Do You Sharpen Forstner Bits?

If you don’t currently sharpen forstner bits, I would highly recommend that you learn how. There’s some good benefits for learning to do it.

You’ll save so much money and time when you learn the basics, trust me it’s not difficult to do. It’s so much cheaper to learn the technique than going out and buying a replacement forstner bit or having to pay someone to sharpen them for you.

The tools that you need to sharpen them is also talked about in this writing. Plus they don’t cost a ton of money and besides whatever you spend on sharpening tools will pay for themselves over time.

Can You Get Forstner Fits Sharpened?

The good news is that they can be sharpened. There are two different ways of sharpening forstner bits which are discussed below. With a little bit of practice and patience you’ll find that it’s more beneficial to you to learn how to sharpen them yourself.

Should Forstner Bits Be Sharpened?

I would encourage anybody that uses forstner bits to learn how to properly sharpen them. These boring bits can get pretty expensive, even the cheaper ones. Plus the bigger the bit the more expensive they are.

Sometimes the forstners that you buy aren’t really as sharp as they should be so you might as well learn how to use a file and or a credit card diamond stone. Besides, learning how to do it properly isn’t that difficult and it doesn’t take that much time. 

You’ll save yourself time from making multiple strips to the store to buy new forstner bits. Also think of all the money that can be saved by learning this easy technique.

Cleaning Forstner Bits

No matter what kind of forstner bits you have and there are multiple ones, make sure that they are clean before starting the sharpening process. Clean off all of the sap and debris left behind from use.

A good product to use for cleaning forstner bits or any other woodworking bits is a tool cleaner called Trend CLEAN/500 Tool Cleaner Industrial Strength Wood and Resin Remover.

It’s safe to use while at the same time removing sap from the surface. It also helps protect the bits from surface rust when not in use.

Forstner Sharpening Kit

If you’re sharpening different types of forstner bits by hand, you’ll need a forstner sharpening kit that can sharpen different kinds of bits. There’s a pretty good sharpening kit called TREND DWS/KIT/C The Complete Diamond Credit Card Sharpening Kit.

What’s included in the kit is a diamond file that’s 600 grit. The file has a flat surface that’s used for sharpening forstner bits that have teeth. The other side of the file is rounded or concave. This side is used to sharpen the wavy rim forstner bits.

The kit also comes with lapping fluid that’s used for lubrication when sharpening. A credit card sized sharpening stone which is double sided. On one side you have a 300 grit surface while on the other side is a 600 grit surface. 

The kit also comes with a cleaning block to keep your sharpening stone in good working order. They even threw in a non slip mat for the credit card shaped stone so it’s not sliding all over the place when you’re trying to sharpen your bits. A dvd also comes with the kit to show how everything works.

This kit can also sharpen different types of woodworking bits such as router bits, small chisels, woodturning gouges and carbide inserts.

Tips on Sharpening Forstner Bits

There’s just a couple of tips to help you with the sharpening process. When sharpening a forstner bit that has teeth: 

  1. Only file the flat of each tooth and always count the number of back and forth strokes with a file so that each tooth gets exactly the same amount of attention.

Don’t sharpen the sloping top surface of the teeth. This ensures that all of the teeth engage the wood at the same time so that they can all work together.

  1. Don’t apply a whole lot of pressure, you don’t want to remove too much material. 
  1. When filing across the cutting part of the bit you want to file at a diagonal motion so that the entire part of the plane is filed evenly.

Sharpening a continuous guide rim forstner bit is a bit different since they don’t have teeth but instead a wavy pattern:

  1. If using a file, use the rounded or convex side of the file. The rounded side will get the entire cutting edge sharp but the flat side won’t.
  1. Apply consistent pressure on the file. 
  1. Continuously keep moving the file around the inside of the guide rim. 

Best Methods for Sharpening Forstner Bits

There isn’t a best method for sharpening forstner bits. What it all comes down to is what kind of forstner bit do you have or plan on buying?

If you plan on buying just the ones that have teeth then the method is very simple. The file method and a little lapping fluid is the way to go.

You don’t need to buy an expensive forstner sharpening kit like I mentioned in the Forstner Sharpening Kit section of this article.

An auger file will do just fine for these types of bits.

The other method of getting forstner bits sharp is through the use of a dremel. This method is best used when you have continuous or wavy patterned forstner bits. You still have to use a file to get the actual cutters of the bit sharp though.

How to Properly Sharpen A Forstner Bit With A File

Steps for forstner bits with teeth:

  1. Put a little bit of the lapping fluid on the flat side of the file.
  2. Lay the flat side of the file up against the flat of each tooth.
  3. Then give the teeth 5 back and forth strokes with the file.
  4. Once the teeth have been sharpened take the same flat side of the file and go across the cutters in a forward and diagonal motion five times. 

Steps for forstner bits with a guide rim

  1. Put a little bit of the lapping fluid on the round side of the file.
  2. Firmly hold the bit by the shank with one hand or clamp the shank in a vice between 2 pieces of wood at an angle that is comfortable to work with.
  3. Place the rounded edge of the file on the cutting edge of the forstner bit.
  4. Using back and forth strokes continually move the file around the inside edge of the cutting rim.
sharpening a forstner bit with a file

Sharpen Forstner Bits With A Rotary Tool

Sharpening forstner bits with a rotary tool or dremel is a lot like using the file method. You still have to count your strokes on the parts to be sharpened. The rotary tool method will only work on the types of forstner bits that have a continuous guide rim. 

To do this properly you need to have:

  1.  a fine grit cone shaped stone for the dremel.
  2. Turn on the dremel and lightly grind on the cutting surface at the correct angle. At the same time keep the dremel stationary and rotate the forstner bit with your other hand
  3. Lightly grind on the flat cutters of the bit with the same amount of passes that you did on the guide rim. 
sharpening a forstner bit with a Dremel

References:

show how to use a Dremel for sharpening a forstner bit.