A cutter assembly is presented for mounting to one or more hammers of a rotor assembly of a grinding machine. The cutter assembly includes a base, a tip mount, at least one cutting edge and a wedge releasably secured to the tip mount, and a fastener securing the base and the tip mount to the hammer. The base includes a truncated pyramid key and the tip mount includes a corresponding truncated pyramid keyway. A wedge edge angle is defined between a wedge top face and side face. A cutting edge angle is defined between a cutting edge knife face and top face. The cutting edge angle can be larger than the wedge edge angle. The cutting edge angle can be in the range of about 30° to about 40° and a wedge edge angle can be in the range of about 40° to about 45°.