Snap On MW120 MIG Welder

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RustyRatRod

RustyRatRod

I was born on a Monday. Not last Monday.
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A good friend gave me a Snap On MW120 mig welder. All it needs is a new liner and everything else works. He had a parts list for it but that's all. I guess I'm stupid because I cannot find a lot of info on it online. Some sources say it was made by Century and some say Snap On actually made it. I ASSUME the 120 means 120amps, although I've welded with it in the past myself and this thing breezed through 1/4 plate with a single pass very easily, so I wonder. Maybe it just has a really good transformer. It's 120V, btw. has a nice Tweko torch, like my Craftsman. I thought I would outfit one with small wire for thin metal and the other with either .035 or .045 for thicker stuff. Any of yall familiar with this welder? Thank you drive through.
 
If it has a tweco mig gun then go to tweco for the liner. A snap on dealer can get you the parts but expect big $ for a small cost.
If you bring the gun assembly to a welding supply dealer they should be able to match up the liner.
Being it is a 120- what is the plug on the wall side? 120vac or 220vac?
That and the wire diameter will dictate the steel able to be welded. Also duty cycle will dictate how long you can weld for.

SN: I own my own welding shop for 27 years now but a welder for almost 40.
PM me if you have any questions.
Syleng1
 
Snap On used many different manufacturers over the years to make welders for them. Basically whoever was cheaper. I do think that this was one that Snap On had made themselves. Don't let the 120 fool you though as many manufacturers started playing games with the number designation over the years. I do believe it is an 80 amp output with a 30% duty cycle but that is going off of memory as it has been a couple years since I have had one in to repair. As said for a gun liner a standard tweeco liner will work and a welding supply store would be your best bet
 
Yes it has the Tweco gun and liner. I put a new liner in it today with the same results. The problem is it wads the wire up going into the beginning of the liner. It takes a while to do it though. The wire has to be damn near to the gun before it does it. Just for kicks, I tried spraying some penetrating oil in the liner.....I know you're not supposed to, just for diagnosis. And it fed great.....until it dried out. Also, I can cut the wire before it enters the liner and it feeds all day long. It wads the wire up no matter how tight I tighten it. I can pull the wire through the liner manually, but it does take pliers and does have some resistance. The old liner I removed, the wire was completely stuck.

Also it does "try" to weld but it never strikes an arc. It feeds the wire (when it will feed) the wire hits the work, turns orange and falls off. Seems to work "best" with the wire speed almost all the way down and the heat way up.

It's a 120V, btw with a standard grounded 120v plug. Any help is appreciated.
 
RustyRatRod said:
A good friend gave me a Snap On MW120 mig welder. All it needs is a new liner and everything else works. He had a parts list for it but that's all. I guess I'm stupid because I cannot find a lot of info on it online. Some sources say it was made by Century and some say Snap On actually made it. I ASSUME the 120 means 120amps, although I've welded with it in the past myself and this thing breezed through 1/4 plate with a single pass very easily, so I wonder. Maybe it just has a really good transformer. It's 120V, btw. has a nice Tweko torch, like my Craftsman. I thought I would outfit one with small wire for thin metal and the other with either .035 or .045 for thicker stuff. Any of yall familiar with this welder? Thank you drive through.
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I sold Mac for 3 decades but that is a good one. Probably 1/4" capacity. Use .023 and let her buck. A welding supply company should be able to help you with the liner.
 
RustyRatRod said:
Yes it has the Tweco gun and liner. I put a new liner in it today with the same results. The problem is it wads the wire up going into the beginning of the liner. It takes a while to do it though. The wire has to be damn near to the gun before it does it. Just for kicks, I tried spraying some penetrating oil in the liner.....I know you're not supposed to, just for diagnosis. And it fed great.....until it dried out. Also, I can cut the wire before it enters the liner and it feeds all day long. It wads the wire up no matter how tight I tighten it. I can pull the wire through the liner manually, but it does take pliers and does have some resistance. The old liner I removed, the wire was completely stuck.

Also it does "try" to weld but it never strikes an arc. It feeds the wire (when it will feed) the wire hits the work, turns orange and falls off. Seems to work "best" with the wire speed almost all the way down and the heat way up.

It's a 120V, btw with a standard grounded 120v plug. Any help is appreciated.
Click to expand...
What size is the wire and tip. Is the wire old?
 
