Subject: Re: need help tempering a spring

From: [email-masked]
Date: Sun, 30 Jun 1996 05:52:23 GMT

[email-masked] (Charles L. Rowe) wrote:

>         I have to duplicate a small helical compression spring.
>      So far, I have formed it to the proper shape, but how
>      do I temper it?  I have the usual home shop equipment
>      at my disposal - a propane torch and some quenching oil 8*) 
>       

There are many ways to answer this question.  There is a lot of open
territory since you have not specified what steel you used or much of
any thing else.  

Assuming that you have a high carbon steel, you should heat the steel
until it cannot be easily picked up by an electro-magnet.  This is
sometimes referred to cherry red heat, but it is much harder to
determine where cherry red is than it is to detect loss of magnetic
properties.  Be quick about this, because with a propane torch, you
will not eliminate oxygen and will start to cause black scale on the
wire.  

When the steel becomes non-magnetic, it has changed crystal structure
to one that is similar to 304 SS (non-magnetic stainless).  Make sure
that the whole piece looks the same color.  At this point you are now
ready to quench the steel.  I generally use water for this, but with
some steels that is too violent a quench.  The chart below lists
quench from least to most severe,

air		Least Severe
hot oil
oil
water
brine		
cold brine	Most Severe

There are any number of other solutions that you could quench in, but
water is one of the easiest to use.  If the quench is too severe, the
steel may fracture or shatter during quenching.  Test it first.  

After the quenching, we are now ready for tempering.  The steel is
very delicate after quenching, and can break like glass.  Tempering
lowers the peak hardness but adds toughness that is very important
with steel.  While the temperature is a little low, a common household
oven can temper the spring at >500F.  Higher temperatures are better.
The general range is 600F to 900F.  There are other ways to temper.

-  Observing the color of a polished section of the metal.
-  or  Drawing the part out of the quench bath before completely
chilling the part.
-  or  Placing the quenched spring in flaming oil ( >800 F).  

These last techniques are not easy to master on large parts or with
thin sections.  Nothing beats experience here.  If you have lots of
the metal, by all means, experiment.  If you have one piece and cannot
easily duplicate it, have a professional help you.  

J M Stuart

Engineer / Inventor / Patentee

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From: [email-masked] (Charles L. Rowe)
Date: 1 Jul 1996 10:05:34 -0400

Thanks for the well detailed response.  The material I'm using came from
    MSC and they don't specify the exact steel type, they call it oil-
    tempered round spring wire, there's no other data on the pack .
   ( It's on p. 1088 of the current catalog)
	
                 Got 6 dozen pieces, lots to practice on!
					Charlie

---

From: [email-masked] (Steve Rayner)
Date: Wed, 26 Jun 1996 08:43:00 GMT

First, heat it red hot and allow to cool.  Then heat to red heat again & 
quench.  Then:

(1) Bury it in brass filings in a tin lid or whatever is handy.  Put a 
clean piece of the same material on top of the filings.  Heat underneath
until the piece on top turns a nice " clockspring " blue.  Then tip the lot
into some water.

(2) No brass filings?  Do this instead:
Suspend the spring by a piece of wire in the middle of a small pot of 
olive oil. It should be pure olive oil.  Heat to desired temperature and 
hold long enough to saturate the spring ( With heat ).  Olive oil boils at
600 F at sea level.  For a harder temper, use a thermometer that reads to 
600F or a bit higher, and consult Machinerys for the temp for the steel 
you have.  Some deep fat thermometers sold for the restaurant trade will 
work for this. I have an ancient pyrometer that reads to 900F, which was 
intended for this sort of thing.

In a previous article, [email-masked] (Charles L. Rowe) says:

>       						thanks,

-- 
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     MY SECRET IS OIL OF HARLEY DAVIDSON !      Steve Rayner
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