12c27mod vs. 12c27

[davek14]

What are the differences between 12c27mod and 12c27? I've looked up the compositions, but what are the differences?

Opinel uses the mod and is softer than, say, an EKA (which I think is 12c27).

Anyways, which is better?

 

[Shorttime]

It has more to do with the heat treat than the starting composition of the alloy.

12c27 modified has more chromium, relative to it's carbon content. If I remember right, this should result in higher hardness, and a finer grain structure, making the steel more resistant to chipping, and better able to tolerate lateral stress without cracking.

Folks on other forums sing the praises of 12c27, saying it's easy to work, easy to sharpen, and holds a good edge for a long time. If the modified version improves on these strengths, it ought to make an excellent blade.

The best way would be to get one of each and test them on the things you cut. Depending on what you do, and where you do it, there are many other factors that can influence your decision on blade steels.

 

[jimnolimit]

12C27 = 0.6% carbon and 13.5% chromium
12C27mod = 0.52% carbon and 14.5% chromium

12C27mod, because of it's lower carbon and higher chromium content will be more corrosion resistant and tougher.

12C27, because of it's higher carbon content, it will be a little more wear resistant and will be able to be taken to a higher hardness.

 

[photonjunkie]

Based on on the info on Sandvik's website, 12c27M is designed to be more corrosion resistant hence the higher chromium content as compared to the "standard" 12c27. It's carbon content is slightly lower though so its hardness is range is also lower as compared to 12c27 (thought there is a fair amount of overlap). Every company has their own target hardness though so it's difficult to compare knives from different manufacturers.
edit: Oops. Jimnolimit beat me to it.

 

[me2]

With respect to knives, 12C27M was intended for higher toughness and better corrosion resistance, while still having high strength. Think of it as the 5160 of stainless. The above posts have it right on. Were I to want a 10" chopper in stainless, this is what I'd use.

 

[davek14]

So, not a lot of difference is what I'm hearing. Once again, look to the manufacturer and his reputation for heat treat. Thus why we get on these boards and ask others what their experience may be.

From Ragweed forge...
Norwegians like the edges to be about 58. Swedes seem to like harder edges, with stainless blades hardened to 58, but carbon steel blades hardened to 60 or 62. It’s important to remember that an average steel with a good heat treat is much better than any steel with a poor heat treat. Many commercial makers will temper the blades on the soft side, if only because it’s easier on the production equipment. Heat treat is often given insufficient consideration. It’s difficult for the average user to know if the heat treat is properly without extensive testing of the blade. Here you almost have to go on faith, hopefully based on knowledge of the maker’s reputation. Some of the better suppliers will tell you the Rockwell rating of the blade, and this is a real help if the information is accurate.
*****
Anyways, my cheap self likes 12c27 from EKA and Frosts (in the Mora). It's a good, medium range stainless and I can get it somewhat near carbon steel in sharpness.

 

[me2]

Anyways, my cheap self likes 12c27 from EKA and Frosts (in the Mora). It's a good, medium range stainless and I can get it somewhat near carbon steel in sharpness.

12C27 remains one of my all time favorite steels. Few knives use it, and I'm not sure why. I have yet to try 13C26. I must say, with relation to ultimate sharpness, there is no difference between it and plain carbon steel. The knife world myth of stainless being difficult to sharpen and carbon steel getting sharper does not apply here (or anywhere else, since it's a myth). You may well have trouble sharpening it, but it doesn't have anything to do with the fact that its not a carbon steel.

 

[davek14]

Well, I mostly agree with you. I brought up 12c27 initially because it IS a steel I've found to be nearly as good as carbon in ease of sharpening and how sharp it will get. At least in the EKA knife I have, and in a Mora (although I don't love a Mora's grind).

Still, on your lower end stainless like 440a, or whatever Rough Rider uses, or a lot of your "no name" stainless steels out there you get the "myth". They take forever to sharpen and dull after one or two cuts. You sharpen and sharpen and the edge never gets scary sharp.

If you get at least a mid range stainless it's a lot better. I've gotten good results from AUS8.

Of course, all that has been said on heat treat applies. I've had other AUS8 that wasn't as good.

But, yeah, 12c27 can be a great steel.

It would be great if there was a chart with all the makers and their steels and everyone's experience with the heat treat. It would have to be updated frequently as makers move work to China or change processes. Oh well, I can dream.

12C27 remains one of my all time favorite steels. Few knives use it, and I'm not sure why. I have yet to try 13C26. I must say, with relation to ultimate sharpness, there is no difference between it and plain carbon steel. The knife world myth of stainless being difficult to sharpen and carbon steel getting sharper does not apply here (or anywhere else, since it's a myth). You may well have trouble sharpening it, but it doesn't have anything to do with the fact that its not a carbon steel.

