This is a jig for making and gluing up pen blanks from wood discs. It is pictured loaded with discs clamped as for gluing, with a sampling of discs around the base. Sometimes I actually make a thing on the Glowforge. Mostly though I make the thing that makes other things. This is one such tool.
The base has 1/4x20 threaded inserts into which are seated two threaded rods. The center rod is aluminum that has been polished shiny and waxed. The top has matching through-holes for the 3 rods. Acrylic plates line top and bottom to ensure the discs don’t get cemented to the wooden base or top.
Since the wood base and top are too thick to cut, the “made on a Glowforge” bit is that scrap wood was used to make drilling patterns for the top and bottom, as well as the acrylic plates.
From a design perspective, it is convenient if the top and bottom do not need to be lined up in a consistent left-to-right direction. To achieve that the spacing of the rods from each other and their centering in the wood blocks along two axes needs to be precise. That takes a fair bit of skill to achieve with normal woodworking tools, but is drop-dead simple with Inkscape and Glowforge.
The design requires three templates:
- The drill template for the bottom has a hole to fit the aluminum rod but the other two holes are sized to position a drill bit large enough for the threaded inserts. Length and width match the bottom block of wood.
- The template for the bottom layer of acrylic is similar but the holes are sized for the aluminum rod (6.5mm) and the two 1/4x20 rods, which are much smaller in diameter than the holes for the threaded inserts.
- The top template has the same hole pattern as the previous one, but length and width match the top piece of wood. Two additional holes are cut to allow small screws that hold the acrylic loosely to the wood.
Since the holes are precisely spaced, grouped, and centered, the top part of the clamp slips on easily regardless of left/right orientation, as per the design spec.
The discs shown are also cut on the Glowforge. The center holes are intentionally snug on the aluminum rod to help hold the disc alignment during assembly. Some projects call for all the grain to be aligned, while others might call for it to be staggered or crossed from layer to layer. In either case you want to discs to be somewhat resistant to rotation from a careless touch. The glue has a tendency to reduce friction and the snug hole size attempts to compensate for that.
Here it is in action and demonstrating the need for the acrylic bottom plate. Once the clamp is fastened on and screwed tight there will be considerably more glue squeeze-out. Since PVA glue bonds are often stronger than the wood itself, and since the clamp is made of oak, the whole thing would be a 1-time-use sculpture jig without the acrylic.
The first project off the jig is presented over at the Coral Snake Pen topic.