My Bandsaw Circle Jig actually started out as an idea for a disk sander jig I saw in one of my woodworking magazines. They used a sliding arm with a screw adjuster to fine tune the diameter of the circle. I thought this was neat and it slowly evolved into the arm I made for my bandsaw jig.
I already had an arm with T-slot track in it from the bandsaw project, so I figured that would get used in both jigs. You could cut on the bandsaw, then fine tune on the disk sander. The construction method I used before applies well here too. 3D print a runner to go in the miter slot, start with a base of 1/4″ MDF, then attach 3/4″ MDF on top to guide the sliding arm. I CA glued the runner in place with it all aligned, and then screwed it in from underneath.
I don’t have any features to keep the adjustment arm locked down because the disk sander’s movement should push the work piece into the table and keep it stable. Hopefully that theory continues to work out for me.
The new thing here is the adjuster. The wood magazine had something with a T-nut and bolt. It was fine, but I figured a printer could do better. The knobs were something I had designed earlier. Each holds a 1/4″-20 coupling nut. The adjustment screw is a bit of threaded rod with a coupling nut bonded to one side. The other was rounded via a drill and bench grinder. The knob will glue on to the nut and the rounded end will push up against a hard stop. Having it rounded should mean there is only point contact and will make for smoother more even adjustment.
The adjuster uses a bolt in the t-track of the adjustment arm to clamp itself down in the rough position. I added a block to the bottom of the jig and bonded a big fender washer down for the head of the adjustment screw to contact. It should be a very firm stop and won’t wear easily.
Putting it all together, and with a few coats of polyurethane to keep the MDF stable, I tested it with another sharpening wheel. My last one was a little small, so I made a new bigger thicker one. The only thing to note is that doing heavy sanding in one spot will load up the paper badly. Sliding down the table occasionally will help even out the wear.