Sharpening a Forstner Bit

[glenn bradley]

I'm sure most of us on here know how to do this or have at least seen an article on it. Never the less, I am all finished picking up after the last project and this is on my list. I use a selection of tools based on the size of the bit. This bit is a 1" so everything should be pretty easy to see.

I use a paddle of some sort (diamond file, credit card, honing stick, whatever) to do the faces of the cutter.

I am holding this with one hand and snapping the pic with the other so you can see the rear of the face is slightly elevated. DO NOT do this. You want the face flat against the abrasive. Give an equal number of strokes to each face. I use a fine and an extra fine.

You will feel a bit of a wire edge as a telltale of your progress. I use a smaller file for the tooth in the rim. Your bit may not have a tooth or it may have many teeth. I use this same tool to refresh the center spur.

You want that leading edge nice and sharp.

For the rim I use a stone. The smaller the bit, the smaller the stone. It is easy for me to make a mistake on a smaller bit with a large stone and make a bunch of recovery work for myself.

I approach the bit like so for the inner edge of the rim.

I use a rolling motion to pass the full length of the inner face of the rim past the stone. Again, make an equal number of passes on each face.

I've almost got it. You can see a bit of area that I have not gotten to at the very edge of the rim. Once you are all sharpened up your bits will cut like new again

 

[Mike Stafford]

Years ago when I got my first set of Forstner bits (I think they were from Leichtung Tools) they came with a set of instructions for sharpening. I still have that set of bits and I still have the instruction although they are falling apart at the fold creases.

They follow your excellent instructions almost identically. I learned the hard way to use smaller stones. Sharpening the inside bevel of the rim is by far the most difficult aspect of the job. I have tried a lot of different techniques and none work as well as using a conical stone by hand which takes practice....a lot of practice.

 

[Jim DeLaney]

Years ago when I got my first set of Forstner bits (I think they were from Leichtung Tools) they came with a set of instructions for sharpening. I still have that set of bits...

That's where I got my first ones, too. I still have them, and after many sharpenings they still cut beautifully.
BTW, the bits were/are made by Fisch, in Germany, before they were known of here.

 

[Paul Douglass]

And I have always thought when the get dull you buy a new one... Got to try this,, thank you

 

[Jim DeLaney]

And I have always thought when the get dull you buy a new one... Got to try this,, thank you

Sharpening is fairly easy - once you get the knack for it.

If you're buying new, I'd suggest the Lee Valley Hi-speed steel ones. Good quality, and long lasting. Also available in metric sizes.

 

[glenn bradley]

Sharpening is fairly easy - once you get the knack for it.

If you're buying new, I'd suggest the Lee Valley Hi-speed steel ones. Good quality, and long lasting. Also available in metric sizes.

+1 My start with Forstners was probably familiar; an inexpensive high carbon steel set. This had two advantages; one, they were inexpensive and got me started using Forstners (which improved my woodworking) and two, they dulled with use so I learned to sharpen them. All my Forstners and Forstner-ish bits are now high speed steel. Most are from Lee Valley (use that wish list for these sorts of things ). These stay sharp much longer but sharpen the same way. I use diamond files now instead of steel bow-tie files.

 

[Frank Fusco]

Mine are all about a century old. Don't recall ever actually sharpening any of them. But I have touched up with a diamond paddle. If they ever need real sharpening I would do it by taking to the guy up the road who does it professionally.

 

[Jim DeLaney]

Mine are all about a century old.

Forstners, or augers?