Is the filler rod ER 70S2, if it is you have the correct filler. If it is RG45 you have an oxy-acetylene rod and should not be used for GTAW. You may want to drop back to 1/16" diameter filler rod for the 1/8" thickness.
Undercutting is usually the result or too much heat, or wrong angle of the tungsten. I agree that you probably have oxy/fuel filler wire. Allthough it is unlikely, check any way to make sure you have the proper gas and not a mix gas like 75/25. You should be using pure argon.
Mike
yes I just checked and the filler has r45 stamped on the end of it. I told the guy I needed 3/32 tig rod for mild steel I guess he sold me the wrong stuff. thanks for the help can you use filler for stainless on mild steel cuz a buddy gave me some 1/16 stainless rod but I have not tried it.
No problem using stainless filler on carbon steel.
When training our welders, we usually use ER308L or ER309L on carbon steel material. The technique is the same and the cost of material is cheaper.
Good-luck!
Thanks for the help I love this site everyone is very helpfull!
yes it was all about the filler rod I got some new rod and it made all the difference