Here’s a no-cost trick for finding the center of a dowel using a scrap of wood with a thickness that’s approximately the radius of the circle. Position the cylinder’s end against the board, then run the tip of a sharp pencil along the end and mark the edge. Rotate the cylinder approximately 90°, and make another line. Repeat two more times. The intersecting lines should create a tiny square on the end of the cylinder; from there you can judge the center by eye.
