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Odd Sized Screws and Screwdrivers

By: Chris Hogan MSc - Updated: 22 Sep 2011 | comments*Discuss
 
Screw Screwdriver Allen Key Screws

It might be surprising to know that there are many more types of screws and screwdrivers than the classic slot head screw or the Phillips cross head screw. In fact, you would be amazed at how many different types of screws and screwdrivers are out there, although if you’ve ever struggled with “self-assembly” furniture you will have come across some of them for sure. The average DIY enthusiast may never use most of the stranger screws and screwdrivers, but that does not mean they are not useful.

Bizarre screw names

Some of the different variations of screws and their corresponding screwdrivers include Tri-Wing, Spline drive, Triple square, Polydrive, and Pentalobular. If you’re new to DIY you may ask yourself why there are so many different variations of screws. The reason is that different types of screws are used for different purposes.

For instance, a One-way screw is often used for fastening car number plates because it cannot be unscrewed, and so deters people from removing them.

Back to more familiar screw types

For basic DIY jobs it is not really necessary to know about all the different types of screws and screwdrivers that have been developed. But apart from the common slot and cross head screws and screwdrivers, there are a couple more types that you should become familiar with to improve your DIY skills.

One type of screwdriver that you should get accustomed to is the Allen key. They are sometimes referred to as hex keys because they are hexagonal when viewed end-on. The chances are you may have used one before.

The cheap and flexible Allen key

It is a simple tool that is cheap and easy to manufacture, so they are commonly found bundled with flat-packed furniture, self-assembly office chairs and the like. Allen keys are L-shaped and either end of the Allen key can be used to tighten or loosen a hex screw.

This means that you have two options in restricted spaces, and as there’s no handle the screwdrivers are very cheap to make, making them the perfect choice for low-cost furniture manufacturers.

Using Allen-headed screws

The screw that is used with an Allen key has a head with a recessed socket in the shape of a hexagon. The technical name for this type of screw drive is the Hexalobular socket, but you are unlikely to hear this name being used. A correct sized Allen key should fit snugly inside the socket of the screw and if it does not, then you are most likely using the wrong sized Allen key.

Due to its design, an Allen key that’s too big for a hex screw socket will simply not fit. But if you use a key that is slightly smaller than the socket it can fit. It is important to remember never to use an Allen key that is too small for the screw that you want to tighten or loosen. Doing so will round off the edges of the Allen key and the screw’s socket, and could end up rendering them both unusable.

Torx screws – in your car and mobile phone

Another type of screw that’s in widespread use but often hidden from view is the Torx - this is a registered trade name. A Torx screwdriver can look very similar to a cross head screwdriver, but on closer inspection an important difference can be seen. Instead of the four points of a cross, a Torx screw driver has six points in the shape of a star.

Because a Torx screw has a corresponding six point star shape recess in its head they are sometimes called star screws. These types of screws are can be found in anything from a car to a mobile phone.

Non-slip applications

The reason for their popularity is the simple design which reduces the chances of the screwdriver popping out of the screw as you turn it. This makes items faster and cheaper to manufacture, with less wastage. The only problem with this is that it can lead to over tightening in comparison to standard slot and cross head screws.

Horses for courses

Choosing the right screw for your DIY project shows forward thinking and will make for a better end result. Allen keys and screws are great for things that you may need to dismantle in the future to move around, hence their widespread use with self-assembly furniture.

Torx screws are well suited to fastening something that should not need to be removed unless for essential maintenance. This is why they are often used in the construction of electronic devices. Both of them are also much more resistant to stripped heads than traditional slots and cross-head screws.

Take a look at strange screws

It’s worth expanding your knowledge of the different type of screws and screwdrivers out there. As your DIY skills improve and you embark on more specialist projects, may want to think about using a screw that suits what you are making.

But don’t worry too much about knowing about all the different types of screws and screwdrivers available to use, because for the majority of basic projects a simple slot or cross head screw will suffice.

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