CTS-20CP Performance

[phillipsted]

I've been carrying my grey Para2 sprint a lot lately and giving it some solid around the house/yard workouts.

I was excited when this came out because of Ankerton's edge retention rating for this steel (Ranking-of-Steels-in-Categories-based-on-Edge-Retention). He puts it in category one with S90V and M390. However, over the past month, I've lowered my expectations for the performance of this steel - and I wonder if my experience is typical of every one else.

I got a good bevel on the edge of my Para2 at about 32° - and I don't normally run a microbevel. I proceeded to use the knife for normal around the house chores - opening letters and packages, trimming cardboard, light carving on wood, etc. The toughest challenge I gave it was making about a 12 foot cut across a carpet end roll.

Well, today, after about three weeks of "normal" usage, my son borrows my Para to cut out a coupon out of a paper flyer. The blade wasn't sharp enough to cut the thick paper without tearing it. I looked at the bevel with a 10x loupe, and some parts still had a decent edge, but in other places the edge was deformed or chipped.

Now you guys know me - I wasn't banging this edge into rock or steel posts. I was a bit shocked that the edge didn't hold up as well as I anticipated. I give S30v knives this type of treatment and often get better edge retention. Anyway, I sharpened this thing up tonight - and with minimal effort, it was scary, hair-popping sharp once again.

I was just curious, since this is a relatively new steel for us Spyderholics, has anyone else had experience with keeping an edge on 20CP?

TedP

[phaust]

There is a lot of talk of carbides being ripped out of high-carbide steels at lower angles. 32 might be a little low. Here is a thread with some good info http://www.bladeforums.com/forums/showt ... Resistance. Also, there's a picture in there of s90v after use, post 12; is that what yours looks like?

[hawaiihunter]

still looking for one of dem grey ones, i almost got one too.

[Cliff Stamp]

I give S30v knives this type of treatment and often get better edge retention.

If you took a half a dozen S30V (S35VN, etc.) blades and a half a dozen S90V (CTS-20CP, etc.) blades and did equal work with them then *on average* *through repeated runs* you would expect that the latter would hold a low sharpness for longer than the former, the difference only gets significant at very low levels of sharpness.

However picking one blade from each group and doing a random series of work with it, the performance could easily reverse. There is a lot of variation in steels due to composition, rolling, HT, sharpening, micro-composition at the edge, then there are all the factors which influence edge retention in use (materials cut, speed / force of cut, environment, etc.).

In short, there is a lot of variation, one run does not a conclusion make. If you experienced the same thing a few times and on average it was performing less than your S30V blades at holding a low sharpness then you could likely be safe in concluding that there is something off, the most likely factor is retained austenite if it is rolling and chipping.

[chuck_roxas45]

My experience with 20CP has been that it quickly went to low sharpness(difficulty in slicing paper) especially with cutting dirty cardboard. However, that low sharpness would hold for quite a bit longer than s30v would hold the same "level" of low sharpness. What I mean is that my 20CP para would still be able to cut cardboard without tearing it, after my s30v para would need unpleasant amounts of strength to make rough tearing cuts.

[Evil D]

My only issue is that it seemed to chip pretty easily at 30 inclusive, but a micro bevel took care of that.

[phillipsted]

Good point, Evil. I am going to put a microbevel on it today at about 40° and see if this helps out.

Oddly enough, this blade came from the factory with a primary bevel just under 30°. That may have been part of the issue here...

TedP

[bh49]

If you took a half a dozen S30V (S35VN, etc.) blades and a half a dozen S90V (CTS-20CP, etc.) blades and did equal work with them then *on average* *through repeated runs* you would expect that the latter would hold a low sharpness for longer than the former, the difference only gets significant at very low levels of sharpness.
However picking one blade from each group and doing a random series of work with it, the performance could easily reverse. There is a lot of variation in steels due to composition, rolling, HT, sharpening, micro-composition at the edge, then there are all the factors which influence edge retention in use (materials cut, speed / force of cut, environment, etc.).

In short, there is a lot of variation, one run does not a conclusion make. If you experienced the same thing a few times and on average it was performing less than your S30V blades at holding a low sharpness then you could likely be safe in concluding that there is something off, the most likely factor is retained austenite if it is rolling and chipping.

