Can CNC Bits Be Sharpened?


Bits are responsible for the bulk of the output you get from a CNC machine. They can shape and add character to any surface, but only when they are sharp. Dull bits can burn materials and make a project more laborious than it should be, so can you sharpen your CNC bits?

Most CNC bits can be sharpened, especially carbide-tipped variants. However, spiral bits are best sent to a professional to avoid ruining them. For DIY CNC bits sharpening, you should avoid using files and whetstones as they can disrupt the bit’s balance. Diamond stones work best when used carefully.

The rest of the article will look at how to sharpen CNC bits the right way and what to expect when you take your bits to a professional service.  Of course, handheld router bits can be sharpened the same way.

Why Sharpen CNC Bits?

CNC bits need to always be sharp because it’s the only way to ensure a clean cut and avoid excessive strain on your router. For example, if you are a woodworker, dull CNC bits will leave unsightly burn marks on your wood, leaving you to spend a lot of time sanding the wood down again. Keeping your bits sharp will help ensure better use of your time, avoid excessive downtime, repeat work, that will reduce your profits.

Sharpening the bits is also a good way to ensure it reaches and surpasses its lifespan. Waiting until the bits start to show signs of bluntness is detrimental to your setup. You should schedule regular cleaning and sharpening–especially if you work with the tool regularly.

Cleaning CNC Bits

Before you start thinking about sharpening your CNC bits, it’s always a good idea to clean them out first. In some cases, a proper wipe down can get your bits working great again. Look for any good blade solvent to remove resin, pitch, and other impurities that may be responsible for the dull edges on the bits. 

Some handheld router bits include guide bearings that also need to be maintained and cleaned.  If your bit has guide bearings, make sure to properly lubricate the bearing after cleaning.

How Can You Sharpen CNC Bits?

Usually, CNC bits are sent to industrial sharpening centers to be reground and given a fresh edge. However, you can achieve similar results (and save time) by using diamond hones to sharpen the bits on your own, as they have the hardness required to sharpen carbide.

Honing is also safer for the integrity of the CNC bits compared to grinding because it removes a thin layer of material. This also allows you to hone as regularly as necessary to maintain sharpness.

When sharpening a CNC bit, the area of attention is the cutting edge, which is the intersection between the beveled profile and the flat face of the bit. If this edge is sharp, it will look like a uniform and one-dimensional line. As the bit loses sharpness, the edge will wear down, giving you a third “face.” This new face will create smoke, heat, and unwanted marks you’ll see on the material’s surface as you work.

To sharpen the bit quickly, you need a 45-micron coarse hone and water as a lubricant. Put the carbide’s flat face against the hone, stroking carefully until your cutting edge looks like a thin line again.

You need to stroke each flat face on the CNC bit the same number of times as the others to maintain the bit’s balance. Round off the process with a 25-micron hone to get the edge looking sharp.

This process will work if you have high-speed steel or carbide bits.  However, it’s rarely a good idea to sharpen all kinds of spiral CNC bits at home with the method we’ve discussed. It’s easier to damage the balance and make the bits less responsive.

Sharpening spiral bits even at industrial sharpening centers may also not be the best approach if you can get some new ones at a discount. This is because paying for the sharpening can cost 25-50% of the price of brand new pieces.

You should also keep in mind that the diameter of any CNC bits sharpened (either with a diamond hone or at a shop) will reduce slightly.

What Happens When You Send CNC Bits to a Sharpening Service?

We talked about spiral bits as the variants that should go to a professional sharpening service. Still, even with other bits that you can sharpen at home, there’s always the risk of disrupting the bit’s balance and making it less precise—which can cause more serious damage to your router. Sending the bits to a sharpening service is the best approach to take when you’re not sure.

Remember that the bit diameter will change slightly after being sharpened. If your CAM software calculates the tool path based on the bit diameter, It is important to remeasure the bit and enter the new value into your software.

Steps of a Professional Sharpening Service for CNC Bits

Firstly, the best services will understand the value of a sharp CNC bit to your business and will work to meet your unique demands. This ensures you have sharpened bits that won’t feel out of place on the surfaces you usually work on.  The process will start with proper cleaning and inspection, followed by regrinding the bit while maintaining shape accuracy as closely as possible.

Once the bit ticks all the right boxes, it will be packaged and sent back to you. The length of the process will vary from one company to another, so don’t forget to get estimates so you can adjust your work deadlines as necessary (or seek replacement bits).

When choosing a service, ensure they have worked on your variants of CNC bits before. Modern router bits look different from older ones because the former now come with opposing shears, different shear angles, special coatings, extra wings, and hi-density formulations. These changes mean that you have to choose a company with the right knowledge and tools to maintain your router bits’ features.

How To Maintain Router Bits After Sharpening

Whether you’re a hobbyist or a professional, you should maintain your router bits to keep them working longer before losing sharpness. Proper maintenance also helps you get a high-quality and clean cut at all times.

Keep Them Clean

Keeping your CNC bits clean can improve the lifespan a great deal. You can clean them with WD40 or denatured alcohol. These cleaning agents can get rid of most built-up residue. You can also prevent rust and discoloration by rubbing some machine oil on the bits after cleaning.  If your handheld router bit has ball bearings, use an air gun for cleaning instead of solvents to avoid stripping away the lubricating oils and damaging it.

Always Use the Right Bit

There are dozens of router bits meant for different jobs. You should ensure you’re always using the best one for a project to avoid wasting money on new bits and risking damage to your engine. For instance, carbide-tipped bits are not meant for working on ferrous metals. Using bits that are too big for the job can also damage the router and the project. It’s, therefore, in your best interest to work with the right bit on every project.

Avoid using your CNC bits on a drill press as the spin is far too slow for a router bit. Also, don’t forget to change the router’s speed to match the bit size you’re using.

Store Them Properly

Storing the router bits the wrong way can make them lose sharpness as fast as wrong usage. You shouldn’t throw them in your toolbox with other materials as this can dull the edges and increase the chances of corrosion. You’ll also end up buying bits you already have by mistake. Get a holder that has room for each bit, so you can find any of the pieces when you need them while also preventing constant friction.

Conclusion

You can sharpen most types of CNC bits with a diamond hone. However, the task of DIY sharpening is not for everyone. Don’t hesitate to send the bits to a sharpening service if you’re unsure about completing the process properly to avoid wasting time and money.

It’s also a good idea to sharpen the bits fairly regularly instead of waiting until they are completely dull.

Sources

John McCormick

I have been woodworking since being introduced to the hobby in High School. I enjoy woodworking as a hobby and would like to share some of what I have learned with the world. I have recently built a CNC router system and I have enjoyed learning this new dimension of the hobby.

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