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Measuring Thinness Behind The Edge
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    JohnnyChance's Avatar
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    Measuring Thinness Behind The Edge

    Often we talk about how thin a knife is behind the edge and how this makes such difference in cutting ability of a knife. When we use calipers to measure knives so others can get an idea of the geometry of a blade, we often pick a spot, 2mm, 5mm behind the edge to measure from. There is no standard and I don't find the measurement super useful.

    What about if instead we started with a measurement, say 1mm, and then measured how far from the edge the knife reaches this thickness? Just set your calipers to 1mm, lock em if you can, and then put the blade in until it is 1mm thick. It is harder to measure this way, as you then need a 3rd hand and a ruler to measure how far back it is, but I think it is more useful. One instantly knows a knife that is 1mm thick 12mm behind the edge is thinner than one that is 1mm thick 7mm behind the edge. Where if you measured them 2mm behind the edge, you might get 0.48mm and 0.53mm. I dont think it tells you as much about the knife.

    So for those of you who like seeing measurements or doing your own, what do you think?
    "God sends meat and the devil sends cooks." - Thomas Deloney

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    Senior Member mpukas's Avatar
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    I think this is a great idea!

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    use a marker and "scribe the line with the calaper tip then you have no problem checking how far up the blade that thickness is

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    I do like this idea but as long as I've been on the forums, people all seem to do things their own way.

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    JohnnyChance's Avatar
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    I think I am going to try to dip a knife in a water and food coloring solution, and then "scribe" a line at a certain thickness like Butch said. Like using Machinist's Blue. I have used the food color/water solution to mark fish mouth cuts in exhaust and header tubing when working on cars.
    "God sends meat and the devil sends cooks." - Thomas Deloney

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    JohnnyChance's Avatar
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    On a whim I tried it this way: A friend held the knife (Michael Rader 10" Chef Passaround knife), while I measured where the blade was 1mm thick. Then either he or I put the tape so the bottom edge of the tape was at the 1mm mark. We did this about every 3/4" along the blade. Took a couple minutes. Later I went along and measured the distance behind the edge the tape was at.

    The measurements are, from tip to heel: 15.0mm, 17.6mm, 16.2mm, 16.2mm, 14.3mm and 10.8mm.


    Not the prettiest thing ever, but it is a work in progress, haha. Picture quality is terrible too because I took it at night in my kitchen with bad lighting.
    "God sends meat and the devil sends cooks." - Thomas Deloney

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    I still go with John Juranitschs advice which is 0.5 mm at 6.5mm.
    But i was thinking how to make it more useful, and i would say that if you keep angle as low as you can without scratching side of relief and your bevel is thcker than milimetre visually, blade is to thick. What do you think about that?

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    sorry its in inchs and i used a sharpy marker not layout dye (i jjust dont have any )

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    JohnnyChance's Avatar
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    Thats pretty cool Butch. The three levels give you a really good idea. I just didnt want to scribble marker all over Rader's passaround knife! haha.
    "God sends meat and the devil sends cooks." - Thomas Deloney

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    I just checked my latest and it is .01 thicker than Butch's at the same places. Compared to Michael's it is 1 mm thick at 11 mm at the heel, 12 mm at the mid point. and 21 mm at the tip. I guess I'm sort of in the ballpark.
    Spike C
    "The Buddha resides as comfortably in the circuits of a digital computer or the gears of a cycle transmission as he does at the top of a mountain."
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