Quote:
It seems to me that once tempered, the steel is no longer at max hardness. If I begin at that point and temper for a second, and possibly a third time, am I not reducing the hardness each time, and thereby arriving at a steel that is too soft to produce a good edge? Quote
Think of the steel as paint, made up of a number of different colors.( austenite, cementite, martensite etc.
If they are not mixed well you see each individual color. ( first temper)
If you want them to combine to make a new color you have to mix well.( repeat tempering)
I've been tring to understand this also.
Hope this isn't over simplified or off base.
Please feel free to correct if I'm to far off base.