Carbide Tear Out with KME Stones

[tomhosang]

Hello everyone! I've had my KME system for a while now and have 50 knives or so under my belt. I've had excellent results for the most part but have had some issues recently. I use my 100 grit stone for reprofiling and just had to order a new one because I wore out the old one. I've sharpened 4 knives on the new one and have had the same issue on every knife. Once I get to the higher grits, I notice some shiny, rough spots on the edge. It is still sharp on that part but not as sharp as it should be. The knives were all S30V and 20CV which are higher carbide steels, so I'm wondering if what I am seeing is carbide tear out since the stone is new and quite aggressive? Is there any way I can combat this until my stone breaks in a bit? I don't remember having this issue with the original 100 grit stone. I also am noticing some very small chips in the edge occasionally when sharpening. Any help would be appreciated. Thanks!

https://imgur.com/gallery/kOAQL

 

[jpm2]

I don't think you can see carbide tear out without a microscope. I don't think you can even detect it with sharpness tests. I do think where it can be detected is how long the edge lasts.

What you're seeing there seems to be from the coarse stone. Continue with the finer stones until it disappears. Once the new stone breaks in, the problem should go away.

 

[Lapedog]

Hello everyone! I've had my KME system for a while now and have 50 knives or so under my belt. I've had excellent results for the most part but have had some issues recently. I use my 100 grit stone for reprofiling and just had to order a new one because I wore out the old one. I've sharpened 4 knives on the new one and have had the same issue on every knife. Once I get to the higher grits, I notice some shiny, rough spots on the edge. It is still sharp on that part but not as sharp as it should be. The knives were all S30V and 20CV which are higher carbide steels, so I'm wondering if what I am seeing is carbide tear out since the stone is new and quite aggressive? Is there any way I can combat this until my stone breaks in a bit? I don't remember having this issue with the original 100 grit stone. I also am noticing some very small chips in the edge occasionally when sharpening. Any help would be appreciated. Thanks!

https://imgur.com/gallery/kOAQL

Try putting water with some dish soap on the diamond stones when using them and use less pressure, especially as you are refining the apex.

 

[Mo2]

Don't apex with the 50 or 100 grit stones. They are way too coarse to apex and will cause issues in later grits. They are great for hogging away material when re profiling.. Dean O on YouTube did a video on this.

But anyways because they are too coarse it tears the edges out if you apex. Then when you goto the next stone that edge damage is seen even more.

Edit : it was Jay Davis that said it but referenced in a dean O video here. Skip to 8min into the video and soon after he talks about it around 9min mark when he takes a microscope to it.

 

[jpm2]

Here's a sage1 fresh off a Norton jb8 coarse side (background). Some say it's 100 grit, some say 120. Whatever the case, it can finish with a very useable edge, although not near as good as a 250 grit diamond plate.

Most diamond plates come pretty ragged new, they need broke in before attempting to apex. Got a spine to work down? Maybe thin some bevels? Shorten a blade? Reshape a handle?

 

[Student762]

mmm, Ya need to break that bad boy in mate, just to echo the sentiments of every poster who's come before me.
Break the stone in and don't apex with something that rough.

 

[tomhosang]

Thanks guys, I really appreciate it! Some extra work with the 140 fixed it right up.