Bodyperson said:
What size is the wire and tip. Is the wire old?
Click to expand...
.035 for both. It probably is old, because it's almost at the end of the spool. But would that cause it to wad all up and not feed properly?
 
Try feeding it of the opposite side of the spool, sometimes that makes a difference
 
diymirage said:
Try feeding it of the opposite side of the spool, sometimes that makes a difference
Click to expand...
I tried it. That actually makes it worse, because it feeds in at a greater angle. Whatever the problem is, it's ahead of the feed rollers.
 
RustyRatRod said:
.035 for both. It probably is old, because it's almost at the end of the spool. But would that cause it to wad all up and not feed properly?
Click to expand...
Think about it this way. A 120 volt/amp welder doesn't have enough power to melt .035. They use that in the 250 amp 220 volt welders.
 
RustyRatRod said:
.035 for both. It probably is old, because it's almost at the end of the spool. But would that cause it to wad all up and not feed properly?
Click to expand...
Maybe. Just spitballing. So many variables. I’m assuming flux core. maybe some corrosion on the wire or swelling of the flux. Cranking on the feed tension is never a solution. When everything is running smoothly, you should be able to stop the wire with your hand at the tip and the rollers should just slip on the wire and feed again when you remove the obstruction (your hand).
 
toolmanmike said:
Think about it this way. A 120 volt/amp welder doesn't have enough power to melt .035. They use that in the 250 amp 220 volt welders.
Click to expand...
Hence why he has the wire turned down and the heat all of the way up.
 
toolmanmike said:
Think about it this way. A 120 volt/amp welder doesn't have enough power to melt .035. They use that in the 250 amp 220 volt welders.
Click to expand...
The heck it doesn't. My Craftsman 120v MIG melts .045 all day long and welds 1/4" plate in a single pass. This Snap On welder is simply not working right.
 
Bodyperson said:
Hence why he has the wire turned down and the heat all of the way up.
Click to expand...
The welder is malfunctioning. I've been welding since I was about 13. I know when one's not working right.
 
Bodyperson said:
Maybe. Just spitballing. So many variables. I’m assuming flux core. maybe some corrosion on the wire or swelling of the flux. Cranking on the feed tension is never a solution. When everything is running smoothly, you should be able to stop the wire with your hand at the tip and the rollers should just slip on the wire and feed again when you remove the obstruction (your hand).
Click to expand...
No, it's MIG. 75/25 Argon. Right. That tells me the gun is most likely the issue. "Whatever it is" is in front of the feed rollers.....and that's about all there is. lol It feeds fantastic bypassing the gun.
 
So it’s still obviously the liner. You tested it right? Independent from the machine? You feel drag in there when pulling the wire back and forth? Sometimes one of my machines will start piling wire like I have a bad ground but it is the contact on the heat switch. I have to jiggle it a little to get my amperage back but I don’t think that is your issue.
 
How tight is the spool ?
(Amd I'm not trying to be obstinate, but I've seen this happen)

If the spool is too loose it can "run away" ,in essence pushing against the feed rollers

Hey, the feed rollers do match the wire, don't they ?
 
Bodyperson said:
So it’s still obviously the liner. You tested it right? Independent from the machine? You feel drag in there when pulling the wire back and forth? Sometimes one of my machines will start piling wire like I have a bad ground but it is the contact on the heat switch. I have to jiggle it a little to get my amperage back but I don’t think that is your issue.
Click to expand...
It takes a good bit of effort with pliers to pull the wire through the liner. I don't think I could do it by hand. ....and yes, without the liner involved, it feeds like a sumbitch.
 
diymirage said:
How tight is the spool ?
(Amd I'm not trying to be obstinate, but I've seen this happen)

If the spool is too loose it can "run away" ,in essence pushing against the feed rollers

Hey, the feed rollers do match the wire, don't they ?
Click to expand...
I've tried it with the spool tight, in between and with the bolt almost falling out. Yes, it had a dual size roller. .035-.045 on one side and .020-026 on the other. It pushes the wire better on the .020-.026 side though, even though that doesn't match the wire.
 
RustyRatRod said:
It takes a good bit of effort with pliers to pull the wire through the liner. I don't think I could do it by hand.
Click to expand...
.23 wire might be an easy fix. You want it for lighter gauge any way though you F‘d it up withe the penetrating oil. Can’t believe you did that.
 
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