OK this should challenge even the fount of locost knowledge.

One of our Victorian doorlocks has given up the ghost.
Basically there are two spring steel levers inside the lock to activate the catch. These are effectively V shaped with the bottom of the V rounded to fit the pivot. Size about 60mm long i.e. 120 when opened out by 10mm deep.
Have tried cutting down a flex. hacksaw blade but they crack after rounding out the bottom (cherry red heating then quenching in oil).
Question is how much heat/what sort of tempering should I try to ensure they don't crack?
Any other suggestions gratefully received.

Cheers, Pewe

Those old V-springs are often quite a complex shape - fat section at the join of the 2 leaves, thinning towards the end.

You really need some strong spring steel - don't know the carbon content offhand - perhaps some thick clock spring would work. Heat it to cherry-red then allow it to cool slowly (shove it into some dry sand). Bend it to shape (for a severe bend you might have to bend it while it's red-hot) then clean it up nice and shiny. Sit it on a tray with a layer of sand on top, and heat it with a blowtorch from below. Watch the shiny bits - when they get close to turning a blue colour pick the piece up and drop it into a pot of oil.

Hopefully it will be springy...

Afterthought: Do a google search for "making flat springs" - there are lots of american gunsmith videos that illustrate the process.

[Edited on 10/5/10 by David Jenkins]

Try Holt Springs. They supply weird stuff that's very malleable, you bend to the
shape you want then cook at 200c and hey presto you have a springy thing

Thanks guys - never ceases to amaze me how much knowledge there is on this forum and how readily the advice is given.
Cheers, Pewe

quote:

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Originally posted by pewe
Thanks guys - never ceases to amaze me how much knowledge there is on this forum and how readily the advice is given.
Cheers, Pewe

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Perhaps this place could help?

I've made knife back springs from O1 tool steel, you can buy it in all kinds of sizes and thickness from Cromwell tools. Heat it with a blowlamp to cherry red and quench in oil then blowlamp again till the oil on it flares and quench, repeat the last step a couple more times and it makes it springy.

[Edited on 10/5/10 by Peteff]

i used to work for a company that manufactured the spring steel for various applications.

What you want is cold rolled (not annealed) steel, composition is about 0.8% carbon (and almost nothing else). If only they hadn't laid me off i could get you some!
But as nige says, you can form it, coil it, whatever, then heat treat it at 200°C (ish) and voila! a spring!

Aw Grimsdale, you've provided a proper explanation.......and I thought it was witchcraft........spoilsport