70 Amp MOT Stick Welder

[scorch]

Home made Microwave Oven Transformer (MOT) stick welder. I based my design on the welder by Randy Gross (Homemade 70-Amp Arc Welder). It looks like Randy's web site is gone now but my welder lives on. This welder is made from two transformers from old microwave ovens. The transformer secondary coils were rewound, to achieve welding voltage, with 10 AWG solid copper wire. I included a fan from one of the microwaves for cooling.

(EDIT: here is a link to an archive of the original AAA Welder web page that I used as a guide to construct this welder.
https://web.archive.org/web/20100411...com/70amp.html )


Input: 120V, 20 Amp
Open circuit voltage: 40 Volts
Welding current: 73 Amps
Rewound transformer secondary coils with 10 AWG solid copper wire.
Welds best with 5/64 welding rod

[kbalch]

Thanks scorch! I've added your Stick Welder to our Electrical category, as well as to your builder page: scorch's Homemade Tools. Your receipt:

Stick Welder by scorch

tags: welder

[DIYer]

Cool build! Thanks for the share.

[Altair]

Nice work scorch. Looks like I'll be scouring for old microwaves now.

Al

[kbalch]

This thread has been moved to the Must Read subforum. Congrats (and thanks) to scorch for making such a valuable contribution!

[piloon]

Cool build! Thanks for the share.

I also made a DIY welder some years ago.
The transformer that I found was easy to disassemble and the primary had 88 turns so I guessed that about 50 or so would do for the welding side.
I used 1/4 " copper tubing to wind my secondary 'welding side' .
I then poured varathane varnish to isolate the secondary.
Surprise! It worked just great.
From the rods that I used I determined that I was developing as much as the 5/16 rods demanded.
Made many DIY projects with that rig. (and nothing ever failed)
That ugly DIY welder was housed in a plywood box.
OK, today I use a nice Hobart 200 amp 'real' welder but the skills learned with my DIY still pay off.