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Basic Blade Geometry.

Discussion in 'Knives' started by JonSidneyB, Jan 25, 2014.

  1. Ted Andkilde

    Ted Andkilde Loaded Pockets

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    This should definitely be a sticky when it's completed Jon, subscribed.

    Cheers, Ted
     
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  2. JonSidneyB
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    I am afraid to proof read it.

    Someone point out my typos and poor sentences and I will go back and fix them. :)

    There is a lot to cover but nothing complicated and it should all be easy to understand.
     
  3. kd7dvd
    • GITD Manix 2XL Owner
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    kd7dvd EDC Junkie!!!!!

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    Subscribed. And I'm not too shy to say I'm in it for the pictures. :rolleyes:
     
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  4. Xiii
    • The Omnia Paratus

    Xiii Loaded Pockets

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    Just a quick line. I work in an emergency dept and I see people almost every day using knives incorrectly or for the wrong things, from pocket knives to machetes. I should subscribe them to this thread.
    Cheers
    Xiii
     
  5. karlito

    karlito Loaded Pockets

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    "I AM A STEAK" "I AM NOT AN ARTIST" :rofl_revamped: I don't know why I found it so funny but I did.

    Anyway this is going to be an interesting thread. Subscribed.
     
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  6. hunter s gatherer
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    hunter s gatherer EDC Junkie!!!

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    Great stuff. Can't wait for grinds. I'm a lefty and most asymmetrical grinds are for the 90%ers.
     
  7. ManVsLawn

    ManVsLawn EDC Junkie!!!!!

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    If nothing else, we've found the Forum's Picasso.
     
  8. BubbaFett
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    Negative. I didn't see any eyes coming out of the side of someone's knife.
     
  9. Ted Andkilde

    Ted Andkilde Loaded Pockets

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    We could find an artist...
     
  10. New_Pollution1086
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    New_Pollution1086 Loaded Pockets

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    Great informative read. Thanks for doing this.

    T

    Sent from my LG-P769 using Tapatalk
     
  11. MJGEGB

    MJGEGB Loaded Pockets

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    I wanted to bump this thread but didn't want to do so without adding to it. I hope that is okay John. This thread has started to cover a lot of good information that is normally only discussed in knife maker forums or groups. It should be made a sticky to help teach the user community about the knives they love.

    Anyway one point that I don't believe was touched on yet is edge geometry. I'm sure John will want to add his own thoughts about this but as I said I didn't want to bump this thread without adding something new. Edge geometry is something that is often overlooked. We talk about fine edges, toothy edges, edge stability, angles, convex, v, chisel and so on but rarely if ever edge geometry. To be clear what I'm discussing is the amount of material left behind the edge. So if we look a standard SAK we would be talking about right behind where we sharpen the edge, where the polished blade meets the satin edge.

    The edge on a standard knife is referred to as the secondary bevel and above that is the primary bevel. Any part of the blade left the same thickness of the spine would be called the flats. A knife can be made without flats or a secondary bevel, but not without a primary bevel.

    Now that we've gotten some of the terms out of the way we can start to discuss this part of blade geometry. The basic concept is that less material left behind the edge equates to a better performing knife.
    The thicker the bottom of the grind is left before the maker puts on the edge the worse the edge geometry and the worse the knife will perform. To be fair I'm guilty of this myself in my haste to complete my first knife I neglected to grind the blade thin enough before putting an edge on it. This is apparently not only a common beginners mistake but an issue with a lot of production knives as well. A knifes job is to cut or to separate material. So let's take for example a standard SAK such a Cadet and ESEE Izula. We will sharpen both at the same angle down to the same grit so that both will easily push cut paper. Now we take both knives and lay a peace of paper on a cutting board and use both knives with moderate pressure to slice the paper. In this example the user is likely to see no difference in performance. If we now replaced the paper with something that extended past the secondary bevel such as cardboard or an apple chances are the user would see a difference in performance. Now a good deal of users will not think of this as a big deal but we all know a dull knife is a dangerous knife because it requires more effort, so why should a poor performing knife be any different? For all the Izula owners don't take offence I used it as an example simply because it is so popular. The Izula has a good grind for as thick as it is, there are far better examples of knives with poor edge geometry but the Izula is very popular and has room for improvement. Let's compare the edges, the edge or secondary bevel on the SAK should be very short maybe a mm or two tall, while the ESEE is much taller. The reason for this is because the SAK is ground thinner and there is less material behind the edge to be sharpened away to achieve the same angle. This is an issue that will only get worse with time. Since both knives are FFG they get thicker the farther up the blade you go. Most of you have no doubt noticed the edges on your knives thicken over time after repeated sharpening. Not all knives are equally prone to this issue, that brings us to a slightly different but related topic.

