Cardbard cutting with CRK&T M16-14 and M16-14Z

[Cliff Stamp]

I think these knives are AUS-8A at 56/58 HRC (M16-14) and AUS-4A at 55/57 HRC (M16-14Z) respectively. However there are a bajillion types of M16's and I didn't find the exact specifications on the M16-14Z, I am fairly confident on the other aluminum one though, if anyone has a webpage with an exact reference to the steels in these two knives it would be appreciated :

http://i7.photobucket.com/albums/y269/CliffStamp/crkt/m16 zytel/m16.jpg

I intended this to be a comparison of these two to the Point Guard in AISI-420 and a VG-10 blade as a reference, likely adding the South Fork as a high end benchmark as I had a over 160 m of cardboard, and considering how fast the Point Guard went blunt in the last comparison I figured I had lots of room to spare. Ref :

http://www.bladeforums.com/forums/showthread.php?t=397768

I left the blades with a really rough finish, the coarse side of a coarse/fine hardware stone, which feels like the 90 grit of side of others I have used. The edges were used fresh from the stone after wiping them on paper towel to remove the abrasive, no stropping on leather/paper.

The knives would shave with a little draw (not catch hair above the skin), push newsprint at about a half an inch from the point it was pinched between thumb and index finger, easily slice paper towel, etc. . After each round the edge was freshly sharpened and initially cutting into the side of the stone 2-4 passes to remove weakened steel and insure that only quality steel formed the edge with each sharpening.

I started slicing 1/8" ridged cardboard with a steady speed of 1-2 seconds per foot of cardboard using 3 cm of edge on the plain edge part to do the cutting. I measured the sharpness at basically every 2^n cuts. The blades keep cutting ver well, also checked on newsprint and even kept shaving. At 40 meters and the blades still shave at the end but need enough force and a draw so that the skin is irritated, and they won't push cut newsprint at a 90, but can do it roughly at an angle, and still slice it easily.

I check the edge under magnification and there is very little deformation, the edge was kept at the stock profile which is chisel ground at 15 degrees included, so basically 7/8 degrees per side on a v-ground bevel. No specific micro-bevel applied except what was applied to remove the burr which was a few passes on the ground side, the back was always lapped straight to the stone. I did four runs with each blade and the results were very consistent. As a graph :

http://i7.photobucket.com/albums/y269/CliffStamp/crkt/m16 zytel/m16_card_light.png

The curves are splines (gnuplot - freeware) and used just to check trends when a n exact model isn't known. Note the extremely low rate of blunting aside from the first few points, consider that in order for the knife to actually start to rip the cardboard this has to reach 3.4-4.5 cm and it looks like the graph is again starting to take that plateau in the far right section, investigating the point of actual failure to cut would have required a truely massive amount of cardboard.

I have seen this extreme responce on hemp rope but this is the first time I have tried this in detail on cardboard. The combination of really coarse edges at acute profiles just eats a monsterous amount of cardboard to no effect. I am rather curious what would happen if I did the same thing with the South Fork, does it retain the large advantage it had at the fine finish, or is the really coarse finish an equalizer?

In any case, even if you are not interested in the curvature of the graph (which I am as it looks to now have possibly three rather distinct regions) and the numbers, just consider the amount of cardboard that can be cut with these "low end" steels with consideration given to edge angle and sharpness. That is literally hundreds of cuts through feet of cardboard and the knives still have lots of fine cutting ability.

I considered that maybe that cardboard wasn't overly abrasive as there was no external benchmark so I started another trial on 1/4" cardboard which is very hard to cut, the M16-14's are ripping through it, though I was able to cut enough to remove the shaving ability and prevent them from push cutting newsprint, who would have figured that would be difficult.

But forget about losing newsprint slicing ability or even coming close to actually ripping the cardboard. I should have that done in about a week and will hopefully have enough to benchmark it against at least VG-10 or S30V to verify the nature of the cardboard, but I really don't think that is an issue based on what I have cut in the past as I have never seen the level of variance needed to explain the above.

Getting them sharp takes a little work, specifically it takes about 25-35 passes on the stone to set the primary edge and then about the same to lap the back and produce a visible burr (this is really large as in you can see it by eye folded over). This is then cut off with a few high angle passes on the front and lapped on the back. The stone it pretty crappy though and doesn't bite in well and it is difficult to get even pressure as the surface is also really uneven, so the above is also a low end estimate as the initial edge quality could be better.

-Cliff

 

[DGG]

Thanks for posting that review. Often we think we must have the latest wiz-bang diamond impregnated steel in order to have a cutter. I have wondered about those M-16's. There are numerous models and it gets confusing. I like the style.

