Recommendation? Bad Heat treat?

[Grayzer86]

One thing that gets overlooked is that there can be a few thousandths of an inch of decarb along the edge. A few passes on the grinder will take that off to good steel before you grind down to your final edge thickness. If you don’t clean this up, the edge will not hold beyond a few cuts.

Secondly, you didn’t mention geometry. What is the purpose of the knife, and who is going to use it? Most of my knives are under 0.010” at the edge before sharpening. I don’t do a lot of hard use blades, so slicing is what I prioritize. With simpler steels such as oil hardening tool steels and 10xx steels, 0.010” for general use is ok, and 0.005” for kitchen knives work well. With higher alloy steels such as z-wear, pd-1, cru-wear, 0.005” is the thickest I go. When I started making knives, 0.020” at the edge sharpened at 25dps was a common recommendation. That feels like a club to me know. My personal edc is 0.003” before sharpening at 10dps iirc. I’ve gone down to 5-6dps on a couple kitchen knives, and they cut!

This decarb issue is something that I didn’t think about and bit me on my first few knives years ago, so it’s entirely possible this could be part of the issue. I was confused about why they didn’t hold a good edge until I sharpened them a few times. Then it hit me, the edge is clearly decarbed too and needed to be ground back a bit.

 

[Willie71]

This decarb issue is something that I didn’t think about and bit me on my first few knives years ago, so it’s entirely possible this could be part of the issue. I was confused about why they didn’t hold a good edge until I sharpened them a few times. Then it hit me, the edge is clearly decarbed too and needed to be ground back a bit.

I had the same issue, but really noticed the light coloured edge on a W2 blade I did a hamon on. Then it clicked. I can be a bit slow sometimes.

 

[K7JDD]

Ok. Hopefully I am doing this right. Not sure if I should have started a new post. When I got home today I took my EDC out to the shop. It was so dull you could slice it on your finger pads and not even leave a mark. It sure looked sharp. I ground it back on the edge a little and then profiled it with a fresh Norton Blaze 120 on a 1x30. at 20dps. Then a couple passes on a 220, making sure not to overheat it. This is what I ended up with. First it raised a burr then the burr turned into a foil type edge. Soft and floppy. I ran it over a piece of balsa real light to remove it then stropped with green then red then leather. Once again, razor sharp for 3-4 good shaves/paper slices. Darn it. I realized that this knife probably just went from EDC to experiment. Bummer about the $25 stabilized Burl scales. Oh well. The nail chop results. No chip, just a bent divot. What does this all mean?!? Stop me before I ruin this next batch of steel!

 

[Grayzer86]

Could be soft from underhardening or over tempering. I would say at 20dps that edge looks incredibly thick based on the height of the sharpened edge. There is also a good chance you could be overheating the edge based on the belt speed of a 1x30

 

[K7JDD]

Could be soft from underhardening or over tempering. I would say at 20dps that edge looks incredibly thick based on the height of the sharpened edge. There is also a good chance you could be overheating the edge based on the belt speed of a 1x30

Thanks. I was thinking the same thing about the high edge. Is that a sign that I am not grinding my initial bevel properly? I am using 5/32nd steel. Maybe I need to get back to basics. I fear I may have thought I knew what I was doing when in fact I was making bum knives.

 

[Willie71]

I’m going to guess your edge was still at 0.050” or maybe a bit thicker based on the pic of the edge. You need one of these to measure edge thickness before you sharpen:

https://www.ebay.com/itm/12-Precisi...kproof-Mechanical-4-Way-Caliper-/231707843955

With the thickness you have, you won’t get a good slicing or cutting tool.

 

[joedhiggins]

Based on all the above, I am guessing your heat treatment is underhardened, owing to the lack of soak time. Also, your edge is way too thick, but your HT is what is causing the edge retention issues.

 

[joedhiggins]

Also, don't feel too bad about your previous work, you learn, and also, try doing a nail test with most mass produced knives on the market, and you won't be floored by the results.