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Quick: Hardening & tempering 4140?

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  • Quick: Hardening & tempering 4140?

    I'm doing a last-minute Christmas present- a body hammer made from a bar of 1.5" 4140. I'll be affixing it to a small fiberglass handle meant for a ball-peen (if I can find one. )

    I'm guessing I need the faces hard and the body medium-soft. I have no furnace or forge, but I do have a big oxy-acetylene torch. It's also a body hammer and not a carpenters', so there's less pounding and more tapping.

    The 4140 is annealed- at least soft enough the suppliers' bandsaw could cut it fairly easily.

    Any recommendations on the proper- or adequate- procedure for hardening the faces and/or tempering 'em? I have a gas torch, a bucket of water, a pan of oil, even some nice cool snow.

    Doc's Machine. (Probably not what you expect.)

  • #2
    Hi Doc- for a quick reply and, maybe that is all this is worth!
    I'd be afraid that someone might misuse the hammer and if it was too hard, crack/chip/shatter, but here is my reply.

    I'd heat the material until it looses it's magnetism and quench it in oil, then stick it in the oven with the wife's Christmas ham to temper.
    Baring the ham soak, then, I'd heat it to about 500 degrees and surround it with something like sand to hold the temp until it cools.
    After it cools, check it with a file to make sure it is not too hard.

    At GM, we hardened transfer punchs (drill rod) by heating and dipping them in bees wax until cool. We never did temper them and never had a problem with them shattering either. Just my guess tho' on procedure-Jerald


    • #3
      The 4140 will get mid 50s max on the Rockwell "C: scale unless it is run through a carburizing process. Tempering at 400F for and hour or two and let cool in air should bring the hardness down to about 40RC. For light tapping work on body sheet metal it should be alright but I do think that most hammers are made out of a "S" series tool stool. S of course meaning shock
      Forty plus years and I still have ten toes, ten fingers and both eyes. I must be doing something right.


      • #4
        Body hammers I'm familiar with have relatively thin sections where the heads are mushroom, wedge or spike shaped. You could heat treat whole head in the usual fashion.

        Or you could locally heat treat the heads and let the body run soft.

        I've done similar work where I heated the whole part and quenched only the part that needed extra hardness. The body would normalize to Rc 30 to 45 depending on the heft of its section while the hardened part when to max for 4140 - about Rc 52 to 55 a hardness you could barely file. Then I'd lay the part inside my tempering oven - an old rusty hunk of hollow marine shafting a foot long that I'd previously heat to the tempering temperature with a weed burner torch and check with a Tempil Stick. I'd stuff the ends of the hole with fiberglass house insulation. The mass of the shafting ensure a long tempering cycle and a slow cool.


        • #5
          4140 is cro-moly right?


          • #6
            Google on "4140 steel" from first site:

            WORKABILITY - Alloy C4140 is an oil-harden
            ing steel of relatively high hardenability. Its chromium content provides good hardness penetration, and the molybdenum imparts uniformity of hardness and high strength. C4140 responds well to heat-treatment and is comparatively easily machined in the heat-treated condition. With a combination of such highly desirable properties as good strength and wear resistance, excellent toughness, coupled with good ductility, and the ability to resist stress at elevated temperatures.le on 4140 steel:


            • #7
              I harden 4140 with a torch HOLD the flame still until you see what appears to be a flowing looks like water and then slowly move the torch in the direction desired. I use this procedure on die components and never had a wear related problem.


              • #8
                This may or may not help you but......

                I made fireamrs engraving chisels out of S-5 tool steel. If your 4140 is indeed an S series steel you might try what I did.

                I torched the chisel tips until they were cherry red (starting to look liquid) and held them there for two minutes. If memory serves me right, it was 15 minutes per 1inch of cross section for the heat soak. Then I quenched them in 10 straight weight room temperature Pennsylvania (parafin base and not sulphur base) motor oil until room temperature. Quaker State or Penzoil will work fine. I lowered the chisel to the center of a campbells chicken soup can filled with this oil and DID NOT SWIRL IT TO ACCELERATE THE COOLING. This creates a hot jacket around the chisel. This left the chisel self-annealing and ready to use once the carbon was cleaned up off the face. The chisels were pre-worn useing 4/0 emory paper. S% is a great tool steel for the backyard mechanic working with a propane torch! good luck
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