Confused with why my edge is rolling

E

emjay

Joined
Nov 27, 2012
Messages
171
A few years ago I made a knife from O1 tool steel. I heat treated it in the BBQ, quenched it in canola oil when it was ready and tempered it in the oven at about 220 deg Celsius (approx 430 deg Fahrenheit) for an hour twice if I can remember correctly. Of course this heat treating method is not going to be great and is not precise, but I'm just giving some background information

The thing is that's baffling me is that the edge rolls when cutting up veggies such as onions, carrots and potatoes, yet doesn't roll when I cut up chickens, going through the cartilage, breast bone and rib bones, nor when I use it on wood or purposefully whack it into the plastic chopping board or laminated kitchen counter top (did it to see if the edge would roll). I've edge tested the section of the blade that rolls by cutting sisal rope and cardboard until it no longer slices paper and got about 120 cuts on the rope and 130 feet of cardboard, which is in line with how O1 should perform apparently. No edge damage was noticed after testing it on the rope and cardboard, it just lost its paper slicing ability but still had an OK working edge on it. So according to the edge tests, the heat treatment went OK, but why does the edge roll when chopping up veggies? The veggies are clean and have no dirt on them when cut so that can't be it. I've whacked it into the plastic chopping board much harder than the force using to slice veggies with no edge rolling, so the chopping board isn't the culprit either.

I should note that it is dead easy to get a razor edge on it using stones and steels back to a razor sharp edge quickly after rolling, but it doesn't really feel gummy on the stones.

It's very confusing...
 
Did you say you heat treated it in a BBQ? Like, a cook-a-steak, BBQ? If so, I think I know where you might have gone wrong.
 
What happens to the edge if you do an edge flex test against a brass rod or sharpie pen?
 
DevinT said:
Poor heat treatment, most likely overheated before quenching.

Hoss
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Makes sense. No precision when it comes to temperature control in a BBQ
Drew Riley said:
Can you elaborate on the "BBQ heat treat".
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Heated it up in a charcoal fire to the point where it was just past cherry red, stuck it in canola oil and afterwards tested it with a file to see if it hardened. It looked like it did harden
HSC /// said:
What happens to the edge if you do an edge flex test against a brass rod or sharpie pen?
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Never heard of the sharpie pen test but when I draw the edge along a bronze brazing rod (I don't have any brass around), it passes the test. No edge deformation. Edge bends and goes back to true along the whole edge
 
emjay said:
Makes sense. No precision when it comes to temperature control in a BBQ

Heated it up in a charcoal fire to the point where it was just past cherry red, stuck it in canola oil and afterwards tested it with a file to see if it hardened. It looked like it did harden

Never heard of the sharpie pen test but when I draw the edge along a bronze brazing rod (I don't have any brass around), it passes the test. No edge deformation. Edge bends and goes back to true along the whole edge
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Sharpie pen is in lieu of the brass rod. You can use the body of the pen. That’s all. Or a bic lighter body.
 
Could be that the high light conditions when barbecuing meant the cherry red you were seeing was quite a bit hotter and further along the colour scale. This kind of inspection is best done in a darkened environment.
With this said I don't think it explains why you're experiencing edge rolling from soft materials but not on harder materials and I don't think any heat treat bungle could lead to that making sense. Take a step back away from the "I am experiencing edge rolling" conclusion and maybe something else will pop up that makes more sense.
 
Without seeing pics it's hard to know what kind of rolling you are getting on veggies, but is it possible you are seeing a wire edge from sharpening that rolls over? Because if you had a wire edge but chopped something hard, it would get flattened or knocked off and you wouldn't see it -- but cutting veggies it would fold over and still be visible. ??
 
Kailash Blades said:
Could be that the high light conditions when barbecuing meant the cherry red you were seeing was quite a bit hotter and further along the colour scale. This kind of inspection is best done in a darkened environment.
With this said I don't think it explains why you're experiencing edge rolling from soft materials but not on harder materials and I don't think any heat treat bungle could lead to that making sense. Take a step back away from the "I am experiencing edge rolling" conclusion and maybe something else will pop up that makes more sense.
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Heat treatment was done in the early evening, so I'm confident that I got the colour range right. Honestly through edge testing it seems like the heat treatment was done as right as could be done with primitive equipment, so hence my confusion. Maybe there is something in the chopping board that is causing the edge to roll, even though it is plastic. Edge rolling doesn't happen on my Victorinox kitchen knives during the same type of use though, so again, confused
 
fishface5 said:
Without seeing pics it's hard to know what kind of rolling you are getting on veggies, but is it possible you are seeing a wire edge from sharpening that rolls over? Because if you had a wire edge but chopped something hard, it would get flattened or knocked off and you wouldn't see it -- but cutting veggies it would fold over and still be visible. ??
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I did wonder if it was a wire edge, but I'm sure I'd still see some edge rolling after cutting up a chicken? It still slices paper after cutting up a chicken. I've even gone as far as cutting the edge against a stone to get rid of the edge, carefully sharpen it again, strop, and still get the same results. At this point I'm thinking it's my cutting board because the edge doesn't really come in contact with the cutting board much when taking apart a chicken but does make a lot of contact when cutting veggies
 
I tried cutting veggies on a wooden cutting board now and still got a bit of edge rolling. So being fed up, curiosity got the better of me and I just said "f*** it", clamped about one inch of the blade in my vise and decided to bend the blade to see if it snaps or bends. It snapped. Quite easily I should add. Got to about 30 degrees of bend before snapping. This indicates that the blade did in fact harden. Still doesn't answer my edge rolling issue but at least I know the blade hardened.
 