+1
Absolutely agree with Cliff that one sample is not sufficient to represent entire population. I understand limitations of knife enthusiasts doing testing, when they test one knife. But in this case, the test is not steel testing. This is testing of the one particular knife. Confidence level that steel will perform the same way like this knife is very low.
IMHO Ankerson's testing is level up to compare with most, what I saw on BF: he testing two knives and explains really well methods, accuracy and so on. Unfortunately many people do not read details or just forget them.
Statistically, if you want to have confidence level around 90% that entire lot will act like a sample, you need to have at least 30 pieces for lot over 100. Of cause if we are talking about blades, depending how accurate you want to be, different H/T batches need to be tested separate, for better accuracy different heats need to be tested separate as well. Probably only steel producers can afford such testing.

[Ankerson]

20CP is finer grained than S90V so it will tend to like a slightly finer edge from what I have seen.

Some of the problems could be from just working with the original edge instead of removing enough metal for a fresh bevel.

[Zenith]

There is a lot of talk of carbides being ripped out of high-carbide steels at lower angles. 32 might be a little low. Here is a thread with some good info http://www.bladeforums.com/forums/showt ... Resistance. Also, there's a picture in there of s90v after use, post 12; is that what yours looks like?

Carbide tear out does happen and it has been discussed well, however, IMO the particle/powdered steels due to their equal distribution minimise this effect. Truth be told. I am surprised there has not been MUCH more complaints about M390 or other high vanadium (a big carbide former) steels chipping out with some of the really low angles I have seen people do with it.

To my knowledge, speaking with a metallurgist the ideal amount of Vanadium to minimise gran growth is 0.2 percent. The demand for high Vanadium steels for knives seems to be the market created by knife nuts.

Either way. Push a knives edge as low as you can go until you experience extreme failure due to chipping or rolling and then increase it slightly. The only edge I had that really failed on me was a zero ground Opinel nr 8. So that was THIN! I have pushed M4 to 12-14 degrees per side at the edge with no failure in my uses (YMMV).

One of the biggest things that people forget is that with a new knife one sometimes need to remove up to the first 1mm of steel at the edge. There can be some damage to the heat treat due to sharpening process and heat building up. (Ankerson mentioned this in his post above about a fresh bevel)

[phillipsted]

+1
Absolutely agree with Cliff that one sample is not sufficient to represent entire population. I understand limitations of knife enthusiasts doing testing, when they test one knife. But in this case, the test is not steel testing. This is testing of the one particular knife. Confidence level that steel will perform the same way like this knife is very low.
IMHO Ankerson's testing is level up to compare with most, what I saw on BF: he testing two knives and explains really well methods, accuracy and so on. Unfortunately many people do not read details or just forget them.
Statistically, if you want to have confidence level around 90% that entire lot will act like a sample, you need to have at least 30 pieces for lot over 100. Of cause if we are talking about blades, depending how accurate you want to be, different H/T batches need to be tested separate, for better accuracy different heats need to be tested separate as well. Probably only steel producers can afford such testing.

BH and Cliff - I understand what you are saying here - I'm an engineer by trade. The problem is that I only have 2 CTS-20CP blades - so the extent of my experience with this new steel is limited. And I think this goes for almost everyone else - none of us have a statistically-significant sampling of the 800-odd knives in that sprint run.

I'm not trying to condemn 20CP or call into question Jim's testing process or extremely valuable results. Quite the contrary. What I'm saying is this: I've got two knives in this new steel, and neither of them performed up to my (probably inflated) expectations. This just means that I'm still learning about what makes this steel tick. Have I found the "sweet spot" for it yet? Nope.

TedP

[Cliff Stamp]

The problem is that I only have 2 CTS-20CP blades - so the extent of my experience with this new steel is limited.

It has to be kept in mind what we are discussing here of course which is user feedback, not a paid for research opinion of which that would be irresponsible behavior. When I first started using S30V my experiences were pretty low, I had blades which were so brittle they would not sharpen, edges which were so weak they rolled easily - and after awhile I had enough blades to see some very nice ones as well. Knowing that variance in steels is to be high I simply withheld opinion on the potential of the steel until I had seen enough to make some kind of estimate. It still is curious to me why S30V had the high variance it did.