I recently found a very similar knife that I'd like you to put through this exact same test. It is a Gerber Air Ranger one had an AUS-8a blade and the other some 440 something or other. I found them at a price that caused me to buy a bunch as gifts. PM me if you want one to test.

http://www.eknifeworks.com/webapp/e...earchText=Ranger&Mode=Text&range=11&SKU=G5860

http://www.eknifeworks.com/webapp/e...earchText=Ranger&Mode=Text&range=11&SKU=G5920

I gave one a couple stroke on a hone and it is going strong after about a month of shop cutting.

Have you ever tested a teflon coated blade? I wonder if it makes any difference in the ease of cutting or if it is just a marketing gimmick.

http://www.eknifeworks.com/webapp/eCommerce/product.jsp?Mode=Brand&Brand=49&SKU=G5849

 

[kel_aa]

These appear to be ground higher up than the spear point ones.

Are you sure about the 15 degrees included? That seems awefully aggressive for a factory edge.

The graph says there is no difference in performance between Aus 8 and Aus 4 in this case? Can you notice any different properties in the steels? Is it not possible they are both Aus 8?

 

[Cliff Stamp]

Are you sure about the 15 degrees included?

It seemed low to me so I measured it at four places along the edge, on both knives, it is fairly consistent, the profile is a little more acute than stock, but even then it was under 20 included. Most knives which are chisel ground have the primary straight edge and the serrations at two radically different angles, this one doesn't, in addition the hollow grind on the back actually goes into the primary edge on the front and thus hollows the edge out. The edge itself is basically flat on one side and hollow/flat on the other like a japanese chisel but to a greater degree. I confirmed the really acute profile by some hardwood whittling and even with the huge leverage disadvantage of having to cut so far out infront of the handle they still performed exceptionally well. I'll have numbers on them in a week or so, right now the review on the website has a few typo's including the information on the edge profile which says 20 degrees per side for some reason.

The graph says there is no difference in performance between Aus 8 and Aus 4 in this case?

Pretty much yes, there is some difference in the intitial responce but it isn't statistically significant and if you go out to where they have both made over a hundred slices there is no difference. I could not tell them apart on the cardboard either, aside from the Zytel one being more comfortable in hand.

Can you notice any different properties in the steels? Is it not possible they are both Aus 8?

The Zytel one seems easier to machine and in general I have more problems getting a crisp edge but the difference isn't very large and could just be variance from one piece to the next. I expected that there would be more of a difference in AUS 4/8 but it may be due to the heat treating of CRK&T which leaves both at near the same hardness. It also may be that similar to the above graph ranking S30V, the knives only really pull apart strongly in the region where they plateau. However it looks like at this grit finish it will take a mountain of cardboard to separate them. I'll try the same finish on used carpet later on and see if that makes more of a difference plus repeat this with the fine finish on the other side of the stone. I dropped CRK&T an email about the steel, no responce yet.

Often we think we must have the latest wiz-bang diamond impregnated steel in order to have a cutter.

Mike Swaim did a lot of working showing how cutting ability and edge retention were influenced by geometry and finish very strongly, Joe Talmadge did the same and showed how it could make a massive difference, many to one on rope. I meant to try this out on cardboard years ago but just never got around to it. The point I was trying to make in the above is that fairly low end steels can slice abrasive media better and for longer than higher end steels with more obtuse edges at finer polishes.

Ideally I would like to compare x-coarse, medium, fine on cardboard for a series of knives and show where the performance overlaps, how much finer can S30V be and still out cut AUS-8A. CRK&T really need to work on initial sharpness though as with the stock edge, the Zytel model only made a few cuts on cardboard before it just slipped off and could not cut anything. This would have pretty much cemented the opinion of it as a low grade steel. Too many people are not willing to experiment with profiles and grit finishes.

I have wondered about those M-16's. There are numerous models and it gets confusing.

I wish they would stamp the steel and hardness on the blade, especially when you make a dozen almost identical models with radically different steel types. I didn't think much of it on first inspection as in general I don't care for speed hole designs and it has several attributes which are problematic such as the notch in the handle for the lugs which serve as blade stops which do nothing for ergonomics, the opening is awkward, and the speed holes in the grip have many disadvantages.

However the basic ergonomics are decent and the security solid as well. The lock strength and security are likely problematic based on what I have seen with the Point Guards and the responce of the Zytel one to just light impacts, but I'll check this in more detail before I make any concrete conclusions. The cutting ability is fairly solid though in both the plain edge and serrated section and they have a nice sweep with the tanto geometry.

