What Type Of Router Bit Should You Get For Flattening Slabs?

Flattening Slab

If you are a passionate woodworker, you know how your mind leaps with joy and becomes filled with excitement when you find the perfect wood slab. To explore so many creative possibilities with one wooden slab, you jump to start preparing it. But before sanding and finishing your newly acquired slab, you need to first flatten it to perfection.

This flattening process is a vital job a woodworker has to go through regularly. And even though there are several tools available for the job, CNC machines and routers are two of the most popular ones. However, you need to make sure you are using the best quality router bit to accompany your tools.

There are several factors to consider when deciding what type of router bit for flattening slabs you need for your project. The bit has to be sharp, with a carbide tip, about ⅛ to 2 inches in diameter, the correct shank size, durable, and wear-resistant.

Here, we will discuss how to find the right type of router bit for flattening slabs so that you can create the best woodwork projects. But before that, let’s get to know flattening router bits a bit better. 

What Is A Flattening Router Bit?

Basically, a flattening router bit is a detachable component you use with a machine for flattening a piece of wood slab. You can buy these bits separately, for both CNC machines and routers, from hardware stores or online.

When you buy or collect a wood slab, it may come with uneven surfaces and rough edges. Such spots need to be completely flattened before using it for a project. Otherwise, the final outcome will have an unfinished appearance.

This flattening task can be performed with machines such as a planer, CNC, and routers. Being more precise than other options, CNC machines are the most popular among professional woodworkers. On the other hand, DIYers prefer routers more as they are inexpensive. Since both are versatile tools, they require different bits for different tasks. To flatten a wood slab,, you need to use a flattening router bit. 

Flattening Slab
Flattening Router Bit

What Type Of Router Bit For Flattening Slabs Should You Get?

As we have already mentioned, you need to consider a number of factors before selecting the correct type of router bit for flattening slabs. Using the right router bit will not only produce the best output but will also make the flattening process much easier and more time-efficient.

Flattening Slab
Type of Router Bit

Consider the following factors before getting and using flattening router bits.


Naturally, the first thing to consider is the sharpness of the router bit. If the router bit is not sharp enough, your wood slabs will not be perfectly flattened. By using router bits with dull blades, you bear the risk of ending up with uneven surfaces, even more than before sometimes. 

Tearout is another result of using dull router tips. When the blades are not sharp enough, they tear the wood fibers rather than cleanly severing them. Thus, you end up with an awful rough surface. 

Therefore, check the blades carefully. Professional woodworkers recommend router bits with carbide tips. A carbide tip has more refined grains in its construction, allowing it to be sharpened to a finer point. 

Bit Size

Getting the right bit size is crucial when deciding what type of router bit for flattening slabs you should get. If your router bit is too small, you will not get a clean cut, and it will also take too much time and effort to flatten a slab. On the other hand, if your router bit is too large, it will be difficult to control and may cause the wood slab to chip.

Flattening Slab

Therefore, you need to choose a router bit that is neither too small nor too large. Seasoned woodworkers recommend a bit size of ⅛ to 2 inches for flattening and surfacing a wood slab.

Collet and Shank Size

Next, look at the shank sizes of the router bit and the collet size of your machine. Based on the type of machine you are using, you will have different collet sizes to install your router bit. You will need to match the router bit’s shank size to the machine’s collet size. 

For example, if you are using a hand-held router for flattening a slab, the collet is likely to be of a smaller size. Therefore, you need to get flattening router bits with a small shank. Conversely, if you are using a router table for flattening your wood slab, get a router bit with a large shank, as the collet here is likely to be large as well.

Build Material

The build material of a flattening router bit is important for two reasons – to assess its quality and prevent injury. Router bits are usually made of high-speed steel and carbide. Carbide-made router bits are of two types: carbide-tipped and solid carbide. 

High-speed steel-made router bits are inexpensive but not very effective on the hardwood. Therefore, you should not use them for flattening slabs. A more expensive, durable, and effective option is using carbide-tipped router bits. We have already discussed their sharpness. Lastly, solid carbide router bits are the most expensive and durable, but they are not suitable for flattening purposes.

A flattening router bit with a fine-edged carbide tip is usually considered to be a high-quality bit. Such router bits minimize the risk of kickback. When a dull router bit gets stuck in wood, it struggles to continue cutting. When it is spinning inside, the energy will be transferred back to the router and then to the user’s hands. Thus, a serious injury may occur. Therefore, you need to ensure the build material of your flattening router bits is strong and sharp enough to work on solid wood.

Type of Wood

As we have mentioned, high-speed steel-made router bits are for softwoods, whereas carbide-tipped and solid-carbide bits are for hardwoods. Therefore, the type of wood slab you are working on influences your decision regarding choosing the right type of flattening router bits. If you use the wrong type of router bits for your wood, you will end up with a botched job. 


Usually, a flattening router bit can also plane and surface a wood slab. Some router bits are also capable of working on a range of materials, such as softwoods, hardwoods, MDF, particle boards, laminate, plywood compact panels, and acrylic. Getting these versatile router bits will allow you to get the best value for your investment in them.

Wear-Resistance and Heat Resistance

A brand-new, high-quality flattening router bit is generally sharp and stays like that for a good while. But, after months of use, it will start losing its sharpness. Although it can be resharpened, once it starts wearing out, it rarely can perform as well as it did. Therefore, make sure the flattening router bit comes with excellent wear-resistant construction. Luckily, carbide-tipped blades have wear resistance. 

Furthermore, keep the heat resistance of the router bit in mind. If your router bit overheats, it can cause serious damage to your wood slab, the machine, your workstation, and even your physical well-being. Therefore, make sure you get a flattening router bit with a heat-resistant Teflon coating.

How To Install A Flattening Bit On A Router?

Just like any other router bit, you can easily install a flattening bit on a router. Follow the steps below.

  1. Take the router body out of the base.
  2. Unplug the router and unscrew the collet from the motor shaft.
  3. Clean out debris from the shaft and the collet if there is any.
  4. Attach the collet back to the shaft.
  5. Insert the bit shank all the way into the collet.
  6. Carefully pull the bit shank back out about an eighth to a quarter inch.
  7. Tighten the collet keeping the bit in place.
  8. Put the router body back into the base.

How To Use A Router Bit For Flattening Slabs?

First, position the slab in the sled and on the table. Then start by running the router over the highest points of the slab. On each level or pass of cutting, keep adjusting the cutting depth and continue the process until the surface is completely and uniformly flat. Then flip the wood slab over and repeat the process. Take your time and have patience during the flattening process. After you are done, use sandpaper or hand plane to smoothen out the rough edges. 

Flattening Slab
How to Use a Router Bit for Flattening Slabs

Tips For Making The Best Use of A Flattening Router Bit

All the information above will help you decide what type of router bit for flattening slabs you need for your project and understand how to install and use it. While working with flattening router bits, follow the tips below to ensure safety, a clean workstation, and the best output.

  • Use a dust collector.
  • Align the fence and base plate properly.
  • If possible, perform flattening jobs on a router table to ensure safety and precision.
  • Try to apply even pressure everywhere when flattening a wood slab. 
  • Do not force the router bit to work on a material it was not designed for.
  • Keep it unplugged when not in use.
  • Keep your hands and cloth away from the router bit when working.
  • During the process, wear safety goggles, gloves, and hearing protection.

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