I build an electronics workbench using light-weight steel frames.
Step 1: Design Considerations / Legs / Main Structure
I was in need of a new electronics workbench and decided I wanted to use Euro Paletts for the build. However, after carrying these really heavy EUR standard paletts, I decided that the design was not feasible. I then remade the design using light-weight steel profiles used for drywall plaster board framing.
I began by measuring and cutting the 60mm profiles for the legs of the workbench. These were squared and screwed in with self tapping metal screws. I checked that the finished legs were relatively square to each other. Then it was on to the frame assembly of the workbench
For this section, I opted to use 100mm (or 4 inch) wide profiles. They were measured and cut. Throughout the structure, I created many H-beams by screwing two profiles back to back. Here's what the finished structure looks like.
Step 2: Plywood Work Surface & OSB Substrate
I then cut the 6mm (or quarter inch) birch plywood that will be the work surface. I tested the stiffness and realized that it wobbled too much. I decided to add some cross bracing where I initially wanted to have a drawer. The cross member was measured and squared and the cross braces added. This significantly improved the stiffness of the work surface.
I then attached the legs to the top structure using hex bolts and screws. I also added a horizontal cross brace that connected both legs. The plywood was glued to the top structure using a construction adhesive. However, this proved to be useless as after one day, it did not glue properly,
I then decided to put a layer of 12mm (half-inch) OSB in between the structure and the plywood work surface. This was counter-sunk and screwed to the steel frame. I checked for squareness once more and cleaned the surface. I should have used this Sikaflex adhesive from the beginning. I spread it around the edges whereas for the majority of the OSB surface, I used regular PVA wood glue.
Step 3: Finishing / Sanding / Varnishing
After I let the glue harden for a day, I sanded the plywood with 240 grit sand paper. I vacuumed and cleaned the surface thoroughly. I then applied the first layer of varnish using a solvent based polyurethane. After about 4 hours of drying, I sanded the surface once more with 240 grit.
For the second and third coats of varnish, I changed to a water based polyurethane. In between drying, I hand sanded with 400 grid and then finally 600 grid sand paper. Here you can see another horizontal brace that I connected to both legs and a few angled pieces to help with lateral stability. I used a piece of OSB left over to make a shelf using both horizontal cross braces.
This was counter-sunk and screwed to the steel profiles. And here is the workbench all built.