I love to read this old stuff. I hope this is not out of place.
Years ago I worked for this guy who's grandfather was a Blacksmith in the mid 1800's. Before he died, his son and my ex boss learned quite a bit.
He had a big selection of Hardies and other tools, and a old forge. He ran this business renting Jack Hammers. The bits too costly to replace were reshaped and re hardened.
My job was such I never did this, but I watched his old Brother in Law do it all the time. Later they used a Rose Bud Torch for heat. I saw many things tempered, even screw drivers and chisels.
Any how I watched this process, something like this.
He heated the bits until white hot,
He stopped and looked at it about long enough to let out his breath.
Stuck it in oil for about 1.5 seconds,
and then in a bucket of water for about same time.
This procedure varied in time depending the size of bit or tool, I even say special bits hardened with liquid nitrogen.
I remember customers saying how his re shaped bits worked better than new.
