Info/plans for homemade spot welder?

[jabce85]

I have heard from many people that building a small spot welder at home is not very difficult at all, but after doing a little research, I have only come up with one lead:

http://www.5bears.com/welder.htm

I was just wondering if anyone here has either built one of these, or has any info on building one. Anything would be greatly appreciated! Thank you very much for reading!

[Anthony]

Ask Rossco (member here), he seems to know a lot what he's talking about.

[pezman]

That 5bears link is cool. I'm gonna look around work for a suitable transformer. I'll just use a little computer that I have lying around for the timer ...

[Rossco]

Hey, thanx for the PM. I had missed this.
Thanx for the vote of confidence Anthony!
The best spot welder that i have seen lately runs of 12V, standard automotive battery. I didnt look at it too closely, as it was expencive, but did think about making one myself. I will have a beter look at it and let you know.
My parts shop that stocks them, will know exacly what im up too, but i will offer them a batch of mine as a cheaper alternative for the trouble! For a small price that is.
Let me know if youve come up with anything in the mean time!

What are you hoping to do with it BTW?
I was thinking that it would be good for tacking before welding, but decided that it wasnt worth the effort.
I dont see tooooo many issues in making a "seam" spot welder tho, with rollers and the like. Now that would be handy, and make a great job of a jet.

Rossco

[jabce85]

I was planning on using it for welding the combustion chambers on a small turbo-jet engines.

I have been thinking about how I should go about making this. Most of the homebuilt spot welders I've seen have all been attached to a sheet of plywood, or something like that. I was wondering if I could make a custom box to hold all of the parts except for the actual welding arms? (To make it somewhat portable/out of the way.) I was looking around and found this: http://www.hobbyspotwelders.com/HS300A2.php. The only thing that I'm not so sure about is that I was planning on using a transformer and not a capacitor; so would a box idea still work for a transformer(size?)?

Another thing, I have found all the parts that I need, except for the transformer... and I'm not really sure where I can find one cheap. Any ideas? Thanks for the replies so far!

[El-Kablooey]

Hey dude, I built a spot welder using two old MOT's (microwave oven transformers) they are cheep!! just look at the dump or put the word out to friends that you want broken microwaves and you'll soon be flooded with the damn things.. just cut off the secondaries (the skinny wires) the easiest method is to use a bandsaw and cut them off flush with the core on one side, and find a piece of bar stock just small enough to fit through the holes in the core, use this to pound out the wires in one chunk.. if you don't have a bandsaw, a crosscut handsaw for cutting wood seems to beat a hacksaw for ripping through this soft copper.. wrap 2 wraps of 4 gauge wire in place if the secondaries on each MOT (try to preserve the original direction of wrapping) and wire them with the primaries in parallel and the secondaries in series, this should give you 4 volts, if not reverse the wiring of the secondaries.. you may be able to get away with one MOT and #6 wire but i try to go heavy duty.. I also built myself a pretty darn fine arc welder using 4 MOT's and a myriad of other electronics.... An unaltered MOT + the high voltage capacitor that came with it will also make a hell of an ignition device, only don't use a sparkplug, as I have found that they first light up like a X-mas light bulb then violently explode when subjected to such high currents :).. sparkplugs may be ok if you leave out the cap though..