How to sharpen a Forstner bit

Re: How to sharpen a Forstner bit

Barry Irby

There msut be about ten things sold as Forstner bits.

On the cheap ones I have that are coat with "Tin" I sharpened the inclined cutting plane that cuts the bottom of the hole with a diamond file. Mine have "saw teeth" that cut the perimeter and I touched them up with a diamond file also.

As for the cookie cutter rim....?....Maybe a Dremel with a conical diamond hone.

They're consumables; buy a new one

Re: How to sharpen a Forstner bit

John McGaw

I've touched them up with a diamond hone and with fine abrasive paper. Neither seemed to help that much or for long so they eventually get replaced.

Re: How to sharpen a Forstner bit

Bruce, a MN Galoot

Barry sez “As for the cookie cutter rim....?....Maybe a Dremel with a conical diamond hone.“

That’s what I do. It works pretty well.

Re: How to sharpen a Forstner bit

John in NM

I use a Dremel or Foredom tool with a little grinding stone for the rim. Even one of those sanding drums will do.

The rim is less crucial than the bevels, just needs to be sharp enough to make a clean side without burning. Main thing is filing the bevels nice and sharp. Other main thing is keeping the bevels even Don't want one cutting heavier than the other. Counting file strokes is enough to keep them even though.

A triangular file can't quite get all the way in next to the spur, so I do that with the Foredom too.

Re: How to sharpen a Forstner bit

William Duffield

I agree with Clint, but with some additional details. I started with the cheapest set of Chinese Forstner bits I could find. If I've used one enough to dull it, I go out and buy a Famag Bormax bit to replace it. I've never worn one of those out, not even my dog hole bit. If someone does a lot of kitchen cabinets with Euro hinges (I know you don't), then I would start with a carbide tipped 35 mm Forstner bit for that application.

Re: How to sharpen a Forstner bit

Rick W

My local sharpening service does a good job of sharpening them. I think it costs either $5.00 or $ 7.00 each. That's enough so I only sharpen the good ones, and I discard the cheap ones when they get dull.

Rick W