Why Is My Router Bit Burning the Wood? (+ 3 Simple Fixes)

Router bit burning marks can be quite frustrating, especially if your project is nearly completed.
If you want to stop the router bit from leaving black marks on your routed edges, there are some simple actions you can take.

  • Check if the RPM of the router is too low or too high
  • Clean dirty router bits
  • Sharpen your router bit
  • Take smaller steps while milling
  • Install the router bit at the correct dept and make sure it is secured in place
  • Use a proper feed rate

Burn marks on the wood will differ per type of wood, but in many cases, it is also human errors that cause burn marks.
With burn marks, many will find their workpiece worthless and throw it away. In short, that means wasted money and time.

But it doesn’t have to come to that. Thanks to this article, you will gain a clear insight into what you can do to avoid burn marks, but also how you can avoid burn marks if they are created while working with the router.
So if you no longer want burn marks on your wood, read every letter of this article.

Disclosure: At zero cost to you, I may get commissions for purchases made through links in this post. I earn from qualifying purchases as an Amazon associate. Products featured are selected based on quality, performance, and reputation, regardless of affiliate relationships.

What causes a router bit to burn wood?

While working with a woodworking router, black spots may suddenly appear on the wood. Therefore, it is best to study them and find out what could be the cause. Black spots on the wood during milling can be due to various causes, but also a combination of several unfavorable things. To understand why a router burns wood, the following things can be checked:

The router bit speed is too high.
Router bits spinning too fast can generate heat so quickly that the wood will burn. The black spots from a router bit spinning too fast will show up the entire length of the edge. The key here is to control the speed of rotation correctly depending on the diameter of your cutter.

The router bit speed is too slow.
Unlike a router bit spinning too fast, a slow pace when using a wood router can also lead to wood burning with similar symptoms. In the case of burn marks that can be found over the full length of the processed piece of wood, this will therefore indicate an incorrectly set speed.

Dirty router bits.
It may seem strange, but dirty router bits will cause burn marks, and that’s totally understandable.
The accumulated dirt or resins on the router bit will cause the bits to get hot faster during rotation, as a result, the wood will burn.

Blunt router bits.
To get a perfect finish, it is best to work with sharp router bits. When a router bit is blunt, a lot more heat will be built up due to the poor cutting of the wood, resulting in burn marks. What’s more, poorly cutting router bits will put more stress on the router itself, resulting in faster wear and tear. You will also find that you will have to put in more effort to push the router bit through the wood.

You take too heavy steps.
The more wood you want to remove in one pass, the greater the heat that is built up between the router bit and the wood. Most modern routers have sharp carbide bits that can make huge cuts, but too big will undoubtedly cause burn marks.

Incorrect bit installation.
A loose or incorrectly installed cutter can make off-center turns and generate more heat. This not only causes burn marks on the wood, it is also a dangerous situation. The router bit can come loose, break off and fly off at high speeds up to 35000 RPM.

The feed rate is too low.
Of all the tips above, this is undoubtedly one of the most common causes of router bit burning stains. Many people think that a modest feeding rate will yield better results. This is not the case! With a rotating router in the same place on the wood for a longer period of time, more heat will be generated. Even a small interruption in the grinding process can lead to burns.

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How to stop router bits from burning wood?

Now that you know all the causes that result in router bit burning marks, it is easy to find the right actions to solve this problem.
For each possible cause, you can find below which adjustments you have to make or what you can take into account so that you are sure of a clean workpiece without burn marks.

Increase or decrease the cutter’s speed.
Most routers currently feature variable speeds that allow you to match the RPM to the cutter diameter and the wood you’re working with. It’s normal to want to use a faster RPM. In my article, What Is The Best Speed For Router Bits? (Router Speed Chart), I go over how to figure out which speed is the right one. This is a must-read article!

Remove the router bit and clean it.
The buildup of residue on a bit’s cutting edges lowers its cutting effectiveness. As a result, clean the router bit on a regular basis to remove any dirt. To do so, you’ll need a router cleaner that won’t harm the carbide. Below is an illustration of this cleaner from CMT.

CMT Formula 2050 Blade and Bit Cleaner

Check out more details and prices of this product by clicking the link below.

Regularly sharpen the router bit.
The wood will be burned if the cutter is dull. Sharpen the router bit on a regular basis, even if it appears to be sharp. Sharpening not only assures a sharp cutting edge, but it also allows for the removal of minor flaws.

Sharpening bits on a regular basis will also help them last longer. If you wait too long between sharpenings, you’ll need to grind away additional carbide to restore the cutter’s cutting edge.

Sharpening a saw blade or a router bit is not the same as sharpening a chisel’s bevel. Milling cutters have a complicated cutting geometry that can be easily destroyed if the surfaces are ground freehand. As a result, I advise that this work should be done by professionals.

