I have a carving knife, that has a full flat grind. I took it down to about 20 thousands then heat treated it in a Paragon Oven. The steel is CPM 20cv at .095. I used the direction that I found on the steel manufactures web page. I used the oil quench method. This is my question. I tested the cutting edge using a piece of 1/4 inch hot rolled round rod.. I held the knife at and angle and pressed down hoping that it would not snap and that it would flex back. It did not snap or chip, but it did not flex back. It left a little dimple. I did this test after I finished grinding the full flat edge. Can this knife be saved. If so I would love some help from you guys on how to do it. I have a hardness tester arriving at the end of this week and will test the knife. I do not think that it will do me any good to know the hardness at the handle when the edge is the problem. One thing that I may have done was overheat the edge when I finished the grind. I do know that it was hard to grind after hardening. I am hoping to learn from this mistake, when someone one here point it out. Thanks.
Edge test using a 1/4 in round rod. Did not flex back.
- Thread starter kammphoto
- Start date
These are only guesses but might be a place to start in figuring it out.
1. The edge test is mostly about looking for chips and seeing how a slight (the width of the sharpened edge) will handle a side load. You may have pushed a bit too hard. It happens.
2. The edge could be quite soft from too high of grinding temps, especially on a thin edge like a kitchen knife. Make a pass, dunk to cool, make a another pass.
3. Testing the hardness on the handle will at least tell you most of the heat treat went well...or didn't. You won't be able to test edge hardness since material needs to be flat.
good luck. I hope you figure it out.
t
1. The edge test is mostly about looking for chips and seeing how a slight (the width of the sharpened edge) will handle a side load. You may have pushed a bit too hard. It happens.
2. The edge could be quite soft from too high of grinding temps, especially on a thin edge like a kitchen knife. Make a pass, dunk to cool, make a another pass.
3. Testing the hardness on the handle will at least tell you most of the heat treat went well...or didn't. You won't be able to test edge hardness since material needs to be flat.
good luck. I hope you figure it out.
t
Self Made Knives
Well-Known Member
If you did get it too hot, just a little at the edge, you might be able to grind back about 1/16" or so and get back into good metal. But like Boss said, before I did anything I would want to know the hardness at the riccaso or handle.
Thanks guys. I think that I was pressing a little bit hard for what the knife will be intended for. I will also cool the blade after every pass. I was not doing that. I will take the edge back about a sixteenth and go from there. I have a couple more questions. When I test the hardness and say that it is around 59-60HRC, can I anneal the steel and then start the heat treat for hardness over again? I have ordered some s90v at .075 thickness and will be making the same kind of knife and some fillet knives out of it. Would it be possible to completely finish the grinding before heat treating? I would still like to have a full flat grind. With the CPM 20v I was worried about the warping and left some extra steel on the edge. That did not make any difference, the steel had a good sized curve to it when I put it into the oil. ( The overall length of the blade is 14 inches.) With the s90v I will be air quenching between 2 pieces of aluminum. I hope that this will somewhat keep it straight. I was also wondering when is the best time to straighten out a warped blade. Thanks
rhinoknives
Well-Known Member
Just to make sure, When you say you did the test against a 1/4" round rod. You do mean brass, right?
It was not brass. I thinks it is just hot rolled A36. I think that you you guys are correct, I believe that the blade was getting hot while finishing the full flat grind. I ground the edge back some, and I think that it is a little better. I was trying to get more out of the belt than I should of. Lesson learned. I just received my CPM S90V in .075". This time around, I will take more time and keep the blade cool. I am still not sure if I should finish the full flat grind before heat treating or after. Anyone's input would be welcome. Thanks again.
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