The principle of a chisel and bit is that the bit sits proud of the chisel by a couple of millimetres and drills a circular hole, closely followed by the chisel which slices four corners into the hole, leaving a true and precise square hole. These premium mortice chisels and bits are made from a special grade of high carbon steel which is extremely hard wearing and retains its hardness over prolonged use, resulting in a chisel and bit that will not deform under heat and which will always keep the same cutting geometry, over its lifetime.
The body of the chisel is CNC ground and fractionally back tapered from the cutting edge to reduce friction and prevent binding. The four points of the chisel are hardened and razor sharp and slice into the wood, leaving a clean sided hole. The Japanese pattern bit has precisely ground cutting tips and spurs which are designed to break the swarf for fast chip ejection. This prevents the bit from clogging in the chisel and allows for fast morticing operation.
The window of the chisel should always face in to the previously cut mortice to aid chip removal. These are premium performance chisels that will leave a clean, flat sided, square mortice in both hard and softwoods.