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Retrofitting a MillerMatic 35 Mig Gun

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  • #46
    Originally posted by mein-bob View Post
    I have a couple of questions, i see the lincoln adapter and not quite sure how you attach it to the plastic plate and would you still use a m25 gun like the black face model? i do see tweco makes a conversion kit which will work with the tweco guns. i hear the tweco guns are reliable but never used one. and lastly the black face has 10 capacitors where the white face has 6. can i just swap out the capacitor pack ? been using the black face for 30+ years but it has been worked hard. did not realize there was a difference until i just picked up a white face mm35 in way better shape then mine. of course gun is no good.
    thanks for any input.

    I know this is an older thread, but someone just asked me a question on the topic so I thought I'd reply and add what little I can.

    I've done several conversions on MM35 and 35S using this basic model. I use a hole saw to cut a hole for the gun adapter, then epoxy the Lincoln adapter into place in the acrylic board. I actually bought a 1/2" thick cutting board at Menards and then cut a section out of it to fit the inside of the panel.

    I place the acrylic on the inside of the panel and secure it with a couple of clamps. Then I drill holes at four corners, and secure with bolts/nuts. At that point I use a piece of liner material coming out of the wire feed to mark where I want the center of the adapter on the inside of the acrylic plate. I then remove the plate and drill a pilot hole, reinstall the plate to the welder and then use a hole saw to cut a larger hole in the face of the welder, without cutting much of the acrylic. At that point I remove the plate and use a hole saw in a drill press to cut the hole for the Lincoln adapter. I like to do that on the drill press to keep the hole square to the board. Usually that's also when I cut a larger hole for the power lead and gun trigger receptacle as well.

    I set the Lincoln adapter on the workbench vertically and use a couple of 2" blocks of steel on either side of the adapter to support the acrylic plate, get things straight and then wrap a bead of epoxy around where the adapter comes through the acrylic. The adapter probably protrudes a bit less than 1/4". After the epoxy sets, I flip it over and wrap a bead of epoxy around the inside and let the whole thing sit for a couple of hours (fast set epoxy is fine and strong enough).

    You'll need a hole through the face big enough for the torch trigger switch receptacle and a couple of holes to screw it in place, and it works better if the hole in the acrylic is much larger so you can get to the inside where the nuts will go. You'll also need a hole through the face for the power lead that connects to the Lincoln adapter. I like having a larger hole through the acrylic there as well, and add a grommet to protect the lead from the metal it runs through.

    If you don't have a later model with an internal valve/solenoid, the easiest thing to do is find a 24V DC solenoid/valve on Amazon or eBay...they're pretty inexpensive. I made a bracket out of angle iron, drilled a couple of holes and mounted the solenoid to it, then found an unused hole in the body of the welder and ran the wires to the circuit for the torch trigger (it's 24V). I'll try to find pictures and add them later, but it really doesn't matter where the solenoid goes. There is a hole where the gas line came up from the bottom of the machine and attached to the gun, so that's an easy route for the new gas line.

    You'll have to make a couple of electrical leads to go from the back of the torch trigger adapter to the trigger circuit receptacle, but they use normal spade connectors and the trigger adapter kits come with the correct plug connectors you need for the receptacle side, so it's not complicated.

    The one tricky thing I've found is that the wire feed is designed for a gun liner that's wrapped in a heavy plastic/rubber layer. If you try to put just a piece of liner in that spot (to guide the wire to the gun end) it won't line up at all and the wire won't feed properly. If you have the old gun you can cut a section of the liner and use some of that as a guide. I've also found a piece of brass tubing that fit in the wire feed properly and also was the right ID for the liner. Drill a hole in the side of that so that the set screw pushes on the liner and you're set.

    That's all I can think of now, but I'll add more with pictures if I can find them.


    • #47
      This is the first machine I converted, and I did it slightly differently the second time, but close enough to illustrate the point.
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