Thanks Andrew, I think maybe I can change the gas fitting on the back of the welder to something else more common -- it isn't TIG standard and seems to only fit an oxygen fitting that torches have (did some internet research). Others have changed out the fitting or used an oxygen torch repair fitting on the hose.
My Argon regulator comes with a barb fitting for 1/4" hose, looks like, already. I suppose the actual hose type is not critical since argon is inert?
While waiting for the TIG stuff to arrive, I decided to try to do a series of arc welding tests today of 6011 6013 and 7018 1/8" and 3/32" sticks in both the Lincoln buzzbox and the Harbor Freight DC inverter in AC, DCEN, and DCEP at various amperages on 1/8" plate.
The whole exercise was very revealing and actually quite helpful to me, and will probably improve my welds in the future -- and I wrote it all down this time instead of trusting to memory -- on the wall, right above the welders!
For anybody else with the HF welder, I checked with a meter, and the stock output polarity in the stick welding switch position and with cables connected per welder case markings is DCEN.
It was hard for me earlier to keep a 1/8" 6011 stick going, no matter what the amperage. The arc would break every second or so. But that was with the stock Harbor Freight DCEN. When I switched leads to get DCEP it went easier, and a continuous weld was at least do-able, though not ideal.
The Lincoln Buzzbox (AC) produced a better weld with the same stick, which was disappointing. However, on doing some searching on the internet, I've found that many report that stick welding with the HF machine is greatly improved if the stock aluminum ground lead is replaced with a #3 copper welding lead -- I'll have to try that and see if 6011 work improves.
6013 DCEP on the HF welder worked great -- better than the Lincoln beads, it was just 6011 rod where I was having the problem. 6013 DCEP was slightly better than DCEN on the HF machine, with a bit more penetration and slightly better looking weld, though both were good.
This is the welder I have:
http://www.harborfreight.com/tig-mma-inverter-welding-machine-with-digital-readout-98233.html