[pro mod steve]

Practicing on 120 wall steel tube to 120 flat plate trying to learn to control hand coordination and torch angle on tube. I cut through the middle of tube,weld, and plate to see penetration with a band saw. What should I see? There were no defining lines as far as identifying tube weld and or plate it was like one solid piece on the cut line. Is this what I am after?

[jakeru]

If you polish (such as by using sandpaper starting with rough grit and ending very fine, to a mirror like finish), and then etch (using an appropriate acid for the material involved) your cut surfaces, the different zones of the metal (base metal, deposited weld bead) will become visually apparent. You can then judge the depth, position, shape, etc of your weld penetration. Any discontinuities in the metal (such as trapped flux, dirt, oxides, or porosity, etc) will also be revealed.

Here are a couple posts about the process that may prove helpful:
aluminum:
http://weldingweb.com/showpost.php?p=42 ... stcount=26

steel:
http://weldingweb.com/showpost.php?p=41 ... stcount=47