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  1. #1
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    Default Hardened Part Information Needed

    I need help locating options for hardening a small quantity of 4140 steel jaws to 40-45 Rockwell C.
    These are a curved hydraulic cutter jaw used for cutting vehicles. The finished jaws need to be "soft" enough that they are not brittle, and hard enough to cut thru vehicles.
    Any suggestions and help would be appreciated.

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    If you don't get a lead on somebody closer, give Metals Technology in Carol Stream, IL a try. Metals Technology

    They have a low minimum order, $20 last time I checked, and good QC. Give them a call. I have no affiliation other than being a long time satisfied customer.

    Dennis

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    40-45 Rc is pretty soft for cutting steel. I think you would be better off with something like S7.

    Tom

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    Tom,
    Steel hardness is not my forte, I was told 40-45 would work, I need hardness without the edges becoming brittle and chipping off or shattering. Do you think 57 will be best? I appreciate your input.

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    Not 57, S(as in sam)7. Its a shock steel and can harden in the 55-58 Rc range

    Tom

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    Quote Originally Posted by TDegenhart View Post
    Not 57, S(as in sam)7. Its a shock steel and can harden in the 55-58 Rc range

    Tom
    You can draw S7 all the way back to 50. Which is probably lower than I'd make any cutting edge. I would draw it at 700, which pulls it back to 53.

    I'm assuming these are like the "jaws of life" hydraulic cutters?

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    I'm with the folks that think 4140 isn't up to the task if that is an emergency extrication tool. Those things are used to cut everything under the sun, and the operators often have little to no training as to what they shouldn't try to cut. And when someone is bleeding out preservation of the tool is the last consideration. Many styles have acute angles for the shear edges, further weakening the edge.

    I'd agree with the S7. ISTR S7 has a toughness minimum with about a 800F temper, but Bryson's book doesn't fall to hand. I think I'd keep the draw down more to 500F.

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    You can get 4140 case hardened. This will give it a hard outer "skin" but retain the toughness without being brittle

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    As many have said, 4140 may not be up to the job. I'd also mention that the actual design of the jaws, including lenght, geometry of the cutting edges and support, pivot strength and stability, and even design opening and closing geometry will mater as far as how well (and long) the jaws work.

    More new cars are being made with so-called high strength steels, making jaw material and hardening more critical.

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    Is this for a Hurst tool ?

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    It is not a Hurst tool, but the operation is similar.

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    These are similar to Jaws.


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