretty good pressure put against the joint and the silver solder will part. Tig welding has worked, but the cleanup in the tolerance area at the junction of the parts is critical. I recently was experimenting with the spot welder and welded the two parts together but only at the area directly between the electrodes. My next step will be to use this weld and also apply silver solder to the joint.

[metal-rx]

I should have mentioned above that I made an electrode that fit inside the pipe for the bottom of the weld. I assume that this would be the depressor rod you're speaking of?