All you can do is work with the knives you have realize that the performance of a steel is expected to vary a lot and that you may be on the short end of the stick. The only things that I would suggest before you make a conclusion on the knives are :

1) Sharpen it a few times and I don't mean "touchups" I mean actual sharpen it and start by removing all weakened metal. This will ensure you are not simply seen damaged metal at the edge which is common.

2) Rotate in another blade and give it a few cycles to see if a consistent pattern results. The performance difference of these steels is not that large that variance in work itself could not exceed the behavior of the steels. Even comparing something like AUS-6A vs S30V, two difference types of cardboard boxes for example could make S30V the loser in such a comparison if it gets the highly abrasive cardboard.

If you have done this, sharpened, carried a few times, and on average S30V is actually showing a higher resistance to wear than CTS-20CP (or higher deformation resistance) then it would be the time to write up a short email, summarize the results fire it off to the manufacturer as that really can not be the expected performance.

[Mjolnir74]

I had a gray para. I carried it daily for about 8 months. I used it for everything from cleaning fish to cutting 2"thick limbs off of an oak tree. I had a 30 degree inclusive bevel on it. The edge held good with maintanence being loaded strop every few weeks. I think I really only sharpened it 2-3 times on my apex. Overall I thought the steel was much better than S30v.

[eloreno]

I have been very pleased with the performance of 20CP. I would recommend, as others have above, making sure you've got fresh steel at the edge.
I had mine reground very thin, with great results. I am sure when it was reground, there was fresh steel at the edge.
In my opinion, 20CP definitely delivers noticeably better performance than S30V.

[phillipsted]

Cliff - I started this thread intending to solicit others' opinions/experience with CTS-20CP. You've provided a lot of general feedback that could apply to any steel - if you've used 20CP, please let us know your thoughts. :cool:

TedP

[angusW]

I just noticed yesterday that my Grey Para 2 is somewhat dull and this is after I cut a metal can with about 5 or 6 full cuts and then sharpened it to 30° until it could push through phone book paper. There was chipping after cutting the can but I think that was due to some twisting on my part but I did have to remove quite a bit of material to get a new edge. That was back in mid Feb. and I haven't sharpened it since. Only stropped it a couple of times. I've let it go a bit but I would definitely put it's performance above s30v.

[shqxk]

I have Blue Para2, Grey Para2, Orange Para2 and plain s30v Para2. All of them had been used for decent amount and I really cant noticed any superior edge retention between them. M390 and CTS20CP both got dulled after been cut on large amount of papers, same as s30v. IMO what people called 'super steel' is overrated since it not that better than ordinary steel like s30v.

[chuck_roxas45]

I have Blue Para2, Grey Para2, Orange Para2 and plain s30v Para2. All of them had been used for decent amount and I really cant noticed any superior edge retention between them. M390 and CTS20CP both got dulled after been cut on large amount of papers, same as s30v. IMO what people called 'super steel' is overrated since it not that better than ordinary steel like s30v.

What bevel angles? What edge finish? What material did you cut?

[Evil D]

I have Blue Para2, Grey Para2, Orange Para2 and plain s30v Para2. All of them had been used for decent amount and I really cant noticed any superior edge retention between them. M390 and CTS20CP both got dulled after been cut on large amount of papers, same as s30v. IMO what people called 'super steel' is overrated since it not that better than ordinary steel like s30v.

I've never seen a steel that won't lose a hair popping edge within the first few cuts into something. What these steels are good for is varying degrees of edge retention and/or toughness over S30V. You have to push them and cut a lot to see their benefits.

[chuck_roxas45]

I've never seen a steel that won't lose a hair popping edge within the first few cuts into something. What these steels are good for is varying degrees of edge retention and/or toughness over S30V. You have to push them and cut a lot to see their benefits.

Yep, Mr. EvilD is correct. If you don't really cut lots of stuff, you won't really be exploiting the capabilities of "supersteels".