AEB-L warpage woes

Discussion in 'Shop Talk - BladeSmith Questions and Answers' started by Hubert S., Feb 14, 2021.

  1. Natlek

    Natlek

    Jun 9, 2015
    Why you don t try to HT strip of AEB-L ? I mean you will cut/grind shape knife after HT ? It works for me , I never shape tang / say for hidden tang style knife / because I notice same thing .............
     
    Scaniaman likes this.
  2. Hubert S.

    Hubert S. Gold Member Gold Member

    743
    Dec 14, 2019
    Jarrod, thank you very much for sharing your tips and tricks so freely. I have learned a lot from your posts since I started making knives.

    I did straighten a couple of blades between quench and cryo yesterday and like you said, they bowed back. I will quit doing that and also be more careful opening the pouches. Based on one of your previous posts, I quit grinding the surface before HT a while ago and had pretty good success until yesterday when only one blade came out straight.
     
    Bigfattyt likes this.
  3. Scaniaman

    Scaniaman

    663
    Jun 15, 2012
    Yes I have thought about it. Or at least wait with the pinhole closest to blade, until after heat treat.
     
    Last edited: Feb 14, 2021
  4. Scaniaman

    Scaniaman

    663
    Jun 15, 2012
    You'll take care of it in no time. Just don't over-whack. Start easy and see what/when works. I have over-corrected a time or two..

     
  5. Natlek

    Natlek

    Jun 9, 2015
    That make sense to,with all that holes steel in handle cool much , much faster then rest of blade .
     
  6. Hubert S.

    Hubert S. Gold Member Gold Member

    743
    Dec 14, 2019
    I want to thank everybody for your help. I think I have a good idea how to get the lateral warp out. Maybe it got lost or was poorly explained, but nobody commented on the curvature some of my blades now have in the other direction. I tried to get a picture of it but it did not turn out so well, so I made the very exaggerated illustration below. Has anybody seen anything similar or am I the only one? This problem is also most severe at the tang/blade junction and it is almost like there is a kink and the tang is kicked up. I recall seeing this on one blade I made about a year ago, but back then I attributed it to a mistake in profiling the blade even though that did not seem very plausible.

    [​IMG]
     
  7. HSC ///

    HSC ///

    Nov 7, 2012
    I’ve never experienced this sort of bend or warp
     
  8. Joshua Fisher

    Joshua Fisher KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    673
    Mar 27, 2018
    I’ve been using one of Jarods straightening hammers for quite a few blades now, i don’t work with Abel but I do work with a lot of thin stock that likes to warp/move, I find it faster than trying to mess with shim tempers. If your making a hammer yourself make 100% sure that you have impact grade carbide. I recently was at another smiths shop to help teach a class and we were talking about Alabama Damascus warping and he had 2 blades only 6” in total length from tip to butt that had about 3/8” of a warp in the middle that he couldn’t figure out how to straighten, I happened to have my straightening hammer with me in my tool box so 5 minutes later I had both blades down to under 1/16” warp that he was easily able to finish flattening on the grinder. So needless to say you can get a lot of warp out if needed.
     
  9. Hubert S.

    Hubert S. Gold Member Gold Member

    743
    Dec 14, 2019
    I don't know if the piece I have is impact grade or not, I think it was labelled as C2 tungsten carbide. I can check tomorrow. Honestly, I did not know there was such a thing as impact grade carbide until very recently. Assuming I have non-impact grade carbide, will it immediately shatter?
     
  10. Joshua Fisher

    Joshua Fisher KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    673
    Mar 27, 2018
    It very well could, some grades of carbide are very brittle. I’d just be careful and make sure you have safety glasses on, I was teaching a class recently and had a student drilling a hole through a socket on a spear head and had the drill bit snap and glance off my cheek about 1/2” below my eye, jokingly told the class “There goes all of my luck for the week” was a good reminder that things happen when you least expect.
     
  11. Hubert S.

    Hubert S. Gold Member Gold Member

    743
    Dec 14, 2019
    I'm glad the drill bit missed your eye. I used to be a lot more casual about safety equipment, but I have become pretty good about wearing safety glasses in the shop, as well as a respirator and hearing protection. I'll make sure to be careful with it.
     
  12. PEU

    PEU Gaucho Knifemaker Knifemaker / Craftsman / Service Provider

    938
    Aug 6, 2006
    I heat 14C28N to 900C for 10 minutes and then to 650C and leave it to cool in the oven, greatly reduces warpage, then harden and cool in my hardening press, most of the blades come out flat, unfortunately, some don't and are hammer straightened or re hardened.

