Fixings 101 – The Basics of Wood Screws

Screws are important through bolts used in carpentry. The use of these through bolts is mainly to join two pieces of wood together to increase the thickness of the wood and so that the strength of these two pieces would be added together.

There are many types of screws and they are classified in four ways: the type of drive, the shape of the head, the shank of the screw, and the size of the screw. Each kind of screw serves its own purpose.

Wood Screw Fixings by Drives

When we talk about screws and classify them by the type of drive that they have, we would be talking of only two things. One is the slotted drive type of screw, whilst the other would be the Philips type of drive.

The slotted drive type has a single hollow bar straight across the head of the screw. The Philips drive, on the other hand, has a cross-shaped slot on its head. Because of the shape of this slot, the Philips drive is also called the crosshead drive.

A variation of the Philips drive is the Pozidrive screw. Like the Philips drive, the Pozidrive also has a crosshead, but on all the angles created by this cross, a tiny corner juts out.

Wood Screw Fixings by Heads

We can also classify screws according to the shape of their head. Under this classification, there are three types of screws – countersunk heads, raised heads and round heads.

screws with countersunk heads are made for concealment. They are screwed tightly into the surface of the wood, where they can appear “invisible.” The raised head screw is also good for concealment but they are not as “invisible” as the countersunk-headed screws. That is because the raised head is slightly domed and can be seen on the wood.

The round-headed screw, on the other hand, is not meant to be invisible. Its large head rests in a dome right on the surface of the wood.

Wood Screw Fixings by Shanks

The shank of the screw refers to its tapering tail. All screws, regardless of their classification, have only one single appearance to their shanks – they are tapered. This tapering shank differentiates screws from screws used on metal. Screws for metal surfaces always have parallel shanks.

Wood Screw Fixings by the Size

screws are also classified according to their sizes. These sizes are determined by the length of the screw and its gauge number. The length of the screw can be measured easily – all you need to do is to apply a ruler and measure its length from head to tip.

Getting the gauge number of a screw is another matter. If you do not know the gauge of the screw through bolts that you need, then you may need to do a bit of math. Put a ruler to the diameter of the screw’s head and convert that measurement to the sixteenth of an inch. Subtract one, and then multiply the remainder by two. Whatever number you will get will yield these fixings’ gauge numbers.