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  • #11879
    Profile photo of 74
    74
    Survivalist
    rnews

    Article by Author: Joe Talmadge

    http://www.agrussell.com/Articles/a/105/

    Welcome to the blade geometry FAQ. Our objective is to provide a working knowledge of blade shapes and grinds. After reading the FAQ, I hope you’ll be better able to answer the question, “I need to do job X, what kinds of knives should I consider?”. We will start with some general characteristics of blade shapes, then talk about blade grinds, then put it all together to discuss specific blade patterns. The last section, a brief analysis of some common designs, will build upon the previous sections. It’s important to keep in mind that the characteristics can be as important as blade shape. When you’re done with the FAQ, you should be able to make decisions not only on blade shape but on other attributes. If you need to slice, you’ll know to look for a nice curving belly — and not get hung up on what the ostensible blade shape is supposed to be.

    #11885
    Profile photo of 74
    74
    Survivalist
    rnews

    How blade sharpening angle effects cutting abilities:

    From the sharpening supplies web site: http://www.sharpeningsupplies.com/?gclid=CPmTk5uziL4CFaVxOgodwmUAKw

    Under 10 Degree Angles
    The lowest angles are reserved for edges that are typically cutting softer materials. In this case, the edges are not subject to abuse so the lower angle can be maintained without damage or edge failure. The lowest angles that we typically see are on straight edge razors. These are sharpened to an angle which is roughly 7 to 8 degrees (although the back of the blade is used as a guide so knowing the angle isn’t important and nor is it adjustable). A straight razor has a very delicate edge that is very easy to damage. In proper usage, a straight razor would never see the type of use that would damage the edge.
    10 to 17 Degrees Angles
    A sharpening angle of 10 to 17 degrees is still quite low for most knives. With a total angle of 20 to 34 degrees, this is still a very fine edge. This edge is typically too weak for any knife that might be used in any type of chopping motion. Also consider that harder steels are also more susceptible to impact damage because they are more brittle. If your knife is used for cutting soft items or slicing meats, this lower angle can hold up and provide a very smooth cutting action.

    17 to 22 Degree Angles
    A 17 to 20 degree angle covers most kitchen knives. Some knives (typically Japanese manufacturers) will sharpen their knives to roughly 17 degrees. Most western knives are roughly 20 degrees. It is our experience that kitchen knives sharpened to 15 to 20 degrees cut very well and are still durable. These angles are still not highly durable as a total angle under 40 degrees will not respond well to rougher treatment in harder materials.

    22 to 30 Degree Angles
    In this range, the knife edges are considerably more durable. A pocket knife or a hunting knife will inevitably see abuse not seen by knives meant primarily for slicing or chopping softer materials. While the edge may not ultimately be cut as well (but you may not notice a difference) it will be considerably more durable.

    Over 30 Degrees Angles
    Any edged tool or knife that is sharpened past 30 degrees will be very durable. Its cutting ability will be noticeably reduced. This durability has an advantage because more force can be used to make the cut. While the majority of knives won’t benefit from this sharpening angle, an edged tool like a machete, cleaver or axe must be durable as the typical cutting action of these tools would damage other edges”

    It’s interesting how such simple tools can have the effectiveness altered by a change of only a few degrees of angle in the shape of the edge.

    #11928
    chester
    chester
    Survivalist
    member7

    Interesting & useful topic. Thanks 1974.

    #11929
    Profile photo of matt76
    matt76
    Survivalist
    member8

    74 thanks for the article. I had never looked into why different grinds were used, I just knew what they were. This will definitely be useful building knives in the future.

    #11936
    Profile photo of 74
    74
    Survivalist
    rnews

    Matt,
    If you get into forging knives you might want this video. http://usaknifemaker.com/dvd-rob-hudson-blade-forging-to-shape.html

    I lived near Rob and had a chance to be in his shop just after he passed the guild test for Master Smith. If you look up his name you will find his knives and swords that were made at the highest level of craftsmanship.

    (Not to be confused with Robscustom knives in Pa.)

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