I have been experimenting with spring making for awhile. (mostly flat springs) Just thought I'd pass a few things along. The trickiest part for me was always getting the right temper after hardening. I broke a number of springs along the way by not getting them to the right temp which leaves them brittle. Getting the hardening and tempering colors/temperatures just right is the most important thing. Study a color/temperature chart and remember the order of color change. Heat very slowly moving the torch around. For large springs an Oxy acetylene torch works great. Don't get too close. Hopefully you will have an existing spring to copy. Make a sketch of the spring with all dimensions and try to make the new spring exact to it as you can. Filing in the details will take some time. The picture below is a mainspring that I just finished for an 1894 Marlin. I have been using an old 1/8th inch thick circular saw blade for spring stock. I cut 1/2 wide strips using an abrasive saw blade or cutting torch.
The old UK gunsmith's technique for tempering springs was "burning off".. Having hardened the spring in tempering oil, the spring was then heated up again to the point where the oil coating the spring would remain burning. The burning spring was then left to burn out, and then tested.
Traditionally sperm oil was used to temper springs, however cooking oil seems to do the same job.. and leaves the workshop smelling like a greasy spoon cafe!
That said, I tend to rely more on one of those IR thermometers these days
By the way.. I find one of these really useful for making coil springs...
PM
