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Thread: Lum Chinese : some hemp cutting and commentary / discussion

  1. #1
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    Lum Chinese : some hemp cutting and commentary / discussion

    I have done a decent amount of cutting on cardboard (http://www.cliffstamp.com/knives/reviews/cardboard.html) and decided to do a little rope cutting as well to check a few issues.

    The method is very similar :

    -edge angle is 4-8 dps
    -microbevel is 25 dps/600 DMT
    -3/8" hemp cut on a 2" draw (alternate directions in subsequent cuts)

    The sharpness was measured by cutting light cord under tension and using the length of draw to set the sharpness. Both 25 and 50 gram loads were used to allow measurement of high sharpness to decent precision as well as extended use to low stages of sharpness.

    The force to cut the hemp can't be used to measure sharpness because of the very low precision and very high variability. To be specific this is the force used to cut the hemp (measured on a standard scale).

    001, 4.5 lbs
    003, 5.0 lbs
    009, 5.0 lbs
    021, 5.0 lbs
    033, 5.0 lbs
    045, 5.0 lbs
    069, 5.0 lbs
    093, 4.5 lbs
    117, 5.0 lbs

    The problem is that when the knife is fully sharp it takes a tiny amount of force to make the cut, the rest is just wedging. But the scale is at best +/- 0.5 lbs. Even if you have a more precise scale, just try to make a cut with less variability than that small amount.

    Based on the fact that the knife starts to cut before the needle even moves I would estimate it takes on the order of 0.1 lbs to make the cut, this is the sharpness, the rest of the force is just wedging. However the minimum significant difference on the scale is 1 lbs. This means all sharpness reading between 100% of optimal and 10% of optimal show the same on the scale.

    It is obvious that the sharpness of the knife is decreasing during the cutting, even if you ignore the thread cutting measurement. You can see the difference on paper, with checks on shaving, and even see the edge start to reflect light but the very poor precision of the scale prevents measurement. It is a simple matter of the math of significance of measurement.

    Here is the result of one run using the above measure of sharpness (the yellow is the 25 gram load, the blue is the 50 gram load) :



    A few observations :

    -as expected, follows the same pattern/curve as cardboard
    -the 25 dps edge shows little deformation/chipping

    Note that once the knife has entered that long plateau region the rate of blunting is very low and thus very high hemp counts can easily be produced. For example in the above it takes ~150 cuts to make a decrease of 1% of sharpness in that plateau region.

    To clarify this is one run which is why the error bars (scatter) is so high, these will reduce significant as more runs are added and once 5-7 runs are completed the curves get very smooth and the scatter is much more contained.

    I also spent some time to write some code to allow comparisons, here is comparison of a O1 blade and a 10V blade :



    It shows the plots with the high force measurement and also shows the difference in sharpness between the blades as cuts are made. Note how the sharpness difference gets very small as the cuts increase, it has to, this is just the nature of the curves.

    Of course with one run it isn't possible to make anything but very coarse distinctions, it takes 3-5 runs to even see moderate differences in steels. This is just a consequence of how random errors propagate, in short they add up.

  2. #2
    Spyderco Forum Registered User Blerv's Avatar
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    How did you find the handle during the testing?
    Blake

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    Blake,

    To be frank, I never really bought the Lum as a user, but more as a functional dress knife. The Paramilitary I carry speaks loudly as a weapon to many people and I wanted a clipit which was a little more friendly. Now the handle/blade was obviously designed to give a very specific look when closed and even when open flows into a very graceful curve and this also is not well suited to a hammer grip as it is open in the middle of the hand.

    However I didn't really ever intend it to be used in a heavy hammer grip, it is also very thin for that kind of use. In a side pinch grip and in general for light use it does ok, aside from the inside of the scale could use a serious rounding which I will do at some point when I take it apart. As a direct consequence of flattening the grind and taking it to a full zero with a light convex this reduces the force in cutting to minimal levels and thus the ergonomics are greatly enhanced.

    To be specific, just think about the fact that I can cut 100+ pieces of rope and even when restricting the cut length to 2" the force is only 5 lbs which generates only a small amount of pressure on parts of the hand so it is very comfortable.

    The funny part about the whole thing was again I bought it as a clipit and with a short period of time I caught the clip when it was in my back pocket and ripped it right off so now I just do deep pocket carry which is amusing anyway. It is more useful then I thought it would be, and it makes a nice conversation piece, aside from the fact it is unfortunately black (which again people think = weapon), and I may have it clip modified at some point.






