Square Hole Size: 1/4 inch / 6.4mm, 5/16 inch / 8mm, 3/8 inch / 9.5mm, 1/2 inch / 12.7mm. Refers to the edge length of the square hole drilled by the square bit. Application: This mortising chisel is ideal for drilling square holes in wood with a mortising machine or mortising attachment. mortise. Suitable for use in the wood, construction, installation and decoration industries. Features: Reduce the labor intensity of construction workers, speed up the speed of construction. Material: high strength and hardness, made of high quality material, wear resistance and easy to use. Note: other dimensions are shown in the picture. Please avoid 1-2mm errors due to manual measurement. Product Item s: -Square Hole Size : 1/4 inch / 6.4 mm, 5/16 inch / 8 mm, 3/8 inch / 9.5 mm, 1/2 inch / 12.7 mm. Refers to the edge length of the square hole drilled by the square bit. -Application: This mortising chisel is ideal for drilling square holes in wood with a mortising machine or an accessory to mortise. Suitable for use in the wood, construction, installation and decoration industries. -Features: Reduce the labor intensity of construction workers, speed up the speed of construction. -Material: high strength and hardness, made of high quality material, wear resistance and easy to use. -Note: d other dimensions are shown in the picture. Please avoid 1-2mm errors due to manual measurement. Package: 4pcs Square Drill Bit Note: other accessories are not not included. Item Specifications: Drill Bit Material:Metal Clamp Shank Diameter:19mm/0.75inch