Bar Clamps Build Process

3/5/2021

The first thing I did in the build was some investigation into welding the threaded bar to the box section. This is an important part of the design and it's important that the welds are relatively tidy so that the screw jaw can slide freely and the half-nut in the sliding jaw doesn't interfere with the weld beads.

In the original video, Neil Paskin used his gasless MIG welder to attach the threaded rod to the box section. I don't have a MIG welder, so I needed to explore other options. The threaded rod I have came with zinc plating; to TIG weld this I would need to remove that plating, but that would expose the threaded rod to the possibility of rust and it can't be painted as the thread would no longer be usable.

My first attempt to overcome this was to get the arc welder out. My arc welding skills are... well... limited, as you can see in this photo (which was my fourth attempt). I could have carried on practising and I'm sure I would have got there. However, I noticed that the zinc plating near the weld beads had turned a matt grey. I suspected that this was a sign that the zinc plating had gone, so I sprayed the sample with some water to see what happened.

As I suspected, the plating is no longer doing its job, so this doesn't seem like a good option (even if I could master the art of arc welding).

Given that the zinc wasn't surviving the arc welding and that TIG welding is a much more pleasant process (fume- & splatter-free and also a lot more controlled), I went back to TIG - the test piece is shown above. It will still be susceptible to corrosion, so I will have to apply some ACF50 or Metalguard or similar. My workshop has a dehumidifier running all the time (controlled by a humidistat) and there's lots of unprotected steel. So far I haven't had a problem with rust, so I'm hoping that these new bar clamps will survive. Apart from the box section and threaded rod, most parts of the clamps will be painted or can easily be oiled without risking getting oil onto the wood being clamped, so it shouldn't be too bad and I can always replace or de-rust the box section bars if they do corrode (as these pieces are quick and easy to make). I could have used stainless steel for the box section and the threaded rod, but this would have been a heck of a lot more expensive.

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