    An updated chart with some statistics on the performance :


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    Spyderco Forum Registered User paladin's Avatar
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    The handle was only able to cut the hemp when 10,000 metric tons of force was applied
    Have Kiwi, will travel...wire Paladin...Hotel Carlton, San Francisco

  5. #5
    Spyderco Forum Registered User Blerv's Avatar
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    @Paladin Lol! Nice one

    @Cliff: I do recall you saying that it was a classy purchase to deviate from the typical "scary" response amidst non-knife folk. Also, I know you are very critical of ergos so it's nice to hear the elegance holds up to more than a camera lens. I had a Lum for a while (ZDP sprint) but gifted it before I probably knew better. The CF seems it would be a bit more comfortable as the Cricket in the same material I have is surprisingly grippy for a non-textured material. It also seems quite durable; prob the best of the small Lum Chinese so far.

    As for your cutting data, great performance for such a pretty knife . It always surprises me how much material "normal" steels can do at less than crazy angles.
    Blake

  6. #6
    Spyderco Forum Registered User 3rdGenRigger's Avatar
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    Quote Originally Posted by paladin View Post
    The handle was only able to cut the hemp when 10,000 metric tons of force was applied
    That made me snort Rye Whiskey and Coke right out my nose...uncomfortable at best. I have no doubt it'll still give me a fair chuckle when I wake up and read it again.

    Edit: My sinuses are insisting that this becomes a quote in my signature, due to outright hilariousness and involuntary rye whiskey based sinus discomfort.
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    Thanx Cliff.

    I really appreciate the sharing of testing and info that we are priveledged to have. Guys like you and Jim really add to the value of our forum.

    sal

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    Quote Originally Posted by Blerv View Post
    It always surprises me how much material "normal" steels can do at less than crazy angles.
    The knife industry has some interesting adjectives for knives and steels. VG-10 for example is a very high carbon, very high carbide, very hard, martensitic steel. It was only a short time ago that ATS-34 (same class) was considered so extreme that only high end custom knives used it.

    Angles and the statements made on it are kind of interesting, what I would say here is go back one generation and read the standard texts there, the axe bible is a good place to start. Now ask yourself the following question, how come a generation later, with all the advancements in technology and steel that I am putting a higher angle on my folder than were used on felling axes?



    Sal, thanks.

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    Wait, let's not get distracted from the main point here: What were you doing putting coke in your whiskey!?

    Thanks Cliff for the testing data, this forum thanks your wrists.

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    Quote Originally Posted by tvenuto View Post

    Thanks Cliff for the testing data, this forum thanks your wrists.
    High performance grinds = low stress cutting.



    The interesting thing to me is this stage, the very early stage of the experiment where you still don't know where the data is going to end up and each time you do a run it significantly adds to the knowledge. In later stages you are just refining, reducing the uncertainty and strengthening the conclusions. This is necessary yes, you have to do it sure - but it isn't as exciting as the first trials where the seeds of knowledge are planted and you are watching them grow.

    There are also questions raised and that is the interesting part as well, for example in these trials there is almost no damage to the edges at all. This is very different from the cardboard cutting which will easily damage edges. The hemp doesn't show any difference between low and high carbide in this regard, they are all not effected. However is this because :

    -hemp is so much easier to cut than cardboard

    -25 dps is such a high microbevel that it stabilizes the edge even with very high carbide levels

    I believe it is a combination of both factors but to confirm requires further experimentation. It also raises a few more interesting questions :

    -can the edge bevel under the micro be brought lower

    This would increase the cutting ability (and ease of sharpening). However on cardboard it can't. If you dip under 4 dps it doesn't matter if you run a micro or not, you are at risk of just tearing the micro-bevel right off once you run 2-3 dps edge bevels. But again there is so little damage here it might be possible to run very low angles on hemp.

    To me, for what I do, this cutting isn't representative of regular use because it is simply far too low stress, but it is an interesting exercise. As well any kind of cutting (or use in general) if done in a careful and considerate manner can and should yield useful information.

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    Cliff, I'm curious if that's vg-10 or ZDP, and would that thin of an edge be ok for light to medium pressure cutting with vg-10 in a DF2? No crazy hard or abrasive materials
    "The skeptic does not mean he who doubts, but he who investigates or researches, as opposed to he who asserts and thinks that he has found."
    - Miguel de Unamuno

    Military Black G-10 DLC, Byrd Meadowlark 2 G-10, Lil Matriarch, Pacific Salt SE yellow, Endura 4 ffg brown, Native FRN PE, Dragonfly 2 Orange, Ulize, Sharpmaker and UF rods. Also, Cold Steel Voyager XL Clip PE, Kershaw Volt II (on loan), many fixed blades, and a KP strop block.

