The form of the screw has a deep fine blade which is machined right to the end of the screw. This allows an easy lead into the wood and the depth of the blades and core size means that the larger wood blanks can me mounted onto the chuck.
The screw has a square shank for positive locking into the chuck. The screw is 23mm (15/16") long, with blades 2mm deep, and the core size is 7mm. All this adds up to a screw with a very powerful gripping action. The RH Woodworm Screw comes standard with the Nova Chuck, and with the SuperNova Standard and Premier versions.
Hole size for Woodworm Screw - The 10.5mm thread of the woodworm screw requires a drilled hole about 8mm (5/16") in diameter. The screw has considerable holding power and it is sometimes difficult to unscrew, so wax or oil the thread before mounting the wood.