The Taft Pierce plate is heavily ribbed and has a thick rim that doesn't lend itself to a normal welding ground clamp opening. To solve this problem I attached a c-clamp type ground clamp to a large boss on the table and then attached the spring clamp to that. You might ask why I didn't just use the c-clamp ground clamp for everything?
The lower meat of the upper arm is kind of tender in particular the older you get. I took it off and didn't think much about it. My wife spotted the purple and yellow bruise it left the next day so I had some esplaininnin to do."Honest honey its just a welding hickey" Sounds lame right? To make matters worse she is a welder also and has never had anything so ridiculous happen to her. It would have been easier to explain third degree burns over half my body or a missing limb instead of a suspicious underarm hickey.
Up to this is just the background of what I really wanted to talk about in this article which is experiments with alternate welding ground clamps. Part of the problem I perceived from my experience was that generally any particular welding machine has just one ground clamp even though it operates in a huge range of current levels and huge variety of jobs. The machine the arm pinching clamp was on is an older Miller Syncrowave 350 and can run from 1 ampere (with the low current option) all the way up to 400 amps. In welding that's a pretty wide operation range.
When you get a new welding machine most folks look at the highest amperage the machine can produce and size the ground clamp to accommodate that highest current even when they know the machine will see that only a few times in its life for the average machine. I Asked myself the dumb question why don't we just have some quick change ground that we match to the job? What could I try on the cheap? If I went to a quick change setup I would need a quick disconnect to mount to the machine and a handful of the opposite side for the different clamps I envisioned. That would have taken too long and cost a couple hundred bucks just for an experiment. So I started poking around the bins in the old electrical cabinet. On the TIG machine I have at home the original owner really took the top end current ability to heart when they sized the ground. Its ground cable is something like 4/0 cable. It weighs a ton and to add insult they skimped on the length. Probably because the huge cable is so expensive per foot. On the same note a huge ground makes no sense when on the other end a lightweight 200 amp TIG torch is mounted.
Try it. I think you will like it as much as I do and its an easy afternoon project.