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    Quote Originally Posted by RealKnifeUser View Post
    Cliff, I'm curious if that's vg-10 or ZDP ...

    VG-10, I will do ZDP-189 shortly, I also finally rounded up a k390 custom.


    and would that thin of an edge be ok for light to medium pressure cutting with vg-10 in a DF2?
    I generally carry two classes of knives with me :

    -fine cutting
    -utility

    The fine cutting ones are all zero-ground. They are separated into two groups :

    -primary angles of 2-3 dps
    -primary angles of 4-8 dps

    The first ones are used on papers, foods and fairly soft material. I occasionally push them past that but I have yet to find anything that can work with that low of a primary grind and cut even hard cardboard or ropes and not risk buckling the micro-bevel.

    The second group are used on pretty much anything, cardboard, zip-ties, woods, etc. . However I don't side load them, twist them after cutting into knots, etc. . That is beyond cutting and into utility type work. I also don't cut metals, gyproc and such materials due to the high point loads they can generate or work on very dirty materials (carpets and similar).

    The other type of knife I carry will have an actual edge bevel you can see (thickness as high as 0.015") and the edge bevel will be 15-20 dps. This isn't a knife as much as it is for scraping, prying and similar. I carry an XM-18 for example as that kind of knife. It also cuts the dirty carpets, cuts cardboard which has staples possibly hidden, etc. .

    Now these are just general statements, at times I cycle them outside of that use to keep checking how much I think I know vs what actually is true and to check new steels/HT's and consistency checks. Plus sometimes I carry very inexpensive knives (I got a half dozen < $5 knives for Christmas, I zero grind them and use them for everything).

    In short, yes, the grind isn't fragile.

    I would suggest to pretty much anyone to take a knife like the SuperBlue Delica, zero grind it and just explore where it gets damage. This will do two things :

    -if you are willing and have a bit of thought/care you can also develop cutting skills

    -you will likely figure out that you can run your knives with a lot less metal at the edge than you thought

    Plus as an aside, the SuperBlue Delica is one of my favorite working knives and if everyone buys a pile of them hopefully Spyderco will make more knives like that and less of the weeaboo/tacticals. Lynn Thompson owns that market (for working, KAI for show) and I would rather not see Spyderco move towards it. But if it is your thing, its your money, everyone has their idiosyncrasies. I think Bruce Campbell should star in pretty much every movie.

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    Thanks for the reply Cliff, I appreciate it. I've been doing a lot of reading on your site and posts here, and really like the way you present your findings in a standardized format. Your info itself is exactly the kind of stuff I look for. Performance-based writups and posts like this are what give very real and useful info that can be very hard to find on my own. I have a set of DMT diasharps on the way to my house (should arrive monday) and am very excited to start experimenting with stuff like this. Thanks again
    -Ryan
    "The skeptic does not mean he who doubts, but he who investigates or researches, as opposed to he who asserts and thinks that he has found."
    - Miguel de Unamuno

    Military Black G-10 DLC, Byrd Meadowlark 2 G-10, Lil Matriarch, Pacific Salt SE yellow, Endura 4 ffg brown, Native FRN PE, Dragonfly 2 Orange, Ulize, Sharpmaker and UF rods. Also, Cold Steel Voyager XL Clip PE, Kershaw Volt II (on loan), many fixed blades, and a KP strop block.

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    Quote Originally Posted by RealKnifeUser View Post
    Performance-based writups and posts like this are what give very real and useful info that can be very hard to find on my own.
    Ok, now it's my turn to snort Coke and whiskey out my nose (not really, this is South Carolina, where Pepsi comes from). I don't think I've ever seen this directed at Cliff's writings, and I've been reading them for a long time. Not that I don't agree with RKU's sentiment, I just don't think I've ever seen it in writing.

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    Hey Ryan,

    I would suggest a loupe, maybe 10X-12X. Studying an edge with a "super eye" helps learning.

    sal
    Last edited by sal; 03-09-2014 at 04:10 PM. Reason: spelling

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    Quote Originally Posted by me2 View Post
    .... I just don't think I've ever seen it in writing.
    That's only because you don't hang out with the cool kids and instead spend all your time trying to work harden your H1.

