Thread: How Hard Are The Vintage Blades

Well, sadly, you cannot test on the tang/shank. Due to the nature of the immersing the blanks into the cooling liquid, the tang is not effectively quenched...

Nenad

Yesterday was the best day to find another something to do...

Out of pure ignorance I will say somewhere
around 60. A good middle ground for
baby bear - not too hard and not too soft.

But then baby bear doesn't shave....



Terry

Originally Posted by urleebird

A very good point, Nenad. I'm wondering, though, if razors were all processed the same. If they were quenched quickly, there may not be that much difference in the numbers. Since it won't matter if these blades are broken, maybe Mike could test in both areas... blade and tang.

All this reference material in one spot... how cool is that?

Whoo hoo...

Would it matter if the tang/shank was hardened? If not,
I suppose a lot could depend on the person doing the
work on that particular day. Just a thought.


Terry

The tang/shank needn't be hardened. With the simple steels that are used, differential heat treating is possible. What's important is the hardness and grain size in the cutting edge.

I was wondering when hardness testing first became commonplace in manufacturing processes, because until that occurred I would expect the hardness to vary over a wide range since evaluation of the hardening/tempering process would be solely based on a craftsman's gut feel.

I spent some google time, but didn't exactly find what I wanted. I did run across a document [here] titled "Introduction to Hardness Testing". In the section "Hardness Testing Theory" I found the following statements:

• Early methods generally consisted of scratching. Scratch hardness testing consists of penetration of the material surface by a testing point and bears a close resemblance to the indentation hardness test. One of the earliest forms of scratch testing goes back to Reaumur in 1722. His scale of testing consisted of a scratching bar, which increased in hardness from one end to the other. The degree of hardness was determined by the position on the bar that the metal being tested would scratch.
• In 1822, the Mohs scale of hardness was introduced for minerals and measures the relative hardness of ten minerals.
• In the late 19th century, more attention was paid to hardness and its measurement. Johann A. Brinell, a Swedish engineer, presented a paper to the Swedish Society of Technologists describing his ball test. This rapidly became known as the Brinell test and became universally used in the metalworking industry.
• Because of the limitations imposed by the Brinell method and increased engineering requirements, several investigators intensified their efforts toward devising other indenters, principally those made from diamond, to accommodate the testing of fully hardened steels. In 1919, the Rockwell test was introduced. It has become, by far, the most popular hardness test in use today, mainly because it overcomes the limitations of the Brinell test. The inventor, Stanley P. Rockwell, a Hartford, Connecticut, heat treater, used the test for process control in heat treating.

So, if I had to guess I'd think that the metallurgy gurus in Solingen most likely wouldn't have gotten the quality control of hardness very accurate until the early 1900's... perhaps as late as 1920. As I understand the process, until hardness testers using diamonds became available accuracy was compromised at the values we expect to see for razor steel.

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?

Great thread. My guess is probably in the range of 60.

The whole discussion on metal and analysis reminds me of an article I read a long while back in Fine Woodworking where they compared chisels from various manufactures. All were modern and from various manufactures. They did a complete set of functional tests ( hone, cut wood, etc. ) and looked at things like edge wear etc. Also they cut them up and looked at things with an electron microscope to check out grain, etc. Hardness was also in the analysis. I think at the end of the day, the steel quality was the overriding differentiator.

This sound about right when thinking about razors, especially from the older types. Good steel makes for a good razor. What make for good steel? I suppose volumns have been written on the subject.

It's true to an extent. You could give me a blank made of best steel ever but you wouldn't want to shave with it after I put it through the grinder. However a good metalworker will also tend to use good steel so it it's a chicken and the egg sort of a question.

This has me thinking. In times the best steel was identified by where it came from. Was this because the had better raw materials there or better know how or perhaps both. ( Again a chicken edd thing. )

Given our technology today, I wonder how much of the quality is due to raw materials and how much is due to technology. I hear the Paki razors are crap because they have inferior steel. Is this because of inferior technology or raw materials or both?

Originally Posted by urleebird

I'm wondering, though, if razors were all processed the same. If they were quenched quickly, there may not be that much difference in the numbers.

On the DOVO video the guy is dipping the rack with the razors in oil. They are fixed to the rack in the tang area. Even if the dip was quick enough, I still suspect the rack will prevent the heat to dissipate fast enough from the tang, and will even hold some of the heat through the whole process... And if the razors are dipped one by one, the tang might get the dip after the edge is quenched completely (usually several times, both oil and water), so measuring hardness there would make little sense...

Nenad