 

[me2]

Those lower end (less expensive) steels also typically have lower end heat treatments. They tend to get very tenatious burrs that will drive even the most experienced sharpener crazy. You can modify your technique to remedy this but it takes some practice. 440A and similar alloys with a custom heat treatment will absolutely shock most people with their performance. Im harping on this a little bit because Ive seen the superior edge that 12c27 will take when heat treated properly. For the same effort, the sharpness was far above what I was used to getting from steels ranging from 440c to 1095. With some effort, the edges were equal, but it required some different procedures.

 

[davek14]

How do you modify your technique? With a secondary bevel? I'm not a great sharpener by any means. I usually use varying grades of emery cloth, coarse to fine.

Doesn't the fine or coarse carbides have something to do with this?

Those lower end (less expensive) steels also typically have lower end heat treatments. They tend to get very tenatious burrs that will drive even the most experienced sharpener crazy. You can modify your technique to remedy this but it takes some practice. 440A and similar alloys with a custom heat treatment will absolutely shock most people with their performance. Im harping on this a little bit because Ive seen the superior edge that 12c27 will take when heat treated properly. For the same effort, the sharpness was far above what I was used to getting from steels ranging from 440c to 1095. With some effort, the edges were equal, but it required some different procedures.

 

[me2]

How do you modify your technique? With a secondary bevel? I'm not a great sharpener by any means. I usually use varying grades of emery cloth, coarse to fine.

Doesn't the fine or coarse carbides have something to do with this?

For 12C27, the carbides can basically be ignored. That steel has a low carbide volume and the ones present are very small. The steel and recommended heat treatments were intended to produce this result.

I use a secondary bevel almost all the time now. I also include, when needed, a specific step for deburring the edge. Other changes I made are using a belt sander with a leather belt and compound for quick sharpening sessions, making sure my stones are clean and flat, and using very light pressure for the final honing stages. Changing abrasives helps in some cases as well.

 

[davek14]

I usually use about 12" pieces of 1.5" emery cloth double sided taped to pieces of metal bar stock. I know it's good to get a big flat surface to true up the edge. I work back and forth to reprofile at about 30 degree inclusive. When near done I'll go to fine grit emery cloth and work just one side till I get a burr along the whole edge, then the other till I get the same.

Then I work back and forth between sides at a greater angle lightly to fold the burr off. I finish by steeling.

For 12C27, the carbides can basically be ignored. That steel has a low carbide volume and the ones present are very small. The steel and recommended heat treatments were intended to produce this result.

I use a secondary bevel almost all the time now. I also include, when needed, a specific step for deburring the edge. Other changes I made are using a belt sander with a leather belt and compound for quick sharpening sessions, making sure my stones are clean and flat, and using very light pressure for the final honing stages. Changing abrasives helps in some cases as well.

 

[me2]

Any estimate of the emery cloth grit? I have never favored steels for final honing and there in lies the likely difference in our experiences. Are you using stropping or pushing strokes on the emery paper? For final pressure the weight of the knife is too much. It requires a feather light touch. I have to be sitting down and use both hands for the light touch needed. Also, if you're not, try using pushing strokes. The light passes dont come into play until after removing the burr. Before that it wont matter. Is your steel smooth or grooved?

 

[jimnolimit]

i own one honing steel, it's diamond coated and i only use it to maintain the edges of my kitchen knives that are hardened in the mid 50's (HRC).

 

[me2]

I really need to try one of those. I dont really consider them "steels" though, since they are covered with abrasive particles. I hear they work well and provide a nice aggressive edge for kitchen slicing. They should work fine for any western style kitchen knives, even the harder ones into the low 60s of hardness. I dont know about japanese styles though.

 

[davek14]

Hmm, 80 or 100 with a new blade to reprofile strokes are whatever, back and forth often.

Going to 250 or 320 (used 250 is like 320) with push strokes to finish.

Don't go near as light as you at the end, maybe during burr removal. If you go heavier at a greater angle during burr removal you are making a secondary angle (you are anyway, just a tiny one).

I use a smooth steel, often just a smooth piece of carbide. I don't ALWAYS do it, the goal is burr or feather edge removal more than aligning. Sometimes I'll strop on my arm or pants.

Any estimate of the emery cloth grit? I have never favored steels for final honing and there in lies the likely difference in our experiences. Are you using stropping or pushing strokes on the emery paper? For final pressure the weight of the knife is too much. It requires a feather light touch. I have to be sitting down and use both hands for the light touch needed. Also, if you're not, try using pushing strokes. The light passes dont come into play until after removing the burr. Before that it wont matter. Is your steel smooth or grooved?

 

[jimnolimit]

i sharpen only enough, just to the point that a burr will be made. i don't see the need to work up a burr just to knock it off, once both sides of the bevel meet ^, i move to a finer grit/strop.

p.s. i use canvas loaded with fine abrasives to strop.