Supposedly the aluminum wire can get pre-heated to the point where it could cause feeding issues if the actual tip diameter is too close to the actual diameter of the wire (due to expansion of the wire at the tip). Also, for example, say that the tip (which is supposed to be over-sized by about +0.002"-0.003" for the nominal wire diameter, is actually only at +0.001", and the wire just happens to be 0.001" over-sized from the factory, then it might encounter some drag/binding and bam you have a birdsnest. I do this as well as a precaution, but I supposed that it also depends on how hot the weld is. IOW if you're running at the top end of the amperage range for the wire and you have a high voltage, and your CTWD is on the lower-end of the recommended range, then perhaps. But if you're not having problems, then you're not having problems. Hard to argue with that.

 

Thanks Oscar................................
Pete

 

On the Miller 30A the tip is stated for the wire size. A .035 tip measures over .050. On the cheap spoolguns they often use the same tip as the regular mig gun. In that case a size larger would make sense. If you go too big you will have problems as well.

 

Well, you seem to have brought up something "I" and maybe a few others didn't know. I may try a .040" tip for my 030" wire.
BTW..........If I go to large what would be the first signs to look for??????
Thanks a bunch,

 

Do the tweco spoolguns fall into the cheaper gun category where oversized tips are a good idea?

 

Yes, a good (actually, necessary) thing. If you're not having problems why the question?

 

Well, I do have burn back once and a while. And listening to the size of tips on Miller guns, there tips are more than just .0005 over. So, I'm gonna try that increase and see if it stops all my burn back.

 

It's a good thing if the rated size is a "steel" tip.

i.e. you have three options for a 1mm wire: a 1mm steel tip, a 1mm "A" aluminium tip, or a 1.2mm steel tip.

If all you had is regular steel tips, then 1.2mm is the right size for 1mm aluminium... if that makes sense?

But the "best" option is a proper aluminium tip, it's the right size diameter to give good electrical characteristics without compromising on expansion. You'll get longer tip life with fewer burnbacks. I can't say I've noticed a huge difference in weld characteristics between a 1.2A and a 1.4 tip i used a while back on the same 1.2mm alu setup - you're in spray transfer so conductivity is less of an issue. But theoretically you'll get better contact = wetter bead, even if only slightly.

Not sure on Miller stuff, but Binzel always has an "A" option for all of their gun tip sizes.

 

Good clarification there. Some tips could be "aluminum tips" meaning that they are already over-sized beyond what the stamp mark says, so perhaps the 0.035" tip could actually be bored out for wire clearance + expansion tolerance clearance.

My MIG tips are over-sized explicitly, so for 3/64" wire, they are labeled as 0.052", so about +0.005" oversized. For 0.030" wire, one would simply use the 0.035" tip, and for 0.035" wire, one would use the 0.040" tip. Also you can look into CuCrZr (copper-chrome-zirconium) tips, as they handle the heat of pulse/spray arc better than standard 100% copper tips. And of course proper CTWD and arc length play a role as well.

 

There ain't no 'steel tips, nor AL tips' for Miller guns that are spooled or pushed 'n pulled. There are only bore diameters....

 

Lincoln had this figured out years ago.
Notched tips allow the operator to pop the stuck wire loose with a knife, screwdriver, random pointy tool, etc. and keep welding.
https://www.mscdirect.com/browse/tn...rm=4577060748468333&utm_content=Welders & Welding Equipment Ad Group - Supplier

https://www.airgas.com/product/Weld...ent=BPA Item - Lincoln Electric|Welding Products-MIG Gun Consumables|35-70|C:50

 

Yeah, try using Al day-in-day-out and report back with Lincoln tips...