I picked up a used Lincoln SP-170T for a reasonable price and finally got around to messing with it last night for a while.

It's running (I think) 0.035" flux core wire for now(original spool that came with the unit!), since I don't have the stuff for hooking up gas.


I was trying to weld on some ~0.040" thick stainless pipes of varying diameters I picked up just to get a feel for it, and even at the lowest voltage it seemed like it would like to burn through the tubing. I got pretty good at just tacking it for a "pop" or two(damn this stuff can be loud!), and got it to where it wouldn't burn through as much. I couldn't keep welding on the piece for longer than about 1 second before it'd burn through if I was actually welding the piece.

It seemed like once I turned the wire speed up beyond about 3.5-4 that it would make it "lose the arc" too quickly and just pop, stop and start again, sometimes with a big chunk of wire being the whole electrode. I've read around, and is this common on thinner materials? After building up a bead and going back over it, it was much easier to control the puddle the little bit I could see of it through all the flux smoke.

I had the same experience trying to tack a few pieces of my shitbox Nissan together for the hell of it. It seemed the FC didn't want to be consistent with the arc and I had a little bit of burning through in a place or two. It seemed the thicker car metal liked the second voltage adjustment(B), and a little more wire speed, but it was still a MFer trying to not burn through but actually get penetration.

Is it also normal for the weld to really "ball up." It did this more on the car than on the stainless pipe, but there was some present on both.

I've been trimming the wire to about 1/4" out from the gun and since I have a fixed lense helmet, tending to hold it against the workpiece then pressing the trigger. Is this correct, or should I always have it away from the piece when starting?

 

the machine is a mig correct, and is sp170. tell me about whats on the front panal that has you wfs(wire feed speed) and you Volts or amperage. wfs has numbers? and voltage or amps has letter correct or wrong.

 

Correct.

I kept the voltage at A for the stainless, A or B for the car(which is thicker... maybe 18 gauge eyeballing it). Wire feed seemed to like being around the 3-3.5 range(10 is the highest).

I'm just wondering if flux core is supposed to "pop" so much and make it hard to "hold" an arc. I think thicker material would make it much more stable since I could really heat up the puddle and go slower. As it was I felt like I was rushing a bit to keep from burning through the material, or using very low volt tacks.

Also, is it bad form to let the wire rest against the workpiece when starting the arc?

 

you are running it to cold. try puting the G or F and the wfs at 7 and work your way sown on the wfs and are you pulling or pushing the gun. make sure the wire isnt old either, hope your using stainless wire also.

 

It seemed like on C, even at like 5 on the wf it would just burn right through even with a quick tack.

Couldn't really start a puddle without burning through the material, but I tried pushing and pulling and it seemed I could push the gun easier.

The wire is old - problem? It's not stainless AFAIK.

 

do you have enough current coming from your house, this had been a problem for me at a buddys house. if that doesnt work get a set of gauges and use a shielding gas and this will solve all your probs

 

the problem is that ss needs 1/2 to 1/3 the power to weld than ms. I broke in my MM135 on ss and was using 1 or 2 on the heat for .063" - ms needed settings 4 or 5; and this was with .023" wire

your wire's too thick to melt without putting all that heat into the base metal and burning through first. for .040" ss, try .030" wire and low heat

 

Sounds about right. The SS was around 0.040" thick, not sure on the alloy, but I don't think it's anything that's nice to weld since it was probably chosen for its material properties vs. weldability. Plus they do a lot of stuff in full argon chamber where I picked it up.


I'm using an adapter to run the unit to my dryer outlet, but I don't think it should be a problem since I think the unit said it only needs 20A at 240V, and the outlet is 30A.

I picked up some thicker stainless hydruaulic tubing, so I'll mess with that a little bit to see if I can weld that better.

The mild steel on the car definitely seemed like it wanted a bit more heat than the SS tubing, even though it was only thicker by a little amount.