Zappa wrote:Wapiti wrote:Basically, you soften the spring by heating it and allowing it to cool in the air,
You then can bend the spring to the profile you wish, to give the hammer more tension.
You then heat it cherry-red, ideally to the point it is no longer magnetic (you can use one of those cheap pocket extendable magnetic pick-up tools,
And then, using long nose pliers, dip it in an old tin can filled with any mineral oil and swish it around.
this has opened a whole new world for me. I have a bunnings MAP torch which i use to unfreeze bolts and anneal copper washers etc. Never thought it'd be powerful enough to tackle med-high carbon steel.
when you say "soften by heating and then bend", do you mean get it to a point where it almost starts going a hint of red, then let it cool down completely. Then attempt to bend? Will it bend or will it spring back to shape?
The rest is pretty straight forward.

It's much easier than you think, and this is my experience and observations in doing it very successfully.
Heat the part with your torch (map gas in the yellow bottles is hotter than LPG in the blue bottles, so just hold the flame back a bit if using map gas, speed is not required, use patience) just to a cherry red all over. If, from looking at the part, make sure at least that the section of a w-spring for example, is definitely heated cherry red. The extremities of the part that aren't doing the work aren't that important, but try and do it uniformly.
Then just turn off the torch and let the part cool in air, as long as it takes.
This will soften the part where it can be bent open a little, or stretched, depends on the part.
There are different viscosities of oil to use, some steels are best water quenched, more confusing info on something you'll never find for your part anyway. Just use some mineral oil, whatever you have.
You can search the internet and get all concerned about temperatures, the changing structure of the steel, but don't even worry about that.
Before trying the part, you'll have to harden it again, or it'll just bend back!
Heat it up again, if you have one of those small magnets you buy to pick up dropped bolts etc, it's convenient and easy to handle. Better still, have a second person do that if it helps. Heat it ideally to the point the magnet won't stick. Familiarise yourself with what that feels like first, when the part is cold.
Dip the part in the oil in your old tin, and swish it around because the heat will vaporise the oil and the part mightn't get uniformly hardened.
Pull it out, and degrease it. Polish it up with some emery cloth do you can see the part change colour in your oven, you're looking for a straw shade of yellow when you temper it. Again, don't fuss over the colour.
Tempering will take the brittleness out of the part, toughen it if you will.
For those who reckon I'm a bit blase in my temperatures and descriptions, I've made, rehardened and reshaped plenty of springs, and fussing over colours, times, descriptions of the changes to the steel haven't made any difference and all have worked perfectly.
Maybe if you are a bit reluctant or a little nervous, that's cool, we all are the first few times. Maybe knock up a similar part from scrap and practice first in your handling, use of gear, how best to hold the part, all of that. Go for it!
Unless you burn the steel with oxy/acet by overdoing it, you can soften and harden a spring over and over.