Make Something Big
For this week's assignment, "Make Something Big", I decided to make something long. Specifically, I made a beam from a 4' x 8' sheet of OSB using a modified version of a type of Japanese scarf joint known as kanawa-tsugi. The kanawa-tsugi
relies on a sandwich of two distinct profiles that together create a geometry that interlocks with itself. I find that very satisfying. There is no "positive" or "negative" side of the joint because each side is identical. See a model of this
joint below created by The Joinery.
The first step was to parametrically sketch the joint geometry in Fusion 360. Once I had this set, I moved the design over to Rhino. I'm still getting the hang of Fusion and I find that for quickly copying and moving around geometries, Rhino
is much more straightforward. In Rhino I also added holes along the length of the beam sections just to serve as registration keys for gluing up the kanawa-tsugi sandwich. In addition to the pieces for the beam sections I also milled out a
strip at the correct width to be used as keys for the registration holes as well as wedges that I would later use to drive the joints together.
Once the geometry was set it was time to lay it out on the stock and import it into MasterCAM. I used three toolpaths: one for drilling out the internal corners with a 1/4" drill bit; one for clearing out pockets with a 1/4" downcutter; and
one for cutting out the parts with a 3/8" compression bit. Overall the milling went well though I did have some issues with parts that weren't all that small coming loose. I think a more agressive onion skin or tabs should have been