Misc:
When I started welding aluminum with my MIG it took a little while to get a feel for it, but within my work envelope I feel like I can get satisfactory results. The one thing I can't seem to eliminate is melt back into the tip of my gun. For a small to mid size project I would go through a couple tips. For a large project tip replacement would get downright expensive. I have a Miller 212 w/ a 3035 spoolgun. I always figured it was just me so I started buying tips from USA Weld (HTP America) in bulk. Someday I figured I would finally master that problem, but in the mean time... I found their tips to perform exactly the same as the Miller replacement tips at a fraction of the price.
A week or so ago I found my spool gun laying on the floor with a bent nozzle. The center tube was bent, and the ceramic insulator was broken. :( I did a little research on parts, replacements etc, and discovered I am not the only one having melt back issues with this gun. One fellow claims that the problem is that the miller tips are too thin at the tip. I don't recall what all the explanation is, but basically he shortened the inner tube and drilled and tapped it to take the regular mig tips which are thicker to the end. He claims he no longer gets the continuous melt backs that ruin so many tips. Interesting. I may try that.
In the mean time I ordered a replacement nozzle assembly for my spool gun from USA Weld. They claim it is identical to the Miller and even made in the same factory. It may be made in the same factory, but it is not identical. I took it all apart and looked it over. For the most part it is the same, but I found two difference from mine. The brass nut that attaches the nozzle to the gun has an easy grip plastic shell over the nut on the USA Weld version, and the hose barb has two ridges instead of one. Both in my opinion are improvements over the Miller Nozzle I have.
When I chase one down I do plan to order a replacement center tube for my Miller Nozzle so I can fix it just so I can do the cut and tap mod to it and see if it really eliminates or substantially reduces melt backs.