I needed two new workbenches. My old one was constructed of 4×4 timber and free-standing. Trying to cut something in a vise with a reciprocating saw or even a hacksaw would set the whole bench to vibrating.I wanted a bench that was strong enough and heavy enough to stand alone, but also readily able to be bolted to the floor and the wall. It also had to be constructed in such a way as to allow the counter top to be replaced every few years if necessary. It had to be a comfortable height for me to work either standing, or sitting on a stool. Materials had to be easy to source and the best compromise between strength, weight, cost, durability and appealing cosmetics.
I did all of the welding by myself, however this really is a two person job. Even with multiple clamps, I had the table topple over several times as I set it up for welding. Appropriate clothing and safety equipment is a must. Metal fabrication in cut-off shorts and sandles will eventually lead to problems (such as when my pants caught fire). I strongly recommend an assistant as the combined weight of all the pieces can be difficult an possibly dangerous for a single person. Here my assistant cuts angle-iron. Yes, the picture is posed. She should be wearing a full face-shield, long sleeves, gloves, etc.
The angle iron at my local steel supply center came in 20′ sections. Based on space available, and the availability of pre-cut counter tops, I selected 10′ as my length. I had the front and back 10′ sections and the legs saw-cut at the steel yard. The nominal cutting fee was well worth the money, as cutting 3″ angle iron is difficult, even with a good chop-saw. You may prefer 12′ or 8′. My old bench was 8′ and I found that to be a bit constricting when I had more than one project going on at the same time. Take into consideration not only the footprint of the bench, but the necessary work area around it. As a right-handed person, I prefer the vise to be mounted on the left side. The purpose of the close spacing of the legs on either side is to provide good support for the 6″ Wilton vises I use. Be sure to read through my reasoning for the sizes I list. You may want to make slightly different lengths.