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.
Pilot holes for modern wood screws.
Pilot Hole Size For Traditional Wood Screws - Inches & Millimeters.