What is square hole drill? A square hole drill, often referred to as a mortising bit, is a specialized tool used to cut square or rectangular holes, commonly in wood. The most common example is used in mortise and tenon joinery, a traditional woodworking method for joining pieces of wood.

　　How does a square hole drill work? Here’s how it works:

　　1. Hollow Chisel and Auger Combination

　　The square hole drill consists of two main components:

　　- Hollow Chisel: A hollow, square-shaped chisel with sharp edges on all four sides.

　　- Auger Bit: A spiral drill bit that runs through the center of the chisel. It acts like a regular drill bit to remove the material.

　　2. Operation Mechanism

　　- The auger bit first starts drilling a round hole into the material (usually wood), removing the majority of the material.

　　- As the round hole is drilled, the square chisel presses into the wood around the hole. The sharp edges of the chisel cut the wood at the four sides of the square, shearing off the corners and shaping the hole.

　　3. Mortising Machine

　　Square hole drills are usually attached to a mortising machine, a stationary power tool specifically designed for this purpose. The machine pushes the drill and chisel down into the wood while the auger bit spins.

　　4. Result

　　The result is a clean, precise square hole, which is difficult to achieve with conventional round drill bits alone. This method is especially useful for woodworking joints, such as mortises for fitting tenons.

　　In summary, the square hole drill works by combining a rotating drill bit (auger) to remove the bulk of the material and a fixed square chisel to shape the hole into a square.