Forstner bits

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Forum topic by Monte Pittman posted 02-22-2013 01:11 PM 1182 views 0 times favorited 8 replies Add to Favorites Watch
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Monte Pittman

30153 posts in 2579 days

02-22-2013 01:11 PM

Topic tags/keywords: question

Is there any good way to sharpen them. None of my local guys will touch them.

-- Nature created it, I just assemble it.

8 replies so far

View bondogaposis's profile


5155 posts in 2592 days

#1 posted 02-22-2013 01:18 PM

They are easy to sharpen. Watch.

-- Bondo Gaposis

View cutworm's profile


1075 posts in 3034 days

#2 posted 02-22-2013 02:19 PM

View Kazooman's profile


1270 posts in 2193 days

#3 posted 02-22-2013 02:42 PM

I don’t like the method in the second video. I would avoid touching the front bevel of the cutter just as the guy in the first video suggests. I would clean off any pitch or other residue, but beyond that messing with the front edge is asking for trouble. Those edges should be perfectly perpendicular to the shaft of the bit and they should be at the same depth. Using the Dremel tool runs the risk of messing up one of those properties and then you could have just one blade cutting or just a portion of a blade cutting.

View paratrooper34's profile


915 posts in 3192 days

#4 posted 02-22-2013 04:45 PM

Monte, I agree with Kazooman, the second video shows how NOT to sharpen a forstner bit. When you sharpen these types of bits (including the self-feed types), you only sharpen the flats on the angled part of the bit, just as seen in the first video. When you sharpen the flats on the bottom, you risk changing the geometry of the bit. As you see in the second video, he sharpens the area on the inside perimeter of the bit, but the rotary tool does not sharpen all the way to the edge. This leaves a small portion of that area slightly longer. When you move to sharpen the flats on the bottom, you effectively change the depth of that area in relation to the small unsharpened portions on the perimeter. That will then leave you with a bit that will not cut because the small portions that are deeper on the perimeter will not allow the cutting surface on the flats to actually reach the wood. If you only (correctly) sharpen the angled area, you will not change the depth of the bit.

Hope that made sense. Good Luck!

-- Mike

View tefinn's profile


1222 posts in 2678 days

#5 posted 02-22-2013 06:38 PM

I use these to sharpen my forstner bits.

They do a really nice job on the smaller ones. Takes a little longer on the larger ones where a diamond card would be faster.

-- Tom Finnigan - Measures? We don't need no stinking measures! - Hmm, maybe thats why my project pieces don't fit.

View pudtiny's profile


21 posts in 2202 days

#6 posted 02-23-2013 07:29 PM

This is how I do mine: please note some of the useful comments.


View Roger's profile


20965 posts in 3045 days

#7 posted 02-23-2013 11:51 PM

Good post Monte… and, Thnx for all the links from ya’ll.

-- Roger from KY. Work/Play/Travel Safe. Keep your dust collector fed.

View Monte Pittman's profile

Monte Pittman

30153 posts in 2579 days

#8 posted 02-23-2013 11:53 PM

I have diamond blocks on order as we speak

-- Nature created it, I just assemble it.

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