What I Have Been Up To Lately

[Marko Tsourkan]

Yesterday, JohnyChance and Uptothehilt came over to help with a rope cutting test and to learn about making sayas. I went over the basics and did a quick carving demonstration for one of JC knives. We didn't go past that, as I glue sayas overnight, so the next week we pick up where we left off this week- shape, sand and oil-finish it.

For rope cutting test, we selected several knives with comparable thickness above the edge. I made a makeshift cutting station - an end-grain block attached to a digital scale with an external reader. For counting cuts, we used a mechanical click counter. We used 1/2" sisal rope.

JC sharpened all knives to same lever of sharpness, using same stones and strop. We exposed about 2.75" of edge, to speed up dulling.

The test asked for a pull cut, however, we did it with push cut, as it seemed a little more natural when cutting rope. At some point later, we will redo it with a pull cut and compare the results.

As this was an experiment (with not very high expectations), I am not going to post results, as we need to improve cutting technique (cutting 1/2" sisal rope is nothing like food) before we can use numbers in any meaningful ways, but I think we got a good feel for it.

It was pretty obvious that choice of steel and heat treatment had a direct effect on rate of dulling. However, some steels continue cutting even after they were dull to the touch, while others quit. Once we get better at testing, I will elaborate about this.

Overall, it was an interesting experiment and I want to thank both members for coming over and helping out. I hope we can do this more frequently.

M

[DeepCSweede]

Can't wait to hear more Marko, keep us posted. thanks for sharing.

[JohnnyChance]

Cutting sisal rope is definitely not as fun or as fast as cutting up food.

[Johnny.B.Good]

I enjoy reading all of this and know you have good reasons for everything you do, but what exactly are you hoping to learn through the rope cutting tests? Durability of the various steels and heat treatments?

[JohnnyChance]

Edge retention mostly but also stability. We tested other steels because we are curious, but the real benefit for Marko is testing different version of his heat treat for a given steel. Let's say theoretical HT #1 is easier to sharpen than HT #2. If they both cut the same amount of rope, why bother with #2? Or maybe #2 cuts twice as much as #1, is the extra edge retention worth the trade off of being more difficult to sharpen? Maybe #2 cuts 25% better than #1, but it also experiences some chipping. We can test these side by side in under an hour, cutting the exact same thing in the exact same way.

[Johnny.B.Good]

Edge retention mostly but also stability. We tested other steels because we are curious, but the real benefit for Marko is testing different version of his heat treat for a given steel. Let's say theoretical HT #1 is easier to sharpen than HT #2. If they both cut the same amount of rope, why bother with #2? Or maybe #2 cuts twice as much as #1, does the the extra edge retention worth the trade off of being more difficult to sharpen? Maybe #2 cuts 25% better than #1, but it also experiences some chipping. We can test these side by side in under an hour, cutting the exact same thing in the exact same way.

Interesting; thanks for the explanation.

[Marko Tsourkan]

Thanks, John for chiming in.

yes, these tests are useful to assess heat treatment, particularly when one is aiming for a certain outcome like wear resistance, sharpness or edge stability. It should also be possible to compare different steels' performance side-by-side, provided that geometry on knives is similar.

For now, we concluded that the latest HT for 52100 has better wear resistance than my previous, without sacrificing much of an ease of sharpening, so naturally, I will adopt it for all of my 52100 knives going onward.

There is one steel that we tried (for now I won't name it, plus I am not 100% sure what it is) that showed some impressive edge retention. I think I will give this steel (or steel I think it is) a close look in the coming months.

Then there is a powder stainless steel that I would like to evaluate and to see how it stocks up to 52100.

An ultimate test would be putting a knife into hands of somebody in a pro kitchen and ask them to use it without resharpening for as long as they can, and then use a feedback information to assess heat treatment, geometry, etc.

Rope cutting test, however incomplete, offers a snapshot about knife's performance, and though it might not be as accurate as when cutting an actual food, it will point you in a right direction, I think. Many makers have done it on their road to making performance knives.

Hope this explains it.

M

[Crothcipt]

I was wondering about the whole knife test, and how it applies to food. (I mean the masters test) Would cutting a piece of food at the end be beneficial in the test? Would it also help show how the ht is related?

[Marko Tsourkan]

I spoke to a forum member today and he suggested to try to cut a tomato after every 100 rope cuts. I don't know if it will work or not, as sisal might kill the razor-edge pretty quickly, but I will try it. Always open to suggestions, so don't be shy to chime in.

M

[Crothcipt]

I was thinking more like celery. I think the tomato would be to picky. Celery would show on the threads how the cut is affecting the food.