Here is the way I do a tumbler made from 1144 "StressProof".Once the tumbler IS shaped,install it in the lock and function test it.If it works as it should.take it out and heat it to a bright orange and quench in oil.My quench is some very old oi drained from Diesel motors from a long gone city bus company*.Use a magnet and get it out and clean and polish it,all surfaces including the 2 notches.Using a Bernzomatic I draw it to a straw color and let it air cool.This material has proven,at least to me that it works well for this application and is easy to use because it machines like 12L14 or Ledloy.
*This old oil was given to e by George Killen in 1977 shortly before he passed away.He was a gunsmith and WW1 veteran.I have maybe a
coffee can 3/4 full now.Let us know how this works for you.As I said,my locks are spread out across Germany and other parts of Europe and nothing reported so far.
Bob Roller