    I found that a masonry hammer with the tips slightly flattened work better than my carbide tipped slot hammer.
    As long the hammer is hardened it works. Yup, my first two hammers I bought locally were soft... ¿? weird but true.

    Pablo
     
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  13. Hubert S.

    Hubert S. Gold Member Gold Member

    743
    Dec 14, 2019
    How long do you keep it at 650°C? I assume you do this step without foil in the blade rack you showed a picture of a while back?

    I would be interested to know what the purpose of the two different temperatures is. @DevinT recommends a pre-quench from 20 minutes at 1,725°F for grain refinement before hardening. In a separate thread, he recommended a sub-critical anneal at 1,350°F for a couple of hours if the hardening occurs a significant amount of time after the pre-quench. Your temperatures are relatively close, do they serve the same purpose?

    I've been looking at your oven build thread recently, that turned out really nice. I am starting to plan for a bigger furnace.
     
  14. PEU

    PEU Gaucho Knifemaker Knifemaker / Craftsman / Service Provider

    938
    Aug 6, 2006
    It was trial and error, my idea was to do a poor HT at 850-900C and then soften the steel at 650C. What you saw with the rack was an ongoing test following some ideas from Larrin, so far so good.
    650C I leave it for at least two hours and then let the batch cool inside the oven overnight.

    Regarding the oven, it's still my current oven, purchased the same PID again to make a second one, probably this year. If you need help just post in that thread and I'll do my best to help you out!


    Pablo
     
  15. Hubert S.

    Hubert S. Gold Member Gold Member

    743
    Dec 14, 2019
    I used an old 12oz ball peen hammer and drilled a 1/4" hole with a carbide drill bit. The hole turned out a bit smaller than the carbide insert, but I was able to press it in there and it seems very solid. I tried it on a few of the blades and it is just amazing. It worked even for a 3mm thick honesuki blade that had a pretty decent warp.

    The carbide I used was indeed C2 carbide rod from McMaster. I could not find much online in a quick search about impact resistance. The piece started out 2" long, I scored it in the middle with a diamond disc, wrapped it in a rag and hit it to break it in half. It took a couple of good blows without breaking before I hit it for real and it fractured into two pieces. I think it will be fine but I will be careful with it and report here if it breaks.

    Thanks again everybody for your help.

    [​IMG]
     
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  16. LCoop

    LCoop

    440
    May 5, 2007
    I'm really curious. Most masonry hammers I have seen have like a chisel end. Do you grind them to a single point?
     
  17. Hubert S.

    Hubert S. Gold Member Gold Member

    743
    Dec 14, 2019
    Your heat treat sounds convenient, saves the first plate quench compared to what I have been doing. With my small HT oven, I try to build up a bunch of blades to do the final HT on in a single day. So I'll pre-quench and then anneal a couple of blades when I can until I have enough together and a free weekend day.

    It will be a while before I start building a new oven. I'm interested in what you will do differently for your next oven and hope you'll do another WIP thread. I like the idea of putting the coils up top like JT's and Drew Riley's ovens, it seems a lot easier to service. I dread the day the coil burns out in my current oven and I will have to replace it.
     
  18. PEU

    PEU Gaucho Knifemaker Knifemaker / Craftsman / Service Provider

    938
    Aug 6, 2006
    I had to service mine a couple of times and found no problems it was rather easy. I'm sure I'll improve on the thermocouple location, not that current is wrong, but I hit it from time to time, so I think next one will come from the top instead of the side. Besides that I'm happy with the oven.

    My hammer is not a single ballpoint but a slot, 2mm by 15mm (0.08" by 0.6") so a slightly modified masonry hammer works great. Its holiday tomorrow, on wed I'll take a photo and post it.

    Pablo
     
    LCoop likes this.
  19. Lee Hester

    Lee Hester

    64
    May 4, 2011
    How are you guys grinding the points on your carbide rod? Will ceramic belts on a grinder cut them?
     
  20. Hubert S.

    Hubert S. Gold Member Gold Member

    743
    Dec 14, 2019
    I used a diamond coated wheel in a Dremel tool. The wheels are pretty cheap at Harbor Freight. I had the carbide spinning in the drill press and just shaped it with the wheel. It is very quick to do. I then spun it in a hand held drill against a cork belt loaded with compound to polish it a bit. Maybe that did something, the surface came out pretty smooth.

    I have scratched my carbide file guide using ceramic belts, but I don't think they would grind carbide very efficiently. I am curious now, I'll try to test it tomorrow if I remember.
     
    Lee Hester likes this.

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