Edge testing on 1084, L6, 52100 and D2 blades supplied by Ray Kirk

C

Cliff Stamp

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This is the first part of some testing done on four blades supplied by Ray Kirk. The geometry is identical (as close as you can get with hand work) but the steel types are different. The purpose of the work was to illustrate not only the difference in edge holding on an abrasive and difficult to cut material, but to also look at issues with sharpening and edge durability.

The blades were supplied to me with the steel type unknown, just marked A,B,C and D. At the start of each round of testing I had a friend tape over the markings and write 1,2,3,4 on them. Once the round of testing was completed I removed the tape and noted which one was A,B,C and D. This was done to insure that no bias would be introduced into later rounds by the results of the previous ones.

Here is the main body of the work :

http://www.physics.mun.ca/~sstamp/knives/ray_kirk_test_blades.html

It contains quite a lot of numerical data (surprise) and most of the tables are quite large. This took quite some time to do. At the end I was doing 2000 cuts per round into the mats used as blunting stock and the load required to drive the blades through the mats was quite high as the mats had a heavy tight carpet weave with a thick rubber underlay, the load on average was ~100 lbs towards the end. In total considering all the cuts done over the four rounds, ~500 000 lbs of force was exerted. This was not done in a day, nor even a week.

Here is the commentary which reveals which blades are which, one has a surprise feature, and gives my interpretation of the results, why the performance went as it did :

http://www.physics.mun.ca/~sstamp/knives/ray_kirk_test_blades.txt

I would like to thank Ray for loaning me these blades. This work was only the start of what I have planned for them. I have learned quite a lot for working with them, it confirmed a lot of what I believed to be true as well as explored new ground.

-Cliff
 
Excellent work, Cliff. Thanks for sharing.

And Ray, my good friend, thanks for making those knives available to Cliff for the testing.

The results are very interesting, especially since 52100 and D2 are two of my favorite blade steels.
 
Exhaustive, tenacious, imaginative and fair. A landmark comparative analysis of blade steels. Thank you, Cliff--and please keep on going!

-w
 
I would like to thank Cliff for taking the time and having the patience to perform all these tests. They are a great help to knife makers in developing the optimum blade for the job.
 
Very interesting Cliff, thanks for your work.

My only question(s) is about the L6 blade. Why the low hardness? It seems odd to me to compare the blades at 56-58 RC to a blade at 50 RC. I would like to have seen the L6 blade ata higher RC level. I hear L6 is a tough steel, so it seems odd to have a blade of L6 at such a low hardness. I welcome comments on this.

Thanks for the charts. It is easy to compare things that way and get a "feel" for the performance of different blades.
 
Crayola,
The L6, as used, was an old saw mill saw blade. I didn't have it tested for mill specs but checked to see if it would harden by heating and quenching. The 3 carbon steel blades were hardened by using clay to cover the back and tang. The edges were then brought up to critical and quenched. A friend of mine hardened the D2. All the blades were put into the oven at 400 deg. for 2 hours to temper them. The blades were then tested for hardness with a machine. A second temper of 450 deg. was to be done after all the cutting tests and then tested for hardness again. This would show how much 50 deg. in the temper cycle would affect the performance of the steels.
The only reason that I can give for the L6 is that it would require a longer soak time at critical to give a higher Rc in the beginning. A file did slide on all the blades the same. The L6 was checked 3 times each in two different spots on the blade to make sure it wasn't operator error.
When the blades are returned or after testing, I will try to have the Rc run on them again and an anylasis done on the L6 to make sure that it falls within the requirements of L6.
 
live and LEARN. I just hope I live long enough!!!!!!!;) Thank you Cliff, your knowledge and your willingness to share makes me the BETTER person each day as I grow knife-savy. Thanks so much......wolf
 
Great work. But I wonder how influential the forging/hardening/tempering process as done by different smiths is. I suspect a Fowler or Hayes 52100 or a Howard Clark L6 might perform differently. If so, how much differently?

Thanks, Cliff.
 
Interesting work Cliff. Thank you for taking the time to do it all. I was particularly interested in the nature of the edge loss (wear vs. deflection). Are you planning on doing destructive testing on these blades to see which is most flexible, most resistant to breaking, etc?
 
Originally posted by HJK
Great work. But I wonder how influential the forging/hardening/tempering process as done by different smiths is. I suspect a Fowler or Hayes 52100 or a Howard Clark L6 might perform differently. If so, how much differently?
Click to expand...

HJK,

I'm an admirer of the work of all three of those makers and have (had) blades by two of the three. I know that you certainly weren't implying any different, but just for the record I'd like to say that Ray's knives are up there with the best in terms of heat treatment and creating a sharp, refined edge. Ray is a true student of steel and its characteristics and hasn't won a couple of recent ABS cutting contests for nothing (though he'd be too modest to tout his successes himself).

