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Recommendation? Failure... Time to try again 5160

Discussion in 'Shop Talk - BladeSmith Questions and Answers' started by Wags1776, Apr 20, 2017 at 4:23 PM.

  1. Wags1776

    Wags1776

    5
    Thursday
    Hey anyone, I just finished my 4th attempt to make a knife... because It warped and cracked during heat treat. At school, we have a nice machine shop and I've made a few simple stock removal knives. The first a straight razor which came out beautiful and straight, but was accidentally thrown away over the summer. A small knife with a convex grind and paracord wrap I gave away. A small edc knife which was lost/stolen and finally by beautiful 10.5" bowie that has a serious warp and structural cracks down the spine. So its time to try again (making a big bad blade), but before I start I have a few questions:

    1: What went wrong?
    - I didn't normalize but didn't think I needed to for stock removal
    2: What steel?
    - I liked working with o1 but I feel betrayed by it, would 5160 be easier for me to heat treat for a big chopper?
    3: Any Misc advice for a newb?

    Thanks
    -Bret
     
  2. R.C.Reichert

    R.C.Reichert

    764
    Jul 26, 2008
    Are you using warm oil for quenching your blades? Also, I think if you overheat the steel before quenching could cause a similar problem also, but I'm no expert.
     
    Last edited: Apr 20, 2017 at 4:36 PM
  3. kuraki

    kuraki KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Jun 17, 2016
    It's not enough information for any helpful answers. What was the heat treat procedure? What was the oil it was quenched in? How much grinding prior to quench? How was it quenched? Where are the pictures of these cracks?
     
    Don Hanson III and R.C.Reichert like this.
  4. Wags1776

    Wags1776

    5
    Thursday
    Oil was room temp, I used an oven so I doubt the blade got too hot.
     
  5. R.C.Reichert

    R.C.Reichert

    764
    Jul 26, 2008

    I always warm my oil to 130°f before quenching.
     
  6. Wags1776

    Wags1776

    5
    Thursday
    Sorry for the lack of detail. I took the blade to 1475 for about half an hour then room temperature oil quenched. As per the recommendation of our resident machinist. Lots of grinding prior to quench, I ground the whole blade from 1/4 inch stock. Probably should have done a normalizing cycle or 2. [​IMG] [​IMG] [​IMG] (not sure if the image will work) http://i.imgur.com/LZ1cmxA.jpg , http://i.imgur.com/r3XaTvq.jpg
     
    Last edited: Apr 20, 2017 at 5:22 PM
  7. kuraki

    kuraki KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Jun 17, 2016
    This crack is propagating from the spine? How thick is it at the crack at the spine and how thick at the edge? How long is it to either direction from the crack?

    [​IMG]
     
  8. kuraki

    kuraki KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Jun 17, 2016
    [​IMG]

    To get these to post you need to paste the link like this:

    Code:
     [img]http://i.imgur.com/r3XaTvq.jpg[/img] 
     
  9. kuraki

    kuraki KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Jun 17, 2016
    That crack is starting at the edge, not the spine, isn't it?
     
  10. Wags1776

    Wags1776

    5
    Thursday
    Both cracks are about half an inch, extending from the edge, it's pretty thin there.
    Thanks for the help tip on posting images.
    [​IMG]
     
  11. kuraki

    kuraki KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Jun 17, 2016
    I'm wondering how thick the spine is and how fast the quench medium is because cracks like that I believe come from the edge cooling much faster than the spine. As the edge cools it contracts slightly and hardens while the spine is still hot and plastic. Then the spine cools and contacts, and tries to pull the edge around it, but being hard already, it cracks from that stress.
     
    Wags1776 likes this.
  12. Don Hanson III

    Don Hanson III KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Oct 3, 2002
    Edge probably too thin. 30 minutes maybe too long a soak. Oven temp maybe wrong.

    Blades in after oven reached temp, or in while oven came up to temp?

    I made hundreds of blades from 01 years ago and never had any cracks.
     
    Wags1776 likes this.
  13. Stacy E. Apelt - Bladesmith

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

    Aug 20, 2004
    I agree, something is wrong. Those edge cracks would normally show from doing a thin edge in a too fast a quenchant. I get them when doing W-2 slicers quenched in water/brine. (That's why I recommend doing a W2 quench before grinding the bevels)

    Is your quench tank outside where the tank catches rain water? The oil would float on it and you wouldn't know you were quenching in water. If your oil is old, possibly water contaminated, or of unknown type, replace it with a commercial quenchant or a coupe gallons of canola.



    I suggest addressing all the issues Don mentioned:

    Make a new knife in O-1 or 5160 and finish it to 400 grit. ( Both would be fine for a chopper)
    Leave the edge at .020" to .030" before HT.
    HT in the oven at 1500-1520F with a 10 minute soak. ( both steels use the same temperature range)
    Quench in 130F medium speed oil - Parks AAA or canola
    Temper immediately at 400-450F
    Finish knife and give it a good field test with chopping and cutting stuff.
     
  14. Wags1776

    Wags1776

    5
    Thursday
    Thanks for the advice, I tried to leave the edge about .03 thick, and theres no way any water got in the tank, but it's 1/4 inch at the spine with a hollow grind so the difference in cooling speed for the edge and spine would be huge and I was going into oil that was about 65 degrees.
    With that 10 min soak on a blade witht the same geometry as this one theres no way the spine would get to edge temp, so are you effectivley doing a differential quench. Also would preheat or stressremoval cycles be necessary, or a second tempering cycle? Or just one to 1500 for 10 min and once to 425 for 2 hrs?
    Your advice has been extreamly helpful.
     

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