Stop the Smoking
So you've got a Forstner bit that you've been using for a while. It's causing more and more mess with untidy bores, and straggly bits of wood. Perhaps it's even smoking while you press it against the wood, a tell-tale sign of the bits failing.
Well, there are two solutions to this.
Either one, you stop what you're doing and go buy another bit, meaning you'll have to put the work down for an hour or so. Or more practically, you can put the work down for ten minutes while you sharpen the bit from the comfort of the site you're working on or your workshop.
How to Sharpen a Forstner Bit
We're going to take a look at some of the techniques you can use to resharpen your Forstner bit. Allowing it to cut clean, consistent holes with the same accuracy as when you first got it.
The sharpening tool we're going to be using in this guide is the 3" diamond sharpening taper file. It has the perfect grit for sharpening woodworking bits which is 600 grit. Anything more than 600 will be too fine, causing the blade of the bit to change shape and become thinner as a result.
It's also possible to do this using a credit card stone.
A Few Things to Note
When sharpening your Forstner bit, use as little pressure as possible.
Let the taper file do the work. We do not want to remove any material while honing the blades of the Forstner bit. Doing so will result in an altering of the size and radius of the bit. So light, even, and consistent strokes along the edge of the blade.
Consistency is Key - Saw Tooth Rims
When sharpening a Forstner bit that has saw tooth rim guides it's important to go round each one individually. Count each time you go through with the file, and keep that number the same for each tooth.
Depending on your cutter you can also sharpen around the centre point of the bit.
Although it's more important to focus on those blades that are just below the centre point, the radial edges. These blades create the flat bottom of the hole you are boring. To sharpen these you simply take the file and go under the blade.
This allows you to effectively hone the blades. All you have to do is bring the file in-line with the gradient like so;
Then gently stroke up into the blade a few times.
Again, not a lot of force or time is needed as you do not want to remove the material from the bit.
And that's what makes resharpening a Forstner bit so easy. You're not trying to remove any material from the cutter rather, simply giving a new bite to the teeth and an edge to the blades.