|Project by Gianni||posted 10-12-2014 10:44 PM||1334 views||3 times favorited||1 comment|
The batmobile bed project required repeatable large circles for the wheels and rims, so I decided it was time to build a “proper” circle jig. This has been considered often enough that I had already surfed for plans and picked out one that had the features I liked.
This one runs in the miter track (I bought a plastic cutting board from wal-mart that I hack up whenever I need a track piece) and stops on the front of the saw table. It allows me to cut the wood oversize and slide the wood and jig onto the saw together; this eliminates any guesswork about finding the edge. The adjustment piece was ripped at 15 degrees and slides in and out between two pieces glued to the base.
It locks in place with a thumbscrew from underneath. The original plan hallowed out a spot for a penny beneath the track to keep the thumbscrew from digging into the slider, but as a hobbyist I’m not too concerned about wearing it out. I did consider adding a T-nut between the base and the block that supports the screw, but just threaded into the ply tightly amd that works quite well. Again, if I was using it daily, a little more durability could easily be added.
The plan had additional thumbscrews in the front stops to dial in the depth of the blade with respect to the pin. Because of this, I set the pin a little deep thinking I’d add them if needed. With the pin just behind the teeth, there was no need. I ran a quick test cutting a 4” circle, then slid out to cut the wheels at 22 and the rims at 16. Slick as can be.
Quick edit, I should’ve mentioned it will go out to about 4 1/2 feet or so, and it’s wide enough to clamp the left side to the table if the workpiece is heavy and on a long lever. The strength of the dovetail is probably the limiter there.