Crafty calipers reach around the lips
I like carving wooden spoons, but determining the thickness of the bowl has always required guesswork. Traditional calipers don't do the job because they can't reach around the lip of the bowl, so I raided the scrap bin and craft-supplies box to make my own, as shown.
Make the long arms using cutoffs from the scrap pile, ripped into thin strips. Cut the arms to whatever length you need: Mine are approximately 6" long. From crafts sticks, cut four identical jaws about 11⁄4 " long and a short spacer to fit between the arms at the pivot point. Glue the spacer to one of the arms. Stack the arms and drill a 1⁄4 " hole through the center of the stack. Assemble the arms with a 1⁄4 "-20 machine screw, washer, and lock nut. Snug the nut just enough to allow the arms to pivot and hold their positions. Glue the four jaws to the ends of the arms so they touch at each end of the arms at the same time.
To use the calipers, close the jaws at one end around the workpiece. The gap distance between the jaws at the opposite end indicates the thickness.
—Keith Mealy, Oregonia, Ohio