This little device if carefully made will enable one to accurately determine the centers of round bars, disks, and in fact any object of a circular form. A piece of 3/16-inch square brass rod about 8 inches long is bent to form approximately a right angle, both legs being of equal length. A strip of brass,A, about 3/8 inch wide and 1/16 inch thick is soldered to the ends of the legs. Equidistant between points X Y make a mark b. Another brass strip B of same size as A is soldered in place as shown, being careful to have edge C exactly on the line b and over the angle D. Fig. 119 shows method of using the device. Simply place it on the end of the bar or shaft; make a mark with a scratch awl; give a quarter turn, and make another mark. The intersection of the lines will give the exact center.

Fig. 119 - Device for finding centers of round work.