Over the past few years I can't tell you how many phone calls and email messages back and forth Ray and I have shared with him explaining various stages and pros/cons of different methods of heat treating, quenching and tempering.

Still, it would be interesting to see how the results varied when other factors in the mix were changed up, but I imagine that could go on ad infinitum.
 
Blues, you are absolutely right and frankly, I'm ashamed of myself for leaving the impression that I thought Mr. Kirk's work may be in some way inferior to those other great Smiths. I apologize, because that was not my intention. Although I haven't had the honour of using or owning one of Ray's blades, I have heard that they are superb and I have no doubt that this is true.
What I meant, and incompetently failed to express, was that every blade that goes through the forging, tempering, and hardening process requires choices and tradeoffs in hardness, toughness, edge retention etc. Cliff, Ray and many, many others here know this much better than I. I'm not sure how this was taken into account in the making or testing of the blades.
My point, such as it was meant to be, is that different blades made by different smiths may have significantly different performance relative to other steels and even the same steel because of the choices and techniques used. And different steels may respond differently, or in different degrees, to the same techniques used with other steels. I don't know if the 52100 here was optimised for edge retention or impact resistance or if it was tweaked differently than the D2 for those characteristics. I think some smiths tend to favour different steels and optimise them for different characteristics. It's a very individual think that may yield different test results. Anyway, that was the question.
Anyway, before my clumsy fingers get me into even more trouble, I'll leave it to you who have more expertise to carry on. My apologies again. Thanks, Blues. Quite right.
 
HJK,

We've been friends long enough on this board that I knew exactly that that was what you meant and I just wanted to make sure that anyone less familiar with the parties involved didn't get the wrong impression. I'm glad you didn't think I overstepped. :)

By the way, I think one of Ray's knives would be just the thing for one of those great outings you always seem to have planned. ;)

This thread has great potential to educate many of us as to the various properties of our favorite steels.

Thanks again to Cliff and Ray for making it possible.
 
Ray, thanks for your reply. Now I am really curious how an L6 blade with a higher RC value would have ranked!
 
Crayola :

Thanks for the charts. It is easy to compare things that way and get a "feel" for the performance of different blades.
Click to expand...

Excellent, that was one of my concerns.

Now I am really curious how an L6 blade with a higher RC value would have ranked!
Click to expand...

At a similar RC (56/57) It would have been between the 1084 and 52100 blade in edge retention, below the 52100, but closer to it than the 1084. The performance would have been the opposite in regards to responce to sharpening.

Burke :

Are you planning on doing destructive testing on these blades to see which is most flexible, most resistant to breaking, etc?
Click to expand...

Yes, other tests will be performed.

HJK :

My point, such as it was meant to be, is that different blades made by different smiths may have significantly different performance relative to other steels and even the same steel because of the choices and techniques used.
Click to expand...

Yes, and where the steel is bought can also be a factor. Now does the 52100 vs D2 (for example) in the above cover every 52100 vs D2 blade out there? No it does not. For example if the D2 blade was tempered to 54-55 RC it would suffer edge rolling before the 52100 one at 57 RC (similar if the 52100 blade was brought up to ~60 RC). The D2 blade would still resist wear better due to the much higher percentage of Cr carbides, but the higher edge distortion due to lower RC (and therefore strength) would not allow this to come into play as the carbides would not cut along a coherent path. This is why the L6 blade fell so far behind the 1084 one, the carbides can't help if the edge gets too distorted / compacted.

What you should *not* do is use the above results to make large sweeping generalizations on steels, as the performance of a knife at a given geometry depends on the quality of the steel and the quality of the heat treatment, both as noted will vary from blade to blade depending on where the steel was bought and the skill and knowledge of the maker who did the heat treatment. What the above is intended to offer is to clarify how aspects of steel such as RC hardness and carbide composition effect edge retention and sharpenability (other aspects will come later). Ray of course, since he did the heat treatment can make much more specific conclusions.

Variations in steel is one of the things I have planned to explore. I have a 52100 blade from Ed Caffery, forged, single quench, multiple temper 57 - 59, no cryo. I have also ordered a forged, 24 hour multiple quench, multiple temper, no cryo blade from Bill Burke in the same edge profile and blade size. One I get them compared I plan on discussing the results with Phil Wilson and seeing if he can make a 52100 blade, stock removal, single quench, deep cryo, and multiple temper to explore pretty much the opposite perspective. Phil's blade will not of course have the extreme flexibility of the other two blades given it would all be at full hardness, ~ 60 RC. Ray's 52100 blade might also be used depending on how much influence I think the geometry will make and the time schedule.

Thanks all, I have some bone cutting work with these blades that will be posted up tomorrow.

