Last winter I built a bunch of display cases so the Hamilton Museum could show â€¨off more of their wood type collection. I looked at the Wish List a while ago andâ€¨ saw a need for strong tables for workshop areas. I figured maybe I could make â€¨some.
â€¨I know wood working well enough to make some tables, but strong tables madeâ€¨ out of wood would probably be quite heavy. So I thought I should try making aâ€¨ table out of steel to see what design would work to be strong and light weight.
I joined a hackerspace in Chicago two years ago. It’s a place with lots of tools and â€¨benches where members can work on whatever kind of building project they like.â€¨ It’s sort of like having your own shop but quite a bit bigger. The tools includeâ€¨ every kind of power tool there is, from metal cutting bandsaws, lathes and â€¨welders to wood planers and table saws.
I got a short introduction to arc welding four months ago. Then I practiced for a â€¨month and decided I liked welding enough to get my own welder. I bought aâ€¨ good welder along with a helmet, a leather jacket and gloves. The helmetâ€¨ protects my eyes from the intense ultraviolet light generated by the welding arc.
Welding is dynamic compared to woodworking. Things are melting and flowing atâ€¨ very high temperatures. It’s fun to watch welding, even as I’m doing it. There is aâ€¨good deal of science in welding but the people who need to know that are theâ€¨ones who build welding equipment. In short, what happens is the welder makes aâ€¨short circuit on purpose to make a high temperature electric arc and that meltsâ€¨ the steel.
The practical side of welding is it melts steel instantly. To do this the welding arcâ€¨temperature is around 5,600 degrees. The electric arc is shielded from the air by â€¨two inert gases, argon and carbon dioxide, which spray out to keep the weld fromâ€¨ rusting. A weld will rust as fast as it forms if it is done in the air. A rusty weld isâ€¨ worthless, like full of holes. It can just crumble away. After doing a weld, it takesâ€¨the parts a while to cool down, so I don’t rush to pull the clamps. I need a lot ofâ€¨ clamps to hold the parts in place so I can weld them together. I got eight Vise-Gripâ€¨ clamps that have great big jaws and no teeth to hold the cross bracing in place.
I have been welding for a couple months now and I can see the welds in progressâ€¨as the steel builds up across the joint. Now I can tell if a weld is going well or if it â€¨looks bad. When a weld looks weak I just weld over it to add more steel. Someâ€¨ welds get to be downright ugly by the time they are finished, but ugly welds holdâ€¨just as good as pretty ones.
I built the table frames using three shapes of steel; flat strap, angle and square â€¨tube. The square tube is very strong and won’t flex at all no matter how muchâ€¨force is applied. I designed the frames to be as rigid as possible. Moving the legsâ€¨ in from the corners by a few inches helped increase the rigidity at lot.
Tensile strength is one of the strength tests of metals, where a piece of steel isâ€¨stretched between two points. A tensile strength rating for common steel isâ€¨ 45,000 pounds per square inch. Steel is very strong. The kind of welder I haveâ€¨will work with steel up to 1/4 inch thick. The steel I used for the table frames is â€¨1/8 inch thick and 1 inch wide.
I ended up making twelve tables 40 inches square and four tables 40 inches by 8 â€¨feet. After I got going and gathered the tools and clamps I needed, the actual â€¨production went fast. I made three of the 8 foot frames in two days. I took the â€¨frames up to the museum and cut sheets of plywood to size to make the tops. Itâ€¨ has been a real fun project and I’m sure I’ll keep welding other things for my own use.