A set of nice trammel points or an oversized compass can be quite expensive for the hobbyist woodworker that I am. So, I made a big compass from materials I had on hand: a length of aluminum T-track, two 11⁄2″-long T-bolts and knobs, two 1 x 2″ blocks of scrap, a pencil and a screw. As you can see, the bolts and knobs hold the blocks at any position along the T-track, so my compass is completely adjustable. I drove the screw through one block to serve as the pivot point, and I drilled a hole through the other block to hold the pencil. A band sawn slit up to the pencil hole enables the bolt and knob to grip the pencil securely. Here’s a sturdy compass that will only be limited by the length of your T-track.
– Serge Duclos