Blacksmiths' method to Harden and Temper a Spring.

On vacation lately I've gotten to work with some other Blacksmiths.  One of them is Eric Schatzel, a smith of no small skill at traditional work.  One recent project he did was to harden and temper a spring using traditional Blacksmithing methods of heating in the forge and oil quenching.

This is an existing spring that was tempered too soft.  First it was carefully heated to non-magnetic in the coal fire and then quenched in oil.  That is vegetable oil.

Then it was degreased and carefully heated to draw a "Robin's egg blue" spring temper.  I've also heard a Southern smith call this "Possum ear blue"!  In any case it is probably around 630 degrees to impart a good spring temper.

Next a spring vice is used to re-install it.

The spring is now in place.  Light oil is added everywhere it touches other steel to prevent it from binding on a burr.  By the time the oil evaporates it will have worn in.

There it is!