Professional wood drill bit, suitable for construction, installation, renovation, decoration, etc. The workpiece forms a hole drilled by the rotating body, while the impact of the 'use of percussion force is transmitted to the outside of the body, the material creates a round hole and a square head, in one go, 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. Square hole drill bit is mainly used in 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 the labor intensity of construction workers while accelerating the speed of work and reducing costs. Perfect for the building, 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)