Abstract: A cutter bar with indexable blades for a rotary lawn mower which can be substituted for a conventional cutter bar in the rotary lawn mower and is replaceable and easily indexable without detaching the replaceable blade from the cutter bar or upending the mower. The cutter bar has a recess with abutment shoulders on opposite ends thereof for receiving the indexable blades, each such indexable blade comprising a plate with a plurality of sides sharpened into cutting edges and a socket with a hole for receiving the head of a bolt. Each recess in the cutter bar has a socket into which the socket of the indexable blade is fitted and a hole for receiving the shank of the bolt. The indexable blades are held in the recesses with a nut threaded on the bolt which is preferably a carriage bolt with means for retaining the nut on the shank when the nut is loosened.

Abstract: The burr formed on the breakout side of a workpiece during a drilling operation is removed by a deburring bit positioned underneath the workpiece in axial alignment with the drill bit. The drill bit is of the twist type and has at least two longitudinal flutes joined by a web and separated by an equal number of longitudinal lands. The deburring bit has a number of radially extending cutting elements which project radially outwardly from adjacent the bottom of each flute to substantially beyond the diameter of the hole. At the bottom of the flutes, the radially extending cutting elements are spaced to pass the web of the drill bit axially therebetween and to engage the flutes when the drill bit is rotated.