MilwaukeeJon

Failed 1084 blade

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Forged a larger kitchen knife from 1084 this weekend and thought all was well but after sharpening and honing it is clear the blade lacks integrity. Specifically, the edge crumbles pretty badly when chopping a 1/4" thick piece of white oak (using a hewing stroke as with an axe). Also, when I polish the blade with green compound on the buffing wheel (soft) the edge shows evidence of hair like pieces coming off. Not good!

Looking back, it seemed as if the whole making process went well. however I did do a second heat treat because the quenched blade initially had a nasty warp (the straightening process involved reheating the blade to orange, bending/lightly hammering out the warp, reheating to critical and quenching again in 140m degree canola oil). It may be worth noting that the after the first quench the blade looked better, more like my other more successful blades (right color, large black flakes that came off during the quench). The second heat treat did not do the same. 

Any assistance on where you think this went wrong would be appreciated. No big deal messing up this knife and maybe I can use it for light duty work in the kitchen. But certainly am interested in not repeated whatever mistake I made. Thanks in advance for your advice. 

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What else would be helpful to know? Normalized three times before quench (10-15 minutes, heated to orange color...can say that my gas forge seemed a tad hotter than  normal). Also, I did not overheat blade during grinding/polishing.

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what is orange? and it sure sounds like over heated,  crumbles are over heated, spider webs are from cold working, any pics?

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One added bit of info. I did a 2nd tempering cycle, during which time I used a steel bar, two spacers and a C clamp to remove a small warp. In a rush to get back out to the shop I rapidly squirted the whole thing with cold water from the kitchen sink. My thought, perhaps mistaken, was that folks rapidly cool objects on which they are letting the colors run. Bad idea for me to quench right out of the 410 degree oven?

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Water quench from tempering temps makes no difference.  I would suspect either quenching from too hot of a heat, or too many cycles. Could just be decarb along the edge? 

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Hi,

A little clarity, and pictures would help alot.  When you say “kitchen knife” is it like a chefs knife or a cleaver?

How thick is the blade?

What is the edge geometry?

Did you mean to post “1/4” thick piece of white oak”?  Thats not very thick.

Not knowing any of the above information, I will say this, I’m not sure any of my chefs knives would stand up to chopping oak.

They are designed for slicing, and retention of its edge, not chopping.  Now my Bowie could chop a small tree down, but kinda suck in the kitchen!

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That is good to know, Jspool, although I did try some of my really good Japanese and German knives for comparison and they did pretty well against the oak. The wood tested is really dense white oak and even a 1/4" piece is pretty tough. 

Clearly, my initial quench failed miserably and probably due to being too hot at the start. So last week I knocked off the really nicely shaped wooden scales and ornamental pins (yes, the knife was finished before I realized the bad blade!) and heat treated all over again. Much better results this time. Still learning about 1084 and also am going to start a new quench bucket given that the other oil had been in a year and may have impurities in it that don't help a successful quench. 

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