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Tempering Coil Spring Punches


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#1 Blacksmith Jim

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Posted 25 July 2007 - 05:44 PM

Howdy all,

I have recently starting making a number of tools for myself. Various punches, hand fullers, etc.. I have used old coil springs for the material. I believe I understand the steps involved in heat treating, however I have never done it before, and I do have one question.

I am planning on heating to non magnetic, then quenching in 3 gallons of veggie oil (in a metal container with a metal lid). I'll use some files to test it. I'm assuming I want to temper it to a purple or bronze color on the business end of the tool. So here is my question.. What is the best way to apply heat for tempering? I have read about the one heat method, where you quench only the tool end, and then use the heat from the rest to run the colors down. I might try that, but am not sure it is the best method to start with. If I want to quench it entirely, then apply heat again, should I hold the butt end into the coals? Should I heat some tongs up and hold it with hot hot tongs? Should I heat a pile of sand and stick the butt end into the hot sand?

Also, is it OK that the butt end isn't hard? Won't it mushroom more? Could the tool bend from hitting it too hard if the back end isn't hardened to some degree?

I'm sure experience will be the best teacher for me, but I thought I would solicit some wonderful advice here.

Thanks all!
Forging the world around him. ~ http://sweetthangchocolates.com

#2 BeaverDamForge

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Posted 25 July 2007 - 06:17 PM

I'm a noob to forging but I've seen a demonstration on heat treating. What I'd do is heat just the business end to non-magnetic (or however you judge the heat) and quench it. Then heat the piece from the middle (or the other end if it's short) to run the colors. The tip should just turn the color you want. Do it slowly or you may have to do it again. :)

Good Luck!

#3 Glenn

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Posted 25 July 2007 - 06:50 PM

It seems everything is turning to safety in the recent posts. Tempering the working end to your needs and leaving the struck end soft is the safe way of doing things. This allows you to dress the tool when it mushrooms, rather than dressing the wounds from flying shrapnel when pieces break off.

Temper the metal for the intended use of the tool.

If someone questions your standards, they are not high enough.

Do not build a box, that way you do not have to think outside the box.


#4 Blacksmith Jim

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Posted 25 July 2007 - 07:20 PM

Should the struck end be essentially normalized? If so, then heating from the middle once the whole thing has been hardened seems like a bad idea. In that case heating from the struck end makes more sense to me..

Once the tool has been quenched and hardened, what is the best method to apply heat to it to temper it?
Forging the world around him. ~ http://sweetthangchocolates.com

#5 Glenn

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Posted 25 July 2007 - 07:45 PM

Hardening is making the steel as hard as it can become due to composition chemistry. Tempering is drawing the hardness back to make it a tool that will work for your purpose. (Where is a metallurgist when I need one?)

Take a piece of mild steel and heat the end to A2 or non-magnetic. Now quench the end to freeze the crystalline structure of the metal. This is accomplished by dipping the end into a quench media. Now let the residual heat from the tool flow back to the tip of the tool and watch the "colors" run. Quench again (full quench) when you see the color you want which represents the temperature of the metal. This is where temperature wax sticks, or pyrometers come in handy.

Different metals temper differently and at different temperatures.

Where is a metallurgist when I need one? Oh yes, the Blueprints !!

BP0078 The Metallurgy of Heat Treating



If someone questions your standards, they are not high enough.

Do not build a box, that way you do not have to think outside the box.


#6 Tyler Murch

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Posted 25 July 2007 - 08:57 PM

The working end needs to be hardened, and the striking end needs to be pretty soft; that's as-forged (or if you're a perfectionist, normalized).

Heat only the working end to quench. If you don't want it hard, don't get it hot. So only heat the working end to quench.

Now the way to heat to temper, there are several ways that work. You can hold it above (or outside the mouth) of your forge and let it heat slowly while rotating it. You can heat the striking end with your forge or a torch and let the colors run to the end. Remember that steel heats from the outside-inward. You must heat it very slowly to allow the temperature to be mostly equal inside and out.

The only time I practice the method where you quench the end and let the residual heat run and draw the temper is if it is a water quench, and I would not quench a coil spring in water.

I have the habit to make a hot punch or hot chisel real quick for a quick job and not heat treat it. Many times, being that since it is ALLOY or HC steel it is durable enough for the job without having to be heat treated. In fact, not too long ago I punched and drifted a 7/8" hole through a 1-3/4" thick piece of steel with a single punch/drift made from 1018 mild steel, a simple, yet laborous feat for a lone blacksmith with hand tools only at ANY rate.

#7 J W Bennett

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Posted 25 July 2007 - 09:50 PM

RegionalChaos,
My coil spring punches are forged and then air cooled, Then I heat the whole punch to Non-Magnetic and then quench the business end in oil, being sure to move it back and forth in the oil. I quickly hit the last inch to expose shiny metal with the belt sander(2 steps from the quench tank) or a strip of emery cloth tacked to a piece of wood and draw temper to a dark straw color.Then quench the whole punch. Works well for me.
Chisels I take to a dark blue.

John
I just wish I could forge more time!

#8 BeaverDamForge

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Posted 26 July 2007 - 06:21 AM

Should the struck end be essentially normalized? If so, then heating from the middle once the whole thing has been hardened seems like a bad idea. In that case heating from the struck end makes more sense to me..

Once the tool has been quenched and hardened, what is the best method to apply heat to it to temper it?

I suggested heating from the middle merely to shorten the time it takes for a long punch (the one I made is about 10"). The struck end wouldn't be hardened unless you quenched it somewhere along the way so it shouldn't matter.

Use a low heat for tempering, I think it was said that it only takes 400-650* to run the colors. A propane torch or gas stove is enough. Too much heat, and they'll run too fast, not stopping where you want. The demonstrator I saw (Charles McRaven) told us not to requench as it could harden the parts you don't want hard, but I wonder if the temp is really high enough. He did say you could lay the piece on the anvil to slow the colors.

Good Luck!

#9 Blacksmith Jim

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Posted 26 July 2007 - 11:12 AM

RegionalChaos,
My coil spring punches are forged and then air cooled, Then I heat the whole punch to Non-Magnetic and then quench the business end in oil, being sure to move it back and forth in the oil. I quickly hit the last inch to expose shiny metal with the belt sander(2 steps from the quench tank) or a strip of emery cloth tacked to a piece of wood and draw temper to a dark straw color.Then quench the whole punch. Works well for me.
Chisels I take to a dark blue.

John


John,

This actually seems the easiest method to me I guess. It seems like it would be difficult to hold the piece into the forge for a slow heat, and I don't have a torch yet. But wouldn't quenching the whole piece after you draw the temper harden the end you strike? Have you had a problem with that?

Anyway, I'm sure I just need to go do it already and I'll figure it out. Thanks for all the feed back!
Forging the world around him. ~ http://sweetthangchocolates.com

#10 J W Bennett

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Posted 26 July 2007 - 12:07 PM

No, It hasn't been a problem so far and I have several punches and chisels tempered this way. By the time you draw the temper color you want on the business end the striking end has cooled significantly. perhaps that keeps it from getting hard/brittle.

John
I just wish I could forge more time!

#11 rthibeau

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Posted 26 July 2007 - 07:27 PM

JWB has it right in that if the punch is long enough and you heat the struck end, by the time the heat reaches the business end the other has cooled on it's way to normalized. Quenching the whole thing is the thing to do.
Richard Thibeau, blacksmith and creative metal recycler www.dancingfrogforge.com




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