As a caution, the primary edge was actually hollow ground which leaves the very edge likely weak, this was ground down to flat before the above work was performed. This didn't take very long on the x-coarse side of the stone, a minute or so.

Have you ever tested a teflon coated blade?

Friction on blades generally isn't a huge factor in the force during cutting aside from certain materials. I ran some trails a few years back with chopping blades both lubricated and not and could see no significant difference. It depends a lot though on the style of knife, some knives don't bind heavily on the flats due to the way they are ground as they wedge materials open, so if the sides were coated or not it would make no difference. It isn't difficult to check though, if the performance was real all the companies would have to do was make a few cuts through poly, cardboard and wood and show the difference in force. It would cost just a few hundred dollars or so to set up the necessary force probes and have a nice series of graphs to make the point fairly strongly and appear decently high tech.

No, pm's, I'll drop you an email shortly.

-Cliff

 

[db]

DO you know or have you ever tested a chisel edge and a V edge at the same angle, to see if there is any difference in strength or edge holding? I do think chisel edges cut differently but that may only be a feel thing.

 

[the possum]

I can't say I'm really surprised by these results; they match my own experience. Though I've never explored the issue in such detail.

That said, I still don't care for the "lower end steels" because my general purpose blades see more than just slicing. I still want more strength and toughness to keep from actually damaging the edge so easily. My dad gave me a Case Cheetah for Christmas, and I promptly reprofiled it with a thin coarse edge. First time I used it for something more serious than opening packages, the edge rolled terribly. I had to add a secondary bevel at a steeper angle, and now it has a hard time sharpening a pencil.

 

[Cliff Stamp]

DO you know or have you ever tested a chisel edge and a V edge at the same angle, to see if there is any difference in strength or edge holding?

R.J. Martin noted a few years back that by tilting a chisel ground knife you can present a symmetric edge profile to the media, I was doing this in the above to prevent the blades from their natural tendancy to cut sideways out of the material. I don't like them in general due to the difficult of sharpening, especially burr removal as it is difficult to get a crisp edge with honing to the back flat. It would be interesting to see how much difference would be induced in normal use and see if it made any difference as well as check left or right for a left or right handed person.

First time I used it for something more serious than opening packages, the edge rolled terribly.

There is this, cardboard and ropes are of course really soft, with a proper edge profile you can slice them for a long time even with mild steel, I have done so in the past. However the lack of strength can be very critical on other media. The above cardboard work should be supplemented by push cutting on a harder media, it isn't as easy to obtain that in bulk though in a consistent amount. I have some plywood which I will use shortly to compare these and the other blades and see how they fare.

Unfortunately you can't get the same extreme behavior on that class of cutting as you can on soft materials by going to low and really coarse edges. if you go really obtuse and polished, which is the logical step, the edges of course resist rolling very well but then won't cut anything even if very sharp. The great thing about on cardboard is that you increase both properties at the same time (edge retention and cutting ability) but they are in opposition the other way.

-Cliff

 

[Confederate]

I wish they would stamp the steel and hardness on the blade.

Me, too; however, I think this is what most manufacturers are now trying to conceal. BTW, are you talking about the actual "hardness" of the blade or the estimated hardness? Is it correct that under some circumstances an AUS 6 blade can be harder than an AUS 8? The Rockwell ratings 56-60 can cover a lot.

-Confed

 

[Cliff Stamp]

Ideally I would like to have them individually tested, but that isn't realistic on mass produced production, just the steel and aimed for hardness would be possible though.

The ranges are fairly large and they do overlap, so yes you can get an AUS-4 blade harder than an AUS-8 blade, see :

http://www.crkt.com/steelfct.html

I just heard back from CRK&T, the M16-14Z is AUS-4 and the M16-14 is AUS-8.

-Cliff

 

[blade14]

Hey Cliff,
Great review.
I have an M21-04 (the big recurve blade) that I've been very happy with. I have had some issues sharpening it though. Any suggestions for sharpening recurve blades, I haven't had a lot of experience with them.

 

[Cliff Stamp]

Recurves are problematic, you need really narrow stones, the Sharpmaker rods work well or the corners of benchstones. Recurves are often cut at different angles from the manufacturer along the edge which mean you need to rip off a new angle with an x-coarse stone to even things out before sharpening.

Here is the work on 1/4" cardboard, same cutting, this the is average of three runs, again a mountain of cardboard cut, cutting was stopped this time after finally the edges lost all shaving ability. They could still slice newsprint and were not close to ripping the cardboard :

http://i7.photobucket.com/albums/y269/CliffStamp/crkt/m16 zytel/m16_card_quarter.png

In this run the AUS-4 version is actually slightly ahead of the AUS-8 one initially, but the difference is smaller than the random variance. Consistent with the first run, the AUS-4 version makes a larger jump after the first two cuts, but from that point on it is not significantly different from the AUS-8 blade.

