What are the CNCs Best Router Bits and Uses?

Posted by John Rennie on

Whether you’re looking to intricately engrave a design into a piece of wood, or if you need to create precise drill holes on a piece of acrylic, you’ll need to choose the most suitable router bit for your CNC tool. Depending on your skill level, experience, and desired finish, this may mean that you need look at buying new router bits in order to complete the job at hand. 

There are many suppliers of CNC router bits in the UK, each offering a wide selection of products; so much so that being able to separate the good from the bad and finding the right solution for your project can be somewhat tricky. 

To help you find the best router bits for your needs, we’ve put together this handy guide on the most appropriate CNC router parts for every type of finish, ensuring you don’t waste money on an unsuitable router bit set, or worse yet, ruin a piece of material because the wrong bit has been used. 

Types of Router Bits 

Before we look at the types of CNC bits and the results they give, it’s first important to identify exactly what a CNC bit is. Generally speaking, there are two types of router bits: drill bits and router bits. 

Drill bits are used to make pre-drilling holes, but they’re also used when you’re working in lines that move through and down a piece of material. 

In contrast, router bits move across a material rather than straight through it, resulting in 3D finishes due to the lateral movement of the router bit. Router bits are also sometimes called end mills, cutters, and carving bits (a testament to their carving uses). 

Types of Cut 

When you use a CNC router tool, no matter what bit you use, you’ll be making one of three types of cut. The first is the up cut which refers to a router bit that pulls the material you’re cutting into up and out. This is the most widely used type of cut and leaves a very clean finish at the bottom of the cut. 

The next type of cut is the down cut which is the opposite to an up cut. This means rather than pulling the material chips out of the top of the cut, they are forced down and through the cut. This doesn’t work well on thick materials and isn’t recommended for drilling holes because the exit hole won’t be clean or refined. Down cut router cutters eave a very good, clean finish at the top of the cut.

The final major type of CNC router bit cutter is known as the up / down compression cut. They leave clean edges at the top and bottom of the cut because they are essentially a combination of up and down cuts. This means that whilst material is being pulled up, it is also being pushed down. Despite this, compression cut router bits shouldn’t be used to drill holes – there will come a point when the material chips can’t be pulled up and so will get pushed down, resulting in overheating and a poor finish overall. 

So, now you know the types of cuts CNC router bits make, let’s explore the best bits for different finishes and tasks. 


If you’re looking to engrave a material at a surface level, you’ll need flat bottom bits. They are sometimes also called cylindrical router bits and there are differences between those used to engrave metal or plastic and wood. In essence, as the name suggests, flat bottom bits have a flat end. This allows real precision and accuracy when engraving. 

Routing Channels 

There are many instances when you may need to create a routing channel in a material – typically wood. Ball nose bits are ideal for this because the arc shaped tip creates smooth channels ideal for making juice channels in chopping boards and the like. 

Relief Carving 

Relief carving is incredibly intricate and produces 3D designs on flat panels of wood. It gives the illusion that the design is separate to the piece of wood it’s on, and this high quality finish is achieved using tapered ball nose bits. If you need a CNC router bit to carry out relief or projection carving, you’ll need a tapered ball nose bit. 

Hard Material Cutting 

Do you need to cut through something like hardwood, fibreglass, or even carbon fibre? If so, you’ll need a corn teeth end mill router bit. Specifically designed for hard surfaces, this end bit will allow you to cut and mill with relative ease. 

Drilling Holes 

If you need to drill a hole, make sure you use a specialist CNC drill bit. They will create the cleanest cut and ensure the bit doesn’t get overheated due to improper use. 

How to Use Router Bits 

If you’re new to working with carbide CNC router bits, you need to ensure you’re fully familiar with how to use the bits before you start out. This will prevent breaking or damaging the tool and material at hand, but it will also ensure you’re following proper safety protocols to avoid injury. For more information, read our guide on how to use a router tool

Buy CNC Router Bits 

Rennie Tools is a leading UK supplier of router bits, providing high quality, reliable carbide bits. You can order the bits you need online, with purchases over £30 qualifying for free UK shipping. We also ship worldwide, so no matter where you are, you can find the right tool for your project. 

If you need help choosing the right bit, please either call us on 0161 477 9577, or email us on esales@rennietool.co.uk.

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