To really help with making your tig weld as strong and as smooth as possible, I found that changing your tig torch to a gas lense is the best thing you can do to make your welds the best they can be.

I was reading where the flow of a standard collet lense is so turbulent that it allows oxygen to enter the weld area and makes for weld contamination.

With the gas lense, the gas flow is smooth and keeps all oxygen out of the weld pool

Photos of the difference of the gas lense (left) and the regular collet lense (right)Click image for larger version. 

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The cleaner flow of the gas lense allows for the extension of the tungsten to allow for welding in tight areas.