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Thread: Heat Treat for Hardy tools?

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    The First Cut is the Deepest! Magpie's Avatar
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    Default Heat Treat for Hardy tools?

    I am in the process of making some basic hardy hole tools and am curious what you metal masters think would be a good heat treat for this purpose?

    material is old cold chisels hole size is 3/4

    First one I tried I water quenched only the working top inch, and left the base at red heat. thought it would radiate up and self temper. First strike in use it fractured, showing a very course grain structure. So this stuff gets mighty brittle.

    Any suggestions?

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    Senior Member blabbermouth 10Pups's Avatar
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    Here look at this. Charlie posted once. Basics. I think you missed some steps.

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    Senior Member blabbermouth spazola's Avatar
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    The grain will be big and ugly after forging, I would try a few or more normalizing cycles. (critical -> air cool till black)

    I heat treat my hardie/anvil tools the same as I do my razors but I temper them to at a higher temperature.

    I do not know what type of metal the cold chisels are, but I would try normalizing and see it it helps.

    Charlie

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    Senior Member blabbermouth 10Pups's Avatar
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    Cold chisels are 1045 or 1050 I think.
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    The First Cut is the Deepest! Magpie's Avatar
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    Actually did normalize (I think I did) by leaving the tool in the forge after I turned off the gas, and let it cool down with the forge. I figured that would be a nice slow cooling. perhaps too slow?

    Charlie, what temp do you take your tools to? Maybe my attempts at "auto temper" are not practical.

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    Admin & Forum fixer Bruno's Avatar
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    Auto temper works. However, you really have to know what you are doing because you have to judge initial hardness and thermal mass of the hardened area and the amount of residual heat in the workpiece and what the resulting temperatures will be when the heat migrates to the rest of the workpiece while cooling down. This is easier said than done
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    Armchair quarterback commenting: (still waiting on stuff to arrive via mail)sounds like it needed tempering. From what I have "read", you must temper, because after the quench the steel is as brittle as glass.
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    Senior Member blabbermouth spazola's Avatar
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    Quote Originally Posted by Magpie View Post
    Actually did normalize (I think I did) by leaving the tool in the forge after I turned off the gas, and let it cool down with the forge. I figured that would be a nice slow cooling. perhaps too slow?

    Charlie, what temp do you take your tools to? Maybe my attempts at "auto temper" are not practical.
    I temper my tools in the 450-500 range depending what they are.

    The faster the cooling the better grain refinement works.

    Charlie
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    One thing about forging tools like a hardy cut off tool is to not make them as sharp as many people do. I have been taught that that the only forging tool that needs sharp edges is a set hammer & I can't see a need for a blade smith to use a set hammer. Also a hardy tool that has a thin sharp edge will lose it's temper because of the heat of the metal being cut. In a pinch I made Hardies & cut off tools from mild steel. Heat it up till it isn't magnetic then quench in a mix of one gallon of water with one bottle of Dawn dish washing soap & 1 Lb. of salt. This mix is great for mild steel.DO NOT USE IT ON HIGH CARBON STEEL!!!!!!
    This mix lowers the surface tension of the water & hardens the mild steel a few points. Steel at forging temp is very soft so a slightly hardened steel will cut or forge just fine. That can save you money by not having to buy high carbon steel for all your tools. If it is a high use tool I would probably use a higher carbon steel. Most rebar is a higher carbon steel & I have made many tools from it.

    Slawman;-)
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    First you need some idea of the alloy your using, or enough experience with that alloy to understand how it's going to react. For me, I haven't found anything better than 4140 or 1045 for top or bottom tools. I've HEARD H13 is better in some applications, but since I haven't used it yet I can't comment.

    When you put it in the forge to slow cool you basically annealed it. To normalize bring up to critical temp, which should be about 50 deg.F hotter than non magnetic, let air cool. Some people cool completely to room temp, others to a black heat. Either way works as your not trying to get grain refinement for a blade. Do this three times, each time at a slightly lower heat, third time take it out before it looses it's magnetism. Then if you want to soften it for machining work, bring it back up to a dull red, say about 1200-1400 deg and let slow cool in the forge or heated wood ash or vermiculite. This may be necessary as some steel will air harden. This should get your grain size down and make it easier to file or drill. Afterward quench and auto temper if you want, but I prefer to heat one section and let the colors run, or put in an oven. I make most of my hammers and fullers from 1045 and use a heated drift to transfer heat for the tempering and just watch the oxide colors. Of course 1045 is basically heat to critical, dunk in water and draw to a straw color, more complex and higher carbon steel will require more complex heat treats.

    This is an overview, there's lots more or less you can do. I make hot punches out of 4140, H13 would likely be better but I've got 4140 on hand, and quench and temper even though the very end will lose temper due to the heat of what's being punched. The first hammer eye punch I made I forged from L6 and did a full anneal on it in the oven, first time I used it the eye bent while hammering on it. It needed a little more hardness than dead soft to function correctly, even if the very edge got soft the main body would have been stiff enough not to deform. Part of this could have been achieved by simply heating in the forge and air cooling as the L6 I've got is air hardening. Same thing with 5160 and other high chrome steels, though for maximum hardness they will need an oil quench.

    Hope this helps
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