So basically I would conclude that at coarse edge finishes, on slicing soft media, there is no significant difference seem in edge retention up to the point at which the blades stop being able to shave in these two knives. The AUS-8 blade should have more wear resistance so if the curves were to continue it may flatten more, I would expect this, but I'd want to run a comparison before betting on it.

A comparison at a finer finish should show the same behavior with much less cardboard, I'll take a run at this shortly, and definately include a benchmark here, probably the fine side of the same stone and check against vg-10. You also need of course to check against a hard medium as well to check edge retention on high polishes for push cuts. I'll check that later.

-Cliff

 

[kel_aa]

You defined the edge as coarse, done on a stone of about 90 grit.

Can this level of finish be achieved with the Sharpmaker? Is even brown rod corners miles away?

Also, say you keep sharpening away with a particular surface (corner or surface) more than you need to. Does this make the edge finer or does it practically level off after a certain number of passes?

Also, is lighter pressure on the brown rods equivilant to using the white rods?

It is hard to reconcile the results to our every day use knives, considering most of us pride ourselves with getting a nice fine edge. If you were to do the same test with a finer edge, would you expect to see better inital sharpness that rapidly degrades, falling behind that of coarse edges?

 

[Cliff Stamp]

You defined the edge as coarse, done on a stone of about 90 grit.

Can this level of finish be achieved with the Sharpmaker? Is even brown rod corners miles away?

The brown rods are fairly fine in general, the coarse side of that benchstones is about 140 microns according to Steve's table, the Sharpmaker mediums are about 12.5.

Also, say you keep sharpening away with a particular surface (corner or surface) more than you need to. Does this make the edge finer or does it practically level off after a certain number of passes?

It depends on the abrasive, waterstones and ceramics and diamonds tend to provide a constant level of abrasion, arkansas stones and other similar tend to smooth out with use and can get finer, generally though you end up with really slow cutting speeds and risk of reformation rather than abrasion.

Also, is lighter pressure on the brown rods equivilant to using the white rods?

Generally stones will cut to maximum under even light pressure as they are so much harder than steel.

If you were to do the same test with a finer edge, would you expect to see better inital sharpness that rapidly degrades, falling behind that of coarse edges?

Essentially yes, they will cut smoother initially, but rapidally fall behind, the difference in edge retention can be huge, as in more than ten to one.

-Cliff

 

[Cliff Stamp]

I ran a trial with the M16-14Z, Point Guard and Temparance sharpened at 15 degrees included, freehand. The edges were cut with the 90 grit side of the stone and then deburred with the 600 grit "fine" side which is still really rough. Quarter inch cardboard was cut in the same manner, 3 cm section of blade cut on a draw. Only two rounds could be done with each blade so the results are a little scattered but still interesting :

http://i7.photobucket.com/albums/y269/CliffStamp/crkt/point guard/card_pg_m16_tm.png

Assuming the initial blunting is more deformation and the later tends to be dominated by wear resistance then the order should be Temperance, M16-14Z and Point Guard early, with the Temperance being more ahead of the M16-14Z than the M16-14Z is of the Point Guard, due to the relative difference in hardness, and that indeed is what happens.

In order to actually model the behaviod I switched from splines and just used piecewise quadratics, I left them as different colors to show clearly the distinct behavior in the early and late stages of blunting. You could maybe use the coefficients to estimate the compressive/torsional strengths and wear resistance but I would want more points on the graphs to really do that confidently.

The curves tend to get the points well, the last point of the Point Guard is a bit interesting, it could show the differnce in wear resistance as both the Temperance and M16-14Z are slowing down again in the late region and the wear resistance of both would be expected to be over the Point Guard. However it could be just a random upsweep, if it was consistent over 3-4 runs I would be confident enough to predict behavior, but two runs isn't enough.

What it does show however is a few interesting points, it tends to support the deformation/wear resistance idea and shows that even if you go to really coarse finishes there are still significant benefits to harder and more wear resistant steels as even though the Point Guard cuts a lot of cardboard at this angle and finish, the Temperance is still very much ahead.

In regards to sharpening, the Point Guard was the easiest to machine, but I was using really coarse hones to reset the bevels so this didn't tend to make much difference even with the cheap hone I was using, with a 200 silicon carbide waterstone, all blades would be reset trivially. It was much easier to remove the burr on the Temperance.

-Cliff