Thread: How Hard Are The Vintage Blades

Maybe the best place to measure hardness would be the bevel on the spine??

Nenad

Originally Posted by azjoe

I was wondering ... (clipped)...Could this explain why a small sample of razors (2-5) would yield a wide variety of hardness numbers, particularly if some were forged before and some after hardness testing became commonplace?

An excellent recitation of the history involved. There could be a lot of variation even in one factory. Example: the quench bath starts out cold in the morning and after a session of multiple razor blades is much warmer by the end of the heat treatment session. There should be measurable differences in hardness between the morning and noon and so on. If the company controls the temperature of the quench bath (marquenching) then the blades should be uniform within a degree of uncertainty. Between different factories using differing processes, all bets are off.

I can block up the flat parts on my Rc machine so as to isolate that from the curvature and get a pretty good reading on the hardest part of the edge. I might be able to set up a curved block and get a range of readings from edge to spine. Then a series from toe to heel and the tang.

Whether the tang is hardened depends on a couple things. The hardenability of the steel, e.g. some steels will not harden all the way through and the section thickness and speed of quench determines the end point. The depth of quenching also, e.g., if the tang is not immersed it may not get to full hardness. And, the tempering cycle can reduce hardness after heat treatment. There are some exotic but not impossible methods to refine grain that can contribute to hardness or weakness depending on what is done. Without knowing the rituals done inside the factory, i can't comment much.

Forging will align some grain, but realistically, there is nothing magical about a forged vs. ground blade. All steels must be forged to some shape at the mill, so a non-forged steel really doesn't exist to compare to. The key is in the steel first, and the heat treatment second, with the HT playing a much larger role. A lesser steel heat treated well can hold it's own against the best steel marginally heat treated.

I think I got all the questions.