TIG'ing 6061 Aluminum??

[CGCINC]

I have a local machine shop that has me fix mistakes in their machining.... fill mis-drilled holes...etc.
It is usually 6061 Aluminum and I have a hard time welding it.
It just never "flows" like the Aluminum I order from my local supplier.... not sure of the grade but I'm guessing T3xx

I'm just wondering if you guys set your machine different for different grades of Aluminum?

[sportbike]

6061 is pretty standard. Filler 4043 will flow a little better, but can result in lower strength for thicker material (3/8" and greater).
What filler are you using?
Autogeneous welding of 6061 is not recommended as it will be crack sensitive without additional alloying with the filler metal.

[CGCINC]

I'm using 4043 filler.

I used to do really nice welds on Aluminum with my 250ex but the last three jobs I've done in Alum. has not worked so great.
Maybe the machine is at fault?!?!? I used to love this welder for Aluminum but it seems either I've lost the majic touch or something is not right...

[Mike J]

Did you try some test coupons with metals you know, and you confirmed no contaminants in your brushes or cleaners? You might have to experiment to isolate where the issue lies.