A screw is never just a screw. There are, in fact, several different types of screws, each specially designed for a particular job and for use on specific materials. Most types of stainless steel screws are very easy to tell apart, as their shapes, lengths, heads, threads and points (or lack thereof) give them away. There are, however, two particular types of screws that are not so easy to tell apart: sheet metal screws and wood screws.
Just a thread apart
Obviously the main difference is that one is used for wood and the other is used for sheet metal, but how are they designed for these differing purposes? At first glance, they do look very similar and they both come in the same variety of heads, ranging from flat to round or oval, with Philips, straight or square driver slots. So how do you spot the difference?
The visible difference is in the thread. Woods screws have a wider-spaced, medium-depth screw. Some wood screws – longer ones – often have a threadless shank at the top of them. Sheet metal screws, on the other hand, always have a tighter, sharper thread that cover their entire length.
These screws are not really interchangeable. In a bind, if you’re short of the right available screws, you can use a sheet metal screw on wood. However, the opposite is not the case. Wood screws are unlikely to form a tight enough joint when used on sheet metal – especially if they have a threadless shank.
The simple answer is always to ask for the right types of screw for the job you are doing. If you are unable to visually tell the difference between wood and metal screws, your hardware dealer or fastener supplier will be able to tell you. For the best quality stainless steel screws of any variety, pay a visit to Marsh Fasteners.