-Cliff
 
The following bone cutting was done awhile ago, during the 52100 MEUK review actually. At that time I still didn't know which blade was which steel. Anyway, the work :

Each blade was used to section six chicken wings for dinner. A cut was made to remove the tip and one to separate the wing, twelve cuts in all with each knife. Five cuts were made clean through the joint, minimal bone contact, minimal force. Five cuts were made in a sloppy manner through the joint, ~50 lbs of force. Two cuts were made behind the joint, right through the bone, ~100 lbs of force required.

Blade A (1084 / 56 RC) :

-no visible damage
-thumbnail check was smooth
-light reflected along center of belly a few mm

Blade B (L6 / 50RC) :

-no visible damage
-thumbnail catches
-only about 2 cm of clear edge under light, the rest reflects strongly

Blade C (D2 / 57 RC):

-no damage detectable under any of the above means

Blade D (52100 / 57 RC):

-only one small bit of reflected light, smaller than A

This was when I got seriously confused. I could understand the edge retention work on the mats, however when blade B got so damaged it threw me completely as I had assumed it was 1084 (with A being L6 and C and D being D2 and 52100 respectively). This was where Ray had interjected a surprise, I had assumed all the blades were of similar RC - they were not.

The explanation :

C (D2 / 57 RC) :

-The combination of high hardness and large percentage of Cr carbides allowed the edge to resist compaction completely.

D (52100 / 57 RC) :

-Due to the smaller amount of Cr carbides it suffers just a little more impaction than the D2 blade at the same hardness.

A (1084 / 56 RC) :

-With a point disadvantage in RC and a total lack of alloy carbides, the edge is impacted significantly more than the D2 blade

B (L6 / 50 RC) :

-With a seven point disadvantage in RC the edge sees significant compaction, the lower percentage of alloy carbides doesn't help either, but the RC difference is the largest factor.

To show that this was distortion and not wear, I used a lightly grooved steel on the L6 blade with two dozen strokes per side. I followed this up with the Razor's-Edge smooth steel, again two dozen strokes per side. Only size small (0.5 mm long) distortions remain. The blade was now just under hair scraping sharp.

So in short, what the above shows is that a harder blade will resist compaction better, and at the same hardness, a blade that is made from a steel with a higher alloy content will fare better. The rank goes; D2 then 52100 (just a little behind C), 1084 (a larger drop than D2 -> 52100), and L6 (a much bigger drop than 52100->1084). So, qualitative :

D2 at 57 RC = 10
52100 at 57 RC = 9
1084 at 57 RC = 7.5
L6 at 57 RC = 1

Note this is not chopping, but strong controlled press cuts. These are very different tasks for a blade. The best at one is likely not to be at the other. Chopping demands a high impact resistance, strong press cuts demand a high compaction resistance, these are pretty much effected by the opposite way in regards to materials structure. More on that to come.

Some specifications :

The edge angles were checked in multiple places along the blades with a set of calipers. The knives made from 1084, L6, and 52100 were found to have the edges ground to 13-14 degrees. The D2 blade had an edge angle *just* under, 11-12 degrees. Thus there was about a one degree difference in the edge of one blade, just at the level that I could detect.

The cutting ability of the blades was tested on wood by whittling points on scrap. When all the blades were sharp I could detect no difference in the push cutting ability on the wood. The knives took between 8-10 cuts depending on the nature of the wood.

-Cliff
 
Your reveiw bears out the feedback I've been getting from customers that have been purchasing the new Marbles knives I sell in my shop. A very picky customer came in the shop with high praise for his new Marble. He harvested a medium sized bull moose while hunting alone. He used the Marble exclusively for skinning, gutting, and boning out the animal at the kill site. He brought the knife into the shop with the great news of the knifes' edge holding ability. He never had to sharpen the knife through the whole process. I checked the knife under a magnifier and it still looked new. I then tried to shave the hair on my arm and was suprised to find it still would shave. I could tell it wasn't like a new Marbles shaving but I was impressed. With a few strokes on my sharp maker it was like a factory edge again. 52100 is a top of the line blade steel in my book.:D
 
Thank you for a very informative study, Cliff. I do have a question, however. How do you suppose the D2 sample would vary if the RC was 60-61 instead of 57RC?
Regards,
Barry H
 
Text taken from the above study:

FINAL ROUND :

Thread : Not done, it takes a lot longer to do than the poly and I got lazy.

Heh heh heh. So we can assume that arm strength and endurance are essentially the same for all 4 blades, no? No slave to science are you, Mr. Stamp. ;)

I remember the threads then, and recall that it stuck a couple of questions in my mind at the time. Those questions have been sufficiently rooted out and answered here, I must say. With a vengeance. Thank you Cliff, for your phenomenal efforts in this endeavor. I've learned a great deal from it. And just as many thanks to Ray Kirk. Men of your calibre make this place well worth the multitude of clicks that it takes to get here. :)
 
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