Your edge may be too thin, Resharpen the remainder at a higher angle and test it out.
 
If you have any pics, even post breakage, that might help. How did the grain look when you broke it?
 
i think it is still soft. most cannot rely on color, but you can rely on a magnet. the correct temp is one shade of red brighter than non magnetic. i think 01 requires a soak ?
 
Just a thought. Where did you get the O2? I had a similar problem when dealing with 80CrV2. It's the way the steel comes in. It needs to be normalized to even get it to harden. I think the big carbides will let it cut some harder stuff but it isn't hard enough to hold a fine edge. I'm not big on doing all the work to do all the work to make a knife and not have it turn out. I don't care much for forge heat treatment because I'm not good at it but if you want to do it I would recommend getting your steel from AKS. They are the only one I know that has all of their steel ready to heat treat. If you value your time making a knife is kinda expensive and it's worth sending it out for professional heat treatment. You are still making the knife.
 
Drew Riley said:
If you have any pics, even post breakage, that might help. How did the grain look when you broke it?
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I can't get a good pic with my phone, but the grain growth is a little bit coarse, which suggests I've overheated it I believe?
Storm W said:
Just a thought. Where did you get the O2? I had a similar problem when dealing with 80CrV2. It's the way the steel comes in. It needs to be normalized to even get it to harden. I think the big carbides will let it cut some harder stuff but it isn't hard enough to hold a fine edge. I'm not big on doing all the work to do all the work to make a knife and not have it turn out. I don't care much for forge heat treatment because I'm not good at it but if you want to do it I would recommend getting your steel from AKS. They are the only one I know that has all of their steel ready to heat treat. If you value your time making a knife is kinda expensive and it's worth sending it out for professional heat treatment. You are still making the knife.
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Got it from Bohler. They call it K460. They do provide heat treating services so in future I will be using them. After spending so much effort on making a knife, especially since I mostly use hand tools like a file for the grinds, to heat treat it myself with shady heat treatment methods is a waste of time. I was just curious as to why my edge was rolling on soft material even though it passed multiple edge tests. Your theory on the big carbides makes sense
 
emjay said:
I can't get a good pic with my phone, but the grain growth is a little bit coarse, which suggests I've overheated it I believe?

Got it from Bohler. They call it K460. They do provide heat treating services so in future I will be using them. After spending so much effort on making a knife, especially since I mostly use hand tools like a file for the grinds, to heat treat it myself with shady heat treatment methods is a waste of time. I was just curious as to why my edge was rolling on soft material even though it passed multiple edge tests. Your theory on the big carbides makes sense
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Some steel comes in a state called large spheroids. I'm not a expert and the best thing you can do is read Larrin Larrin 's knife steel nerds website or better yet get his book and it's a bargain. The way I understand it is that it is a lot easier to drill and machine in that state and especially with steel that is commonly used in industry it is desired. I used a small forge and followed the same direction that you did and most of the time it would get hard although it probably isn't the best. It did get sharp and overall I was happy then I came to the problem steel that is supposed to be a good beginner steel and had similar problems. When guys forge they know that they have to deal with it but when we do stock removal most of the time we don't have to but that can cause problems. It is a bit more complex steel than something like 1084 so there are a lot of things that could go wrong as well but it does sound a lot like the problems I had along the way. I scratched my head for a couple of months until someone mentioned that it's a issue with steel from that supplier. To be clear if that is the problem it's not a defect it's just how it was made. I bought a oven so I wouldn't have to guess but since I'm not trying to do it by eye there is no reason not to use a steel with more performance. When you go through through all the work to make a knife it's kinda nice to get the extra performance. Using a alloy steel or stainless can usually make things easier even. High alloy can be easier because it can be thinner at the edge when they harden it. If I remember right most places are ok with 0.010 at the edge and you can do a lot of your finish sanding before you send it in. That isn't as thin as a lot of us like to go in the kitchen but it isn't very thick as far as commercial knives go. If you want the edge finer you can just convex the edge in. That's not a bad way to go in the kitchen anyway. Hope things go well for your second one. Don't give up. Let us know if there is anything we can do to help earlier in the process. How are you going about it? A fileing jig? I had made some crappy ones when I was a teenager and then learned enough to think I needed tons of equipment and then waiting until I could afford it. That was a mistake. I think the time it takes to make one by hand might help a person take the time to plan and make a well made knife and perhaps do a bit better with design. The biggest mistake that I did and a lot of others do and did my best to toss together a bunch of stuff that I had wanted changed about knives that I had in the past and just had at it. For me at the time it wasn't the worst thing since I didn't have much time and was stressed out and just wanted to stand in front of the grinder. It didn't make the knives better but I learned a few things. The best thing I can recommend is to read through the "What's going on in your shop thread" and get some ideas about what you want to build unless you already have something in mind. You can carve a prototype out of wood and work out any problems before you start in on what you want. You will be surprised how well you can do. Custom heat treatment can hold up to a much thinner edge and and if you do a nice grind you can get way more performance than anything you can buy off the shelf. Good luck.
 
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