On Dec 7, 7:20*pm, "Buerste" wrote:
Months ago, we made some small machine parts from 1" x 1/2" x 2" ground
stock from McMaster. *The instructions to my heat-treater were to make them
"as hard as possible" 58-63R. *They are a big outfit running 24/7 and do a
lot of 0-1. *But, when we got the parts back we tested to 49R.

So, did the steel fail or the heat treater?

The prescription for O1 hardening is to quickly oil-quench; if your
part is complex (thick and thin parts) it might not quench perfectly
uniformly. Can you ask your heat-treater about air-hardening
steel options?