Abstract: A cutter with replaceable cutting elements is adapted to be mounted upon the rotary head of an earth boring machine or upon the body of an earth boring bit. The cutter is used in conjunction with an earth boring machine that functions to form circular kerfs in the formation being bored to fracture rock between a proximate pair of kerfs in a manner to cause fragments of the formation to be separated from the formation being bored. At least one annular cutting ring is mounted on the periphery of the cutter body for contacting the formations and forming a kerf therein. The cutting ring is in the form of a pair of substantially semicircular disk elements that fit upon the periphery of the cutter body. A corresponding pair of semicircular locking elements with taper surfaces are positioned in overlapping relation to the disk elements. The locking elements are securely bolted to the cutter body and insure that the disk elements remain in the proper position for the earth boring operation.