I'd add that the initial annealing (where all the stresses are relieved)
needs to be undertaken over a longer period of time ... the ideal method is
to heat the spring steel in a small furnace to red heat for a long time ...
and then let the entire furnace cool very slowly. The absence of air would
be great, but it is not a big issue except that the surface will discolor as
it oxidizes. Hobbyist knife makers use coffee cans with a large hole in the
side for a propane torch and filled with dry sand to act as the heat
absorbing medium so they can get that very slow cool once the blade has
"soaked" at red heat for 30 minutes.
For the hardening phase, you can use oil or water to quench from bright red
heat ... I prefer oil. I'd suggest repeating this step two times.
Before tempering, clean the thing so it shines like a new pin, but don't use
any cleaning techniques that will get the spring too hot ... light use of
wire wheel is fine! Then heat with the spring resting in a dry sand
container in such a way that you can clearly see the colors change as it
slowly heats up. The colors will go from very light straw to dark blue (and
if you keep going, to a nice cherry red ... then you are back at step one
above) fairly quickly. It is a little tricky to heat something that is
quite long so it at a uniform color along its length!
I'd suggest a light/medium blue temper for the first try for a spring.
Light straw is still pretty hard (that's where I stop for cutting edges of
cold chisels).
**************************************
Tony Gordon
72 TR6
**************************************
----- Original Message -----
From: "Randall" <tr3driver@ca.rr.com>
To: <triumphs@autox.team.net>
Sent: Wednesday, May 07, 2008 5:19 PM
Subject: Re: [TR] 1972 TR6 Seat Bolster Springs - Imagine My Frustration...
>> I commenced
>> copying the springs by using a torch to heat the spring
>> steel. It seems to be working, but I question how long they
>> will last, having been heated. I am running out of spring
>> steel and need to locate more. Am I on the right track or
>> completely off the rails here?
>
> If you've heated them enough to bend, and then let them cool on their own;
> there's a very good chance you've ruined the 'spring' temper.
>
> As I recall, the 'book' method for springs is to first completely anneal
> them to equalize stresses introduced during forming (which generally
> requires heating to cherry red then let cool slowly in an oxygen-free
> environment); then reheat to red and quench in oil (not water). Then a
> third tempering step is required, with lower heat and quenching again in
> oil. The temperature in the final step is more critical (but I don't
> recall
> the color offhand, maybe something like "light straw").
>
> Easier IMO to cold-form them; or easier yet to find a stock spring you can
> cut to length.
>
> Randall
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