Four Square Chair

Step 3 Machining the Aluminum

This step sucks. It's really tedious and time-consuming, but essential for a fresh product. I estimate I spent the better part of 30 hours just on these joints, and I still could have gone to finer and finer grits to get a mirror polish. That said, I could have cast them thinner, and, in retrospect, saved myself a lot of time.

The first picture shows the joints fresh from the mold, still coated with some sand. I machined the joints down on a band saw first, to remove the bulk of the material. Then I built a jig to hold them steady and used a 1/4 sheet orbital sander to grind them down with really coarse paper. I think I used floor refinishing sandpaper at sixty grit first, then worked up to 150 or so to smooth them out. The bench sander comes in handy here as well, but keep some water handy because the aluminum gets real hot, real quick. Always wear gloves and a dust mask when machining aluminum, or else those little bits of metal are ending up in your lungs.

After the dimensions were satisfactory, I drilled 3/4" and 1/2" holes on a drill press. Aluminum is pretty soft, so this part went mercifully quick.

The second picture shows all the raw materials laid out. After cutting my sixteen pieces of wood to width and length, I paired them up with masking tape and drilled holes in them on the drill press. I kept each pair together, so I knew whatever small inaccuracies visited upon each piece would at least have a symmetrical partner. This is also a good time to slap a couple coats of polyurethane on the wood, because certain sides of it will be pretty inaccessible as assembly gets going.