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Take several steps instead of one heavy step.
Earlier in this article, you could already discover that one reason for burned wood was that too much wood is taken away at once. To avoid burns, it is best to cut the profile in two or more passes.

With the first pass, you can make a heavier cut that already forms the profile well. However, keep a close eye on the cut and make sure that no combustion occurs and that the speed of the router is maintained.

If there is a small burn, you can remove it in a second or third pass. The last pass is a very light cut where a perfect and smooth profile can be obtained without burn marks.

Check the installation of the router bit.
Before you plug in the router and start it, always check if the router bit is installed at the correct depth and secured in place, so it won’t loosen while milling.

Increase the rate of feed.
Going faster with the router over the wood will prevent the router bit from turning too many times on the same plate and generating heat, which can cause burns. Don’t go too fast, though; the router bit needs time to cut into the wood. Listen closely to the router’s noises to ensure that the motor is “singing” and running properly.

How to avoid a router bit burning MDF?

Using a router bit on MDF can lead to burn marks pretty easily. To avoid this, you need to understand why this happens.

Is it OK to Use A Router On MDF?

This should be the first thing you should ask yourself if you start on any task, not only on routing MDF.

MDF (Medium Density Fiberboard) is a high-quality, low-cost building material. It does not split or crack like plywood because of the rich mix of wood fibers and resin.

But is it OK to use a router in this hard material?

In a nutshell, yes, you can use a router on MDF. The type of cutter you employ is the most critical factor to consider. A solid carbide router bit produces the best cutting, but carbide-tipped router bits can also be used.

This type will easily cut through those dense MDF wood fibers due to the many cutting edges. The right type of router bit is the first step to avoid burn marks on MDF.

Is MDF bad for router bits?

MDF contains resins and makes fine dust. This is the ideal combination to blunt the sharp blade by sanding, but also by sticking to it and contaminating it.
So, if you regularly use a router bit to work on MDF, you will have to take the time to clean them well.

As a result, the router bit will last much longer and cause fewer burn marks on MDF.

You will see that when milling in MDF, the router bit will be dirty faster. It is therefore very important to pay extra attention to this point.

Furthermore, you will have to apply all the actions you could read earlier in this blog to avoid burn marks on MDF.

How to avoid a router burning plywood?

Plywood, especially birch plywood, is prone to burn marks. I like the aesthetic of birch plywood, however, using a router bit can result in annoying burn marks.

Plywood is made composed of multiple glued-together thin layers of wood. It is more sensitive to burn marks than solid wood because of the thin layers in the wood. Because of the grain orientation, you’ll notice that certain layers are burned darker than others while looking at burn marks. Long grains are more resistant to burn marks than cross grains. This is also true with solid wood.

In order to avoid burn marks with multiplex, I have already found that the most important factor appears to be the depth of the router bit. The more wood you remove in one pass, the higher the risk of burn marks.

So be careful and remove the wood in several small steps. Of course, it is good to take into account all the other tips that you could read earlier in this article.

How to remove router burn marks from wood?

Making test cuts in advance can ensure that you can make small adjustments to prevent burn marks. However, it can still happen that you get burn marks while milling. Then you should, of course, try to get rid of the burn marks, otherwise, you may end up throwing your workpiece away.
But don’t panic right away. If you do have a burn mark, then I have 3 very simple solutions for you.

Router bit burning removal technique 1:

If it’s only minor burn marks, a simple piece of 220 grit sandpaper may suffice.
But beware, sanding a profile is not without its dangers! Sanding paper that is too coarse or sanding in one place for too long can cause you to deform the profile. So be careful when you start working with sandpaper and only use this technique with very light burn marks.

Router bit burning removal technique 2:

For dark burns, try scraping them off. And what is the best scraper for this? Your router bit itself, of course, because it has the shape of your profile!
To make scraping easy, first slightly wet the place where the wood has burned. Apply some water to the tip of a cloth or a cotton swab and massage the burned spot. This makes the wood softer, but it also swells slightly. Now you can scrape the wood with the blade of the router bit until the burn mark has completely disappeared.

Router bit burning removal technique 3:

For very heavy burn marks, you can opt to make a new light cut with the router bit.
To do this, shorten the edge of the wood slightly by making a few passes with a hand planer or passing it along the table saw blade. By making the edge a fraction smaller, the router bit will remove a very thin layer from the profile with a clean and burn-free surface.

This technique is not suitable for all situations because you make the surface of the wood slightly smaller. A slight adjustment of your workpiece can already ensure that it no longer fits nicely in your project. In that case, you will have to switch to one of the two techniques mentioned above.

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I hope this information on how to avoid router bit burn marks on wood was helpful, and that this blog inspires you.

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Christophe, founder of Christofix.com
Woodworking | DIY | Home decoration

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