Highest quality hollow square mortise chisels and bits, made in Sheffield England. This tool is made with a 5/8"diameter shank and an 8" overall length. Correct setting of the bit in the mortise chisel will ensure successful cutting of the tool and to ensure long life. Place the chisel into it's socket in the attachment. 

Put a coin about 1/16 inch between the face of the socket and the shoulder of the chisel to prevent the chisel being pushed fully home, tighten down screw to hold the chisel in place. Now fit the bit into the chuck and push it as far as possible into the chisel and secure. Slacken off the screw holding the chisel, remove the coin, push the chisel fully home again, and tighten the screw again. This method allows sufficient clearance for the bit to run smoothly in the chisel and begin to cut just ahead of the chisel.