Professional wood drill bit, suitable for construction, installation, renovation, decoration, etc. The piece forms a hole drilled by the rotating body, while the impact of the use of impact force is transmitted to the outside of the body, the material creates a round hole and a square head, all at once, and the dust can be discharged through the tube.< /p > Professional design ideal for drilling square holes in wood with a mortiser. Fits all drill machines and attachments. The square hole drill bit is mainly used in the woodworking field. Material and size: Made of high speed steel. Heat treatment, HRC48~ 50, high hardness, elongated center, high concentricity; 4 sizes 1/4" (6.35mm), 5/16" (7.94mm), 3/8" (9.5mm), 1/2" (12.7mm). Reduced labor intensity of construction workers while accelerating work speed and reducing cost. Perfect for the construction, renovation and decoration sectors. 1 piece 1/4" (6.35mm), 1 piece 5/16" (7.94mm), 1 piece 3/ 8" (9.5mm), 1 piece 1/2" (12.7mm)