The next step in making the shoulders hubs is to drill the holes needed to mount the hub to the leg. This required a bunch of different size drilling operations that all need to line up perfectly when they are done. To do this I started by drilling a small hole in the inner leg layer that will be right in the middle of where the hub will go. On the back of the leg piece I used a compass to mark a circle for where the holes will go and then marked the position of six holes even spaced around the circle. Next I used a nail to get the hub aligned with the leg, and then screwed both sections of the hub to the leg. With everything screwed together drilled small holes all the way through all three layers to mark the position of each bolt.
The first drilling operation was to drill shallow holes using a forstner on the back of the leg to accommodate the flange of the t-nuts.
Next I drilled the holes for the body of the t-nuts. The body of the t-nuts is a little larger then the bolt so be sure to measure them to get the right size drill.
The next holes were the large holes on the inside layer of the hub. I made these large enough to accommodate a socket wrench to tighten the bolts. Next I drilled the bolt holes in each larger whole and through both layers of the hub.
The bolts I am using to hold the flange on are not totally flush with the surface of the flange so I drilled some very shallow holes on the other side of the flange to accommodate this and allow the to sections to come together tightly.
I did some reading to see how others mounted the flange to the hub and I found that a lot of people used a metal plate on the back instead of washers. I am not sure what the advantage to this is, but I decided to still do it that way.
For the metal plate I used what most people seem to use, a cover plate for an electrical box. I started by marking the positions of the holes on the plate and drilling the holes. As always I put marks on the plate so it ended up back on the same hub and in the same position.
The plate needs to fit within a hole in the leg so I needed to trim the plate a bit. Since the plate already had rounded corners I only needed to do a little bit of trimming. I did the trimming with a hand held jigsaw with a metal cutting blade.
To hold the hubs to the leg I installed T-Nuts in the holes in the leg layer. The t-nuts have prongs that hold them into the wood, but since these will eventually be inside the leg and in-accessible, I took the extra precaution of securing them with epoxy.
There will eventually be some more assembly work on the hubs but I won’t do that until I am closer to doing the final assembly.