    Grinds, and grind depth. A hollow ground knife (properly done) should stay thinner longer through the blade, longer than any other grind. This means the knife can be sharpened more times before performance is greatly affected. However a hollow ground knife gives up a bit of strength to a flat or convex ground knife, they are also harder to make by hand than other grinds (I've heard they are easily accomplished by factory machines set up to grind both sides simultaneously). Grind depth or grind height comes into play as well. This is how far up the blade the primary grind goes. The larger the flats on a knife the steeper the angle of the primary bevel and the faster the edge will thicken with sharpening.

    I'm not an artist like John but I may add some visual aids if there is any interest. I hope this thread gets back on track, there is a lot of good information and much more that could be added.
     
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  12. BubbaFett
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    I'm still hoping Jon comes back to this. Love this thread.
     
  13. JonSidneyB
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    I do want to finish the first post someday. :) I have been on the forum more than I should lately but I will try and get back in here and work on it some more.
     
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  14. jabe1

    jabe1 Loaded Pockets

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    Great thread, looking forward to reading more.
     
  15. JonSidneyB
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    Actually the blade shape but not necessarily grinds used to be common knowledge and as you go back in time the more common the knowledge was. I don't mean knife makers but users often understood the best. It seems the more and more the world is becoming pre-packaged the less understanding of shapes there is. We used to have a greater number that understood blade shapes out here but that number has dropped. Many of them that understood the shapes were not neccessarily knife enthusiasts but job first then find the best tool people.
     
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  16. Slipjoint

    Slipjoint Loaded Pockets

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    As I have heard it, the stockman was designed for use around the farm when dealing with animals. The clip point was used for general-purpose cutting and fine point work. The sheepsfoot was used to trim hooves (as mentioned above) and cut leather or rope. The spey blade was kept sharp and rarely used; it's primary purpose was for castrating livestock and other small bits of field surgery (notching ears, etc).

    As Rob Simonich put it:

     
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  17. JonSidneyB
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    That is exactly right. In Dewey County the only real industry was cattle and agriculture. The only folders available in the stores were Stockman because it fit the small tasks that were done so well. There was a variety of fixed blades available in town but only one folder. At least they had the stockman in three sizes.

    I have posted what you said about a dozen times but I don't think people believed me. The three blades were also sharpened differently. The Sheep foot had the most course angle, the clip was medium, and the Spey blade was very fine and fragile but it could be fragile, it was only mean to cut flesh. This was common knowledge with almost all cattle people in the west at least up to the early 80's. I quit doing that kind of work back then and somethings might have changed with technology. I saw branding go electric.
     
  18. Slipjoint

    Slipjoint Loaded Pockets

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    Yes, I've heard this too.

    The stockman is my favorite slipjoint pattern so i try to dig up any info I can on them. I still find them quite useful even in a modern urban environment.
     
  19. JonSidneyB
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    When I did ranch work and worked the farm the stockman pattern was for the most part the only folder ever used. What changed from month the month was the use of a fixed blade. If there was something the stockman was not suited for we had a variety of specialized fixed blades to chose from.

    Another thing we did was if you were close to a barn or house you didn't use the tools you were carrying unless the job was tiny. You went and got other tools to save wear and tear on your field tools. Most of the work was done where there were no houses or buildings in site, no roads either. It seemed silly for us to use the tools we had on our person if one of the barns or tool sheds were handy.

    It happens that most of my life the knife I kept in my pocket has been a stockman and it is what is in my pocket now. I didn't carry a stockman on the Appalachian Trail, I went to a smaller single bladed knife since on a trail the need for a knife actually goes down. That was my longest period of not carrying a stockman.

    I don't have a favorite, I have always been what is most useful for what I am doing person. I used to carry a stockman because it was useful. Since I started the forum my life changed and I almost never have the need for a knife in my pocket, almost never. I carry the stockman today because it is what I have and have had it for decades. It might get used once every 3 months but in the past it was used daily.
     
    Last edited by JonSidneyB, Jun 28, 2014
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  20. Slipjoint

    Slipjoint Loaded Pockets

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    I don't use my stockman as much as I used to when I was working, but I do find that the sheepsfoot blade is ideal for opening packages, especially tough plastic clamshell packaging. :tongue: