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Sharping carbide on a CBN wheel

T

Tim Thor

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Jan 18, 2012
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Concord, Ca
I am planning to make a shear scraper from a triangular carbide paint scraped blade. I am wondering if it ok to use a CBN wheel to sharpen the carbide cutter. I am thinking that the CBN should be able to handle it but wanted some input before I ruined the CBN.
Thanks for any thoughts.

Tim
 
I don't own a CBN wheel, but it's my understanding that CBN wheels will sharpen carbide. However, the life of the wheel will be significantly shortened. The best for sharpening carbide is still a diamond wheel in my opinion. I bought diamond wheels for my Tormek because the Tormek gouge jig will also sharpen some carbide insert cutters (like round Easy Wood cutters). I would check with a repurtable vendor who sells CBN wheels, like Sharpening Supplies (sharpeningsupplies.com). The have been very helpful answering a variety of sharpening questions related to the right stones and wheels.
 
Ruin a $150 or $200 CBN wheel to sharpen a $7 piece of carbide? What is that cutter 3/4 inch on a side? Be careful of those points.
 
No, don't do it. As said before, it will GREATLY shorten the useful life of your CBN wheel. Best for sharpening carbide is diamond. Diamond wheels do not work well on even our slow speed grinders because any heat at all will cause the diamonds to break down. There are diamond wheels for the Tormek and other clones of it. With the water and slow speed, they should last forever.

DMT does make diamond lapping plates up to 8000 grit. No clue as to how fine you need to go to improve the edges on your diamond cutters.

robo hippy
 
I ground a 1/2" Hunter cupped carbide cutter in half. I'm talking about grinding off 1/4 " of nano carbide on a 180 grit CBN wheel. Did not hurt it at all. I ground a negative rake on a flat Easywoodtool carbide cutter, just because. Still didnt hurt the wheel. I reground the tip of a solid carbide milling cutter. Still no damage. So I would say yes you can. At least until someone can prove me wrong.
Now to sharpen all those flat carbide cutter you dont want to hollow grind them. I think your much better off using a flat diamond lapping plate. You cant sharpen the cupped cutters. So there really isnt a reason grind a carbide cutter on a CBN wheel.
 
I can't remember, but I think I had some carbide brazed onto my McNaughton blades. I tried to touch them up on my CBN wheels, and the wheels were never the same after. If I had the flat carbide cutters, I would maybe touch them up on a diamond wheel for the Tormek. Not sure if the fine grit plates from DMT would help them or not.

robo hippy
 
john lucas said:
I ground a 1/2" Hunter cupped carbide cutter in half. I'm talking about grinding off 1/4 " of nano carbide on a 180 grit CBN wheel. Did not hurt it at all. I ground a negative rake on a flat Easywoodtool carbide cutter, just because. Still didnt hurt the wheel. I reground the tip of a solid carbide milling cutter. Still no damage. So I would say yes you can. At least until someone can prove me wrong.
Now to sharpen all those flat carbide cutter you dont want to hollow grind them. I think your much better off using a flat diamond lapping plate. You cant sharpen the cupped cutters. So there really isnt a reason grind a carbide cutter on a CBN wheel.
Click to expand...
Hollow grind? I would think you'd use the side of a wheel to sharpen a flat carbide blade. I think I've even seen a video of this on a CBN wheel.
 
I had some old articulated head hollowing set up that had a HSS cup cutter. They supplied a small mandrill with a screw in the end so you could mount the cup on the mandrill, put it in a drill, and spin it against a wheel or diamond card.

robo hippy
 
I tried sharpening Hinter cutters using a jig like Reed suggests. It didnt work. The hunter cutters just chip with every thing I have tried.
 
Well, trying to figure out why they chip. Carbide is prone to chipping especially if you go against some thing hard. I wonder if you could try stropping it? Polishing compounds up to 15000 grit, on leather, a soft wood, even MDF. It might work. If I was going to polish on a diamond card, I would use VERY gentle pressure. I would think that both the inside and outside would need polishing. Always some thing new to try...

robo hippy
 
Reed I tried polishing compounds from RioGrande.com. The finer ones won't remove enough metal to sharpen past the chips in the edge. The courser ones created more chips. Probably needs some kind of machine to control the force and speed rather than rotating the tool by hand against the abrasive. Anyway as it works out the Hunter cutters hold an edge long enough it's really not worth trying to sharpen them. I have 2 cutters that are on my ornament hollowing tools. I have probably hollowed more than 200 ornaments with them and they are still cutting well. I clean up the bottom of all my boxes and deep bowls with the Hunter Badger which is my oldest Hunter tool. I've only changed that cutter once. I got that tool shortly after Mike started making tools so that tells you how old it is.
 
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Of course you can grind carbide on a CBN wheel. But that doesn't mean it's a good thing to do in terms of the longevity of your CBN wheel.

Precision grinding of carbide inserts needs a rigid, non hand held method. Diamond wheels are the best method. And composite diamond wheels that can be dressed to run true are far and away better than plated wheels to get the razor sharp edge that micro grain carbide is capable of.
 
Perhaps it is my Grandma's influence on me that causes me to shy away from 'disposable' items. She lived through the Great Depression, and she never wasted anything. The cup type cutters like Hunter, are probably very delicate and can't be done by hand. It would be interesting to see the manufacturing process....

Doug, I am curious about your comment about preferring the composite diamond wheels. I had a composite CBN wheel a couple of years before the plated ones were widely available. I don't think it was even close to the overall performance of the plated wheels, both for running true and for not loading up. Getting the sharpest edge on the carbide tools may be more technical than most of us can expect to be able to do. I guess if I wanted a diamond wheel for trying to sharpen the carbide cutters, I would look to the Tradesman grinder and set up. They started out as a sharpening system for the CNC machines.

robo hippy
 
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