Abstract: A cartridge just large enough to hold a cutter tooth and a setscrew. The cartridge has an open-sided tap for the setscrew, exposing part of a side of the setscrew. A cutter body has a slot to receive the cartridge. The slot has a leading side with a generally cylindrical smooth wall portion that surrounds the exposed side of the setscrew. The cylindrical concave portion is uniquely angled to wedge the setscrew firmly against the cylindrical concave portion as the setscrew is tightened, and to force the cartridge against the bottom and trailing side of the slot. The cartridge and slot have parallel interlocking interfaces on both their leading and trailing sides. These are slidable interlocks, allowing the cartridge to slide into the slot while engaging both the leading and trailing interlocks. The setscrew can easily be manually tightened while the interlocks hold the cartridge steady in the slot.