6 Reasons Why CNC Router Bits Burn Wood and How to Fix It

It is disappointing when you think you have done everything correctly, but the router bit is still burning your wood. This burning can create a charred or dark marking on your woodwork (that will be difficult to remove) and can even result in material wastage, thus degrading the workpiece quality. 

So here is a comprehensive guide to the prominent reasons behind burn marks created by CNC router bits and the top ways to fix them.


Top 6 Reasons Why Your CNC Router Burns Wood and Their Solutions

1. Very high speed

Extremely accelerated router bits could produce wood-searing heat way too quickly. The trick here would be to accurately manage the rotational speed of your router bit based on its diameter. 

One needs to learn about the wood material workpiece as some types of wood may not burn rapidly due to their density and the contained oils and extractives. As a result, dense woodland necessitates slowing the router and increasing the feed rate to reduce burning and vice-versa.

2. Too slow pace

In contrast to the first point, slowing down when using a wood router can also result in wood burning. To prevent heat generation that induces burns, feeding the stock as quickly as practical without leaving chatter marks is the ideal solution.

A low feed rate quickly generates greater heat. Use a quick and steady feed rate to keep the router a bit cooler. Always adhere to your wood router's instruction handbook for the appropriate speed. Also, consider your router bit diameter when determining the ideal speed.

3. Dusty build-up on router bits

Resin and dirt accumulation leads to rapid heating of the router bits as they spin, causing them to burn the wood. Thus, wiping the router bits and cleaning the entire router with a dry cloth and a blade and bit cleaner after every operation is crucial. Cleaner bits retain their sharpness as cleaning minimizes the amount of superfluous heat underneath the carbide cutters.

4. Heavy passes

A thorough and heavy pass eliminates a lot of material, but it can also lead to the burning of the wood. Thus, ensure the wood router has been removed with little exceeding 0.125 inches of material remaining for each pass. Most of the latest routers include sharp carbide-tipped bits capable of making large cuts.

The ideal step is to measure the amount of wood that needs removal. If it's larger than 1.25 inches, just make several shallow passes. So, rather than one deep entry, make two or three passes.

5. Dull router bits

Bits that have been refurbished or rehappened are less precise since they have lost their initial cutting edge. Because of their inefficiency, they cut badly and can generate a lot of heat.

You can use diamond stone grits to refine the cutting edges of the bit. But keep count of your strokes on either side to ensure that you eliminate an equivalent volume of material. Alternatively, have an expert sharpen the bit or replace it.

6. Faulty configuration of the router bit

Wood burning can also be caused by loosened or inadequately placed router bits since, based on its position, the bit could have a lower or high feed rate, which can create heat generation.

Thus it's critical to install the router bit in the tool properly. You must place the shank entirely into the collet, then slightly draw it out to prevent bottoming out the bit. It also ensures that the collet grips the bit securely.


Top 4 Ways to Fix CNC Router Bit Burn Marks on Wood

1. Hand Sanding

It is the most prevalent approach for removing CNC router bit burn marks. Starting with sandpaper or block, gradually work with the grain.

Sand cautiously enough to just eliminate the burn mark. If the dry technique isn't working, you can apply a little moisture to the burn mark. It will elevate the grain and allow the mark to be eradicated.

2. Recurving

It is the most preferred technique if you have adequate material to return to the workpiece and re-carve the routed edges or pattern. Nonetheless, this may not be a practical solution because the resources are limited after the initial carving is made on the CNC.

3. Multiple routed passes

If you are short on time and realize that your CNC router bit will produce a burn mark on the wood, you can carve lesser material or create multiple passes on the wood. It produces a better setting for you to create a superior routed carve free of router burn marks.

4. Using hand planes

Several woodworkers and furniture manufacturers prefer to reduce burn marks with a hand plane since it is more efficient and faster. You can erase burn marks with a smooth plane, a block plane, or indeed any hand plane. A few moderate passes will be required to fix the burn marks. Perhaps, you may want to confine it to small planes because they are convenient to hold in your hands.

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CNC router bit burns are troublesome and can cost you big bucks if you have to buy additional material and resources and reproduce the wood designs. But simple preventative maintenance practices, such as routine cleaning and repair, can eliminate the primary cause of burns and heating.

Finally, assuring that your CNC routing bits remain sharp and that you are using the appropriate feed rate and chip load will help avoid CNC routing bit burns.


About the Author: Peter Jacobs

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