Multiple Pass versus Single Pass? Part 1

Yesterday, I received a call from a customer really struggling with welding problems.  As human nature is, he wanted to know what was wrong with the product, rather than consider any possible issues he had in technique that incurred the problem. I began to ask a few basic and routine questions about settings and practice.

I came to find out, as I had many times before that he was trying to make a single pass weld on a quarter inch piece of plate metal in a single pass with TIG.  He had the welding unit cranked up to maximum and was struggling with penetration, porosity, and overall contamination.  He first told me he thought he bought too small of a welding unit. But it wasn’t the machine or a problem with its size. The problem was he was tackling it in the wrong way.

First, when welding, consider the overall thickness of the piece of metal you want to weld.  Is it over 1/8”?  If it is, you will definitely need to bevel the joint to get the best results and achieve full penetration. You cannot weld any metal fully over 1/8” in a single pass in any practical manner with most average equipment.

You see many advertisements selling welders for their maximum single pass weld capability. But there’s no explanation given as how it is accomplished. It’s not an item of trickery, but there is a lot of theory that goes into this recommendation that is based on a lot of theory, and not necessarily practicality.