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Thread: Preferred RC Hardness

  1. #21
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    SpikeC's Avatar
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    I have a set of Sorby chisels that have the dimple from the hardness tester, but the hardness is not uniform throughout the tool. The cutting edge had to be ground down before the actual hard metal was reached. Whether that was from initial grinding or burnout at the edges during heat treat is the question. The hardness tester only tests one point, is the point here, I think.
    Spike C
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  2. #22

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    Decarb frpm the heat treat most likely.
    Quote Originally Posted by SpikeC View Post
    I have a set of Sorby chisels that have the dimple from the hardness tester, but the hardness is not uniform throughout the tool. The cutting edge had to be ground down before the actual hard metal was reached. Whether that was from initial grinding or burnout at the edges during heat treat is the question. The hardness tester only tests one point, is the point here, I think.

  3. #23
    Marko Tsourkan's Avatar
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    Quote Originally Posted by ajhuff View Post
    ...

    I still have problems with Rockwell reporting. I remember my standards were +/- 0.5 at best, example 50 HRc +/- 0.5 would be scribed on the side and the dial had 5 unit increments if I remember correctly, 90, 95, 100... etc. The machine didn't have the resolution to differentiate between 60 and 62 nor the tolerance to do so either. This was on my old Wilson unit. Maybe those fancy digital ones are a whole 'nother ball of wax.

    -AJ
    Wilsons analog or digital (mine is analog about 20 years old) if well calibrated, will get you pretty accurate readings - +/- .25 or less. Helps to have test blocks to check on accuracy periodically and to have replacement indenters, should the one in the tester wear out, as that will throw off your reading. I typically take 5 readings and average.

    M


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