Thank you so much!

Quote Originally Posted by Mike Blue View Post
I'm with Charlie about tempering. Only one cycle is necessary and O-1 tops out for hardness at about 400F. I'd recommend finding and studying TTT diagrams like this one: (down this page a bit...) Carpenter O1
Many of the makers wrote about the two cycle of tempering. Why, if one cycle is necessary?

Carpenter O1

Why are there two numbers in Effect of Tempering Temperature on Hardness of O1 / Rockwell C hardnes column? For example 60/63 or 60/62.

Hardening

"Without preheating, place the tool right in the hot furnace and let it heat naturally until its color uniformly matches the color of the thermocouple in the furnace. Soak an additional 5 minutes per inch of thickness, then quench in oil. The temperature of the tool should be brought right down to the temperature of the oil in the quench."
Based on this I must leave the razor in the furnace up to 10 minutes or maybe 5 minutes as mentioned Bruno, isn't it?

Quenching time
What is the recommended duration in case of a blade? I usually do between 10-40 sec.

Quote Originally Posted by Mike Blue View Post
One of the variables mentioned by Bruno earlier was the time taken between the heat and the quench. His cooling fin example is accurate. This diagram shows that you have about 2 seconds to miss the nose of the curve to get into the martensite range of transformation. Do not dawdle from the fire to the quench...
I used to be within one second.

I would like Rockwell hardness tester in the future but it is too expensive for me.