A difference of 175 degrees would have been a huge difference in the annealing furnace, and would have altered the steel to a degree noticeable by the human eye.
Yeah–I think the difference would be noticeable to trained eyes–steel temperature/color charts clearly indicate a difference of 100°F can be be seen. In any case, what happened to this die is outside the norm–I wish I could go back in time and see how it was done! 😀 As a look back, I found this excerpt from a 1924 book on annealing; I would guess similar practices were in place in 1890:
“high-carbon [tool] steel should be annealed at between 1400 degrees and 1500 degrees F. This temperature should be maintained just long enough to heat the entire piece evenly throughout. It is essential, when annealing, to exclude the air as completely as possible while the steel is hot, to prevent the outside of the steel from becoming oxidized. After annealing, it should be allowed to cool at a rate slow enough to prevent any hardening.”
I imagine this also applies to annealing dies at this time–heating up to ~ 1500°F, then a slow cooling–and done after every hubbing. It sounds time-consuming, doesn’t it? I have no idea how cool the dies were when they were hubbed, so my thermal expansion theory is purely speculative. Maybe the doubling is due to pressure changes while hubbing? Whatever the cause, the stepping is interesting enough to photograph in detail. 😀
- This reply was modified 2 years, 9 months ago by DVCollector.