As with most types of fasteners, a wide variation of woodscrews is available with the most common types being a twin thread, chipboard, or velocity screw. Each of these types of screws is actually suitable for a large range of applications.
Twin thread woodscrews (both Pozi drive and countersunk) are a traditional woodscrew that gives rapid installation into softwoods. They are also an ideal choice for use with a plastic wall plug when fixing into masonry.
Chipboard woodscrews are best when used with softwoods, chipboard, plastics, and some hardwoods. Many builders and carpenters use chipboard screws as their “go-to” screw for general timber use.
Velocity screws are a premium multi-use screw that can be used with a range of materials including thin sheets, metal, PVC-u, MDF, softwood, and hardwood.
When it comes to the sizing of woodscrews it is still very common to find measurements in both metric and imperial. The diameter of a wood screw is either given in a gauge (imperial), or in millimeters (metric). With the imperial gauge, a number is used, i.e. 8 gauge. A larger gauge number means a larger diameter. Screw gauge numbers actually correspond to a particular fraction of an inch in imperial measurements.
Woodscrew lengths are also often shown in either metric or imperial, or sometimes both.