The differences between self-tapping, self-drilling and CSK screws

When it comes to screws, there’s a lot of choice. And with so many different and similar names, it can be confusing to work out which is which.  

This is especially the case with three types of screws in particular; self-tapping screws, self-drilling screws and countersunk screws, otherwise known as CSK screws.  

Self-tapping and self-drilling screws are both designed mainly for metal, whereas a CSK screw is designed for timber to steel or any other metal. As such, it’s important to be clear with what you’re using.  

In this article, we will explain what each of these three screws do, to clear up any confusion. We also have a video on the topic, which you can see below.  

Self-tapping screws 

Self-tapping screws are perhaps the most easy to mistake, as they look very similar to a wood screw given the thread goes all the way up. However, there are several key differences between the two.  

The centre shank of the screw is a lot stronger and heavier than a wood screw, which is the first giveaway, while the thread pitch is also a lot closer together.  

In addition, a self-tapping screw is very tough as it would’ve gone through a strengthening process before leaving the factory. 

As for what it does, a self-tapping screw makes its own threaded hole as it’s driven into a material. It doesn’t need a pre-drilled hole, which can make it very convenient.  

Self-drilling screw 

As the name suggests, self-drillers – or TEK screws, as they are referred to– are designed to drill their own hole and then tap their own threads as it’s driven into the material.  

They have a completely different front compared to self-tapping screws, with the front designed to act like a drill. A self-driller will then pre-drill through the material, before then bringing the thread in behind it.  

This is otherwise known as drilling and then tapping, so it’s easy to see why there could be some confusion with self-tapping screws.  

However, a self-drilling screw is a more technical screw and is made up of multiple different parts. This in itself should help differentiate it from a self-tapping screw.  

Countersunk screws 

The first thing that sets a CSK screw apart is that it is designed for a completely different material than both the self-tapping screw and the self-drilling screw.  

They have a countersinking head, but also have two small bumps on either side, which are located shortly above the drill point. These are sometimes referred to as wings. 

The purpose of these bits is to clear out the timber as the screw goes through the material, which prevents it damaging the thread.  

Once they reach the metal point, they snap off and then allow the screw to tap into the metal material, making it a very effective screw.  

Brilliant options for brilliant projects 

All three of these screws are highly beneficial when used properly, but using one in an instance where another should’ve been used can end badly.  

Hopefully we have helped clear up any confusion around the screws, whether it’s from this article or the video at the top of the page.  

If you would like to speak to someone at Multifix about any of these screws, we are happy to help. You can get in touch with us via this link.