【High Quality Steel】This square hole drill bit is made of special steel, heat treatment, HRC48-50, providing high hardness, elongated core, and high concentricity. Sharp blade, continuous, fast cutting, high efficiency. 【How to do the job】: The square drill bit enters the drilled hole of the rotating body, while the impact force is transferred to the outer body, grinding the round hole and square head wall of the material, and the debris will be discharged from the pipe at the same time. 【Labor-saving and Precise】: This professional mortise chisel is ideal for drilling square holes in wood with a mortising machine or mortising attachment. And reduce the labor intensity of construction workers, speed up the construction speed, reduce construction costs for construction, installation. 【6 Different Sizes】: 6 pieces in the package with different groove diameters to meet your needs. Comes with 6 different sizes: 1/4 inch 5/16 inch 3/8 inch 1/2 inch 9/16 inch 5/8 inch, suitable for opening various square holes. 【Application】: Fits all mortising machines and drill attachments. Square hole drilling is mainly used for aspects of woodworking. Professional tip, suitable for construction, design, renovation, decoration, etc. Note: The chisel does not work alone in a wood drill, you need an attachment for your drill.