The slot is beveled so that when the dies are used in a machine holder the adjusting screw can be removed and adjustment made by the adjusting screws in the holder.7/16"-16 UNS X 1-1/2" OD HSS Round Adjustable Die Adjustments are made by a fine pitch screw which forces the sides of the die apart, or allows them to spring together. Round dies are chamfered on both faces, one side has a 2 to 3 thread chamfer for threading and the other side has a 1 to 1-1/2 thread chamfer for threading close to a shoulder..