Figure 1 - Parts of a wood screw
All wood screws are made up of three parts, as shown in Figure 1.
The difference between a traditional wood screw and a modern wood screw is the relationship of the outside diameter of the shank to the outside diameter of the threads.
With a traditional wood screw the outside dimension of the shank is the same as the outside dimension of the threads, as shown in Figure 2.
In a modern wood screw the outside dimension of the shank is the same as the inside dimension of the threads, as shown in Figure 2.
Figure 2 - traditional versus modern screw diameters
Why is the difference in shank diameter relative to the thread diameter important?
There are two reasons:
- When drilling a pilot hole for a traditional wood screw, you should drill a different size hole for the area that will be threaded than for the area that will contain the shank portion of the screw.
- There is less binding between the wood and the shank with modern wood screws than with traditional wood screws.