Heat treat certification

Discussion in 'Shop Talk - BladeSmith Questions and Answers' started by HSC ///, Feb 26, 2021.

  1. HSC ///

    HSC ///

    Nov 7, 2012
    Curious if any of the outside heat treating houses provide heat treat certifications...? Asking for a friend :D:D

    But seriously, a friend who’s getting out of knife making, he’s always had his blades outside heat treated by the same outside heat treater gave me an AEBL blade and I checked it and it came out to 59.... then I took it to another makers shop and he measured 59.4

    I queried my friend who said it should be 61 or 62

    now it’s not like the blade is not usable but....

    certifications usually drive up the cost but I’m just curious if anyone has any similar experiences
  2. Stacy E. Apelt - Bladesmith

    Stacy E. Apelt - Bladesmith ilmarinen - MODERATOR Moderator Knifemaker / Craftsman / Service Provider

    Aug 20, 2004
    Many/most reputable HTers will test each blade. Most either mark the blade or mark the receipt with the test hardness. Some go as far as etching/engraving the hardness on the blade. These shops usually have far better calibrated hardness testers, because they are doing industrial and often aerospace work that requires certification. I would trust the HTer's results on testing the blade over someone's home shop hardness tester.
    SBuzek likes this.
  3. SBuzek

    SBuzek KnifeMaker Knifemaker / Craftsman / Service Provider

    Dec 7, 2006
    The main reason my Rc tester is certified.
    Alpha Knife Supply likes this.
  4. JTknives

    JTknives Blade Heat Treating www.jarodtodd.com Knifemaker / Craftsman / Service Provider

    Jun 11, 2006
    Really the only thing we have found to really knock the reading off substantially is a damaged brale. But it’s quickly noticeable when you test AEBL and it reads 67rc after a 300° temper.

    I do know there is a heat treating/material supplier that does not hardness test the blades. Thy just do a set process that should get them close the what thy picked for hardness. I can’t say this is right or wrong as it’s their business. But I can say we have caught quite a few problems with a hardness test. Usually this is related to the wrong steel labeled as something else, bad steel in general or steel bought from a source that has to be therm cycled to get it to harden up.

    so all this said I would not necessarily jump on the bad heat treat band wagon. There hardness tester could of been reading high and yours could of been reading low. But all the testers are within the calibration specs of the test block used.
    Last edited: Feb 27, 2021
  5. Larrin

    Larrin KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Jan 17, 2004
    The plus or minus labeled on the block is the ASTM spec requirement, the actual block is likely much tighter in distribution than that. The block should come with the results of the test readings across the block and it is likely in a very small range. Assuming it is a high quality block of course.
    DevinT, Storm W and SBuzek like this.
  6. JTknives

    JTknives Blade Heat Treating www.jarodtodd.com Knifemaker / Craftsman / Service Provider

    Jun 11, 2006
    Hum I guess you learn something new every day. So my question then is if the block is what thy say it is on the side then why have the tolerances engraved right after the hardness value. I’m going to have to dig deeper into this and read up a bit more. I had always assumed that the +or- was the range thy certified there test number to be within.
  7. HSC ///

    HSC ///

    Nov 7, 2012

    Manufacturing tooling is often like this. I know Moore jig borers and Herman Schmidt tooling is like this. Display rated at one level and actually built to a higher tolerance level.
  8. HSC ///

    HSC ///

    Nov 7, 2012
    It’s possible but I doubt it. I have a pretty high quality Goko Seiki hardness tester. And as I said, I took it to a friends shop, Tim Wright and he’s been doing his own heat treating for 36 years.

  9. Storm W

    Storm W

    Feb 19, 2019
    I haven't specifically checked with hardness testers but I have dealt with a lot of testing equipment such as X-Ray and ultra sound ect. Certification comes from a standard and standards come with a range of acceptability and thats what you certify to. If you are having work done you can have it done to a specification and that will override the standard and it could be looser or tighter depending on your needs. If you put your specifications in writing then you can certify your person or thing to that spec. Depending on what is in your spec you may or may not be able to have another company or organization accept your certificate.
    HSC /// likes this.
  10. NYMet


    Aug 5, 2014
    The plus or minus tolerance on the hardness blocks are there for machine to machine variations. The data you see from the block manufacturer is the readings they got on their machine. If you test that block and fall within the plus or minus it means your machine is within calibration of their machine within expected differences. your 59 could be someone else's 61 and that is ok. That is the worst case scenario but it is real and acceptable to testing standards.

    ASTM has re-testing tolerance standards for other things like chemistry, dimensions, etc. When re-testing anything you cannot expect to get the exact same number but should get a number within a reasonable and accepted limit.
    DevinT and Natlek like this.
  11. DeadboxHero

    DeadboxHero KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Mar 22, 2014
    It's a big reason why I do my own HT, I feel some of the details get watered down when you pay someone to do batches with something so sensitive.

    Surface flatteness, decarb removal and finish are key yet there are all kinds of goofy things going on out there in the wild.

    Best Practices aren't as common as one would think.

    Assume nothing.


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