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Retrofitting a MillerMatic 35 Mig Gun

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  • G-ManBart
    replied
    This is the first machine I converted, and I did it slightly differently the second time, but close enough to illustrate the point.
    Attached Files

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  • G-ManBart
    replied
    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.

    bob
    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.

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  • mein-bob
    replied
    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.

    bob

    Leave a comment:


  • cgb
    replied
    Greetings... As probably one of the last people on this side of the planet that owns a 1975 MM35S and still has the original equipment Miller gun installed, I am very interested in garybdavis's earlier posts this year. I have begun my upgrade project by installing a solenoid for the shielding gas (the mechanism in the original gun never worked correctly), and am very pleased to finally step into the 20th century, and not have the hassle of turning the gas on and off all the time.
    However, it is time to take the next steps; I have purchased one of the aforementioned Lincoln K3347-1 adapters, and procured a copy of the original Miller upgrade instructions to guide me. What has evaded my search are the details on the 4 pin (it is 4 pin, yes?) trigger connector. The panel mount connector appears to be an Amphenol, are there any part numbers available for that? I assume the panel connectors are sockets, and the gun side has the pins?
    I have a number of questions that would greatly assist my progress, but I don't want to post all of them online. If someone skilled in this transition would be kind enough to contact me, any information would be greatly appreciated. Any suggestions for a reasonable priced replacement for this gun (am on a tight budget with the holidays) would also be greatly appreciated. Thanks!

    Happy Holidays to all.
    Bob

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  • aametalmaster
    replied
    Great. Glad it all worked out...Bob

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  • garybdavis
    replied
    The upgrade is finished and everything worked out very well. I ordered the K3347-1 part from Lincoln which is a modern Miller Power Pin receptacle. My machine already had the solenoid kit put in so that part was there. I also ordered the 4 pin electrical receptacle that the gun trigger plugs into.

    I had to source two more parts: an acrylic plate and plastic shoulder washers to isolate the mounting plate from the welder frame. Both came from ebay. I cut the mounting plate on my CNC plasma table.

    While I was in there, I cleaned the drive wheels and replaced the missing Woodruff keys. I painted the outer case and ordered some new Miller logos for it.

    The gun is a cheap aftermarket but runs Miller M25 consumables. My other guns are Bernard Q300/Q400. The MM35 is welding is going to a family member who is just getting into welding so he can update the gun when this one wears out.

    The machine still welds like a dream and the drive is good and strong – even when the lead is coiled a bit tight. I’m kind of sad to see it go. I’ve build just about anything and everything with it and it’s been my main welder for the past 25 years or so. But I know it’s going to a good home.

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  • garybdavis
    replied
    Well, I took the plunge and ordered the part along with the connection plug for the gas solenoid/drive motor. Will post the results when I'm done.

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  • aametalmaster
    replied
    It looks right to me...Bob

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  • garybdavis
    replied
    I know this is a really old post, but 10 years later, I'm needing to replace my gun on my Millermatic 35. It currently has a Bernard connector on it but I want to configure it to accept a standard Miller MIG gun. What I really need is an aftermarket coupler that I can can fit onto onto the MM35 and I think I've found one. Lincoln makes a K3347-1 which is described as "Gun Adapter Kit, Miller". It looks like its the right size and has the lug and nipple to connect the lead and hose to. I spoke with Lincoln but couldn't get verification. Can anyone verify or offer an alternative?
    Attached Files

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  • KULTULZ
    replied
    And thanks to all you gentlemen again...

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  • Desertrider33
    replied
    I forgot to say...

    Thanks, Kevin, for confirming that info about the gas valve for us, very helpful.

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  • Desertrider33
    replied
    Sounds like a plan to me. You may be able to put some fresh o-rings in the valve in the torch too, if it has them.

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  • KULTULZ
    replied
    Again, Thanx Gentlemen.

    I think what will have to happen is to plumb in the newer valve in the machine and keep the mechanical valve in the gun as it has a special outlet design.

    Does this sound OK?

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  • Kevin
    replied
    You are correct, when the gun was changed to a GA-20C in 1980 an electronic gas valve was added to the machine to control the gas supply. The drive housing was also changed at that time to accomodate the larger power pin on the GA-20C.

    Kevin

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  • Desertrider33
    replied
    Yes, argon is through the roof right now, for some reason. At work, a 300 cu.ft. tank of it lasts only ~2.5 days per machine (we do production welding). We go through a 230 liter liquid argon tank every 3 weeks....

    One thought- have you called Miller parts dept to find out if the gas valve in that torch is still available as a replacement part?

    Barring that, If the Millermatic 35 after 1980 has a gas valve/soleniod in the cabinet, as I now suspect, I would first investigate to see if these parts can still be purchased, as that would be the easiest way to get a gas valve into your friend's machine. If not, then I would look to another, later model Millermatic that does have a gas valve in it (like a MM200, 250, etc) and see about availability of those parts and adapting that to your freind's machine.

    You may want to remove and/or by-pass the mechanical gas valve in your torch if using a gas valve in the machine, if the valve in your torch is leaking and can't be fixed.

    In one parts schematic I was looking at for, I think it was Millermatic 251, 252 or 350, the gas valve/solenoid (all one unit I think, from the picture) was, as I remember it, 12 volts and looked to be a good candidate for retrofit into something else. I wasn't looking for info on gas valve at that time, just got to thinking about that as I saw it on the schematic and parts list. The gas valve/soleniod is all one unit in my Cobramatic feeder too, as I remember it. It wouldn't surprise me if most of them now days are one unit.

    We have electric solenoid operated air valves on most of the machines at work that I work on often. On these, the soleniod is a seperate unit attatched to the top of the valve. I suspect a search of the Grainger or McMaster-Carr or Western Enterprises catalogs might come up with an inert-gas valve and a solenoid that could work for your application if one cannot be easily acquired from another welding machine.

    The parts schematics and parts lists for most Miller welding machines can be found on the last few pages of their owner's manuals, which are available for free download if you go to the 'Resources', then 'Owners Maunals' section, at the top of this website and search for the machine of your choice. You need to have Adobe Acrobat reader program on your computer to view the manuals in their .pdf file format. This has been a great resource to me since some of my machines are old and were purchased used so I didn't get a manual with them.

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