    Quote Originally Posted by RealKnifeUser View Post
    I have a set of DMT diasharps on the way to my house (should arrive monday) and am very excited to start experimenting with stuff like this.
    I would appreciate hearing about your results, I have been using the DMT's for a long time though recently I have come to favor the Atoma's for the consistency of the diamond abrasive, but they are only available in the more coarse grits.

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    Hey Cliff,

    What are your thoughts on CBN?

    sal

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    Ok, I have a 6x2 Xtra Coarse and a 6x2 Fine/Coarse combo stone. The Atoma 140 is something I'm hoping to get in the future for really fast reprofiling/ damage repair. I watched a couple videos, and the cluster idea really makes sense. More diamonds bunched into little dots would put more pressure on smaller indevidual areas, I think. Just what I've reasoned. By the way, I'm very new to freehanding but can put a clean sharp edge on kitchen knives and softer steels with concistency using jdavis882's videos. I only have one Ace hardware 6x2 coarse/fine aluminum oxide stone right now. Hopefully the DMT's, 2 Spyderco's and a CS Voyager XL get here Monday

    Sal, thanks for the sugestion, I think I'll order one monday. I would really enjoy a very close view of the edges. By the way, I really enjoy your 3 designs I currently own Sal, they're like an extention of my hand, and I love the performance. Thanks for the reply, its very nice to hear from you.

    -Ryan
    Last edited by RealKnifeUser; 03-08-2014 at 09:27 PM.
    "The skeptic does not mean he who doubts, but he who investigates or researches, as opposed to he who asserts and thinks that he has found."
    - Miguel de Unamuno

    Military Black G-10 DLC, Byrd Meadowlark 2 G-10, Lil Matriarch, Pacific Salt SE yellow, Endura 4 ffg brown, Native FRN PE, Dragonfly 2 Orange, Ulize, Sharpmaker and UF rods. Also, Cold Steel Voyager XL Clip PE, Kershaw Volt II (on loan), many fixed blades, and a KP strop block.

  19. #19
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    Quote Originally Posted by sal View Post
    ... CBN?
    As an abrasive?

    The main promoted advantage is vs diamond as it doesn't have the carbon diffusion wear influence of diamond and it grinds cooler. However if you read the literature this is only a factor for power grinding, there are no studies showing that the carbon diffusion is a significant factor in slow speed grinding with coolants/lubricants as would be found on proper benchstone use.

    As a grinding abrasive much is made about the cutting speed of diamonds but the reality is that a coarse benchstone in aluminum oxide or silicon carbide will be much faster because you can simply press very hard and fresh abrasive is released. The only issue is wear and the required stone maintenance.

    However a diamond (or CBN) plate is very nice for finishing due to the lack of issues with swarf and the effect it has on the edge and the fact that the stone doesn't wear and thus induce angle/curvature changes to the edge. I currently use a fine DMT, x-fine Atoma and mxf DMT for various finishing edges.

    CBN is an interesting abrasive to be considered for use in benchstones, the problem is cost hence it is used as a coating vs solid benchstones and it is likely that it has the same limited life as diamond coatings. However CBN benchstones are not readily available unless you buy directly from a factory and you need substantial orders.

    CBN would be an interesting material for waterstones as it would allow a stronger binder to be used because of the lower rate of wear vs traditional abrasives. This would allow the advantages of water stones (release fresh abrasives) but reduce the disadvantages as they would take far longer to wear/hollow and of course they cut even very high carbide steels readily.

    Quote Originally Posted by RealKnifeUser View Post
    The Atoma 140 is something I'm hoping to get in the future for really fast reprofiling/ damage repair.
    A decent coarse waterstone is faster and much longer lasting, if you are willing to maintain the stone (keep it flat).



    Here is a comparison of the Lum (VG-10) and mule in 121REX. The interesting thing is that the 121 REX does have a faster initial rate of blunting but eventually it catches up as the more it blunts the more it improves relative. Now this is what you would expect and it is often the promoted advantage of high carbide steels.

    The problem is that by the time it happens the knives are very dull, you can easily draw it across your skin for example with no fear of cutting it, long past the point where it would squash a tomato vs cut it. However if you are willing to press hard and the material being cut is rigid there is still an ability to work at this stage.

    Again though, there is only 2 runs with the VG-10 and 1 one with the 121REX in the above graph. To have a decent conclusion strength you want at least 3-5 runs in each.

  20. #20
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    Thanx Cliff. We've got some CBN Triangles for the Sharpmaker that just came in. Should be shipping them shortly. I liked what I found when testing, but I wanted some additional "real world" testing.

    Let me know if you want a set to test?

    sal

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