Thread: Common Rockwell

I am just wondering if anyone knows what the usual hardness of razors are on the Rockwell scale.
Also, is there a difference in solingen to sheffield?

Samuel,

I suspect most would be in the range 55 - 65 Rockwell C, though there are probably many that are not !

Also as a general note, the edge area tends to be harder than the spine.

Have fun !

Best regards

Russ

Yes its quite a variation. Really depends on the individual razor. There can be a difference even in Sheffield to Sheffield let alone to Solingen.

From www.customshaving.com , in a description of Tim Harner's custom razors:

The blade is heat treated in a computer controlled Evenheat kiln and triple tempered for a final hardness of 62-63 HRC.

And for a TI (fancy alloy!):

are TI blades made of better steel than DOVO? - The Shave Den

Made from the best Steel available today, this numbered razor and box commemorates the new forging dies and new Carbonsong C135 Carbon Steel from Thiers France. The new Carbonsong steel has a carbon content previously unequaled resulting in a Rockwell hardness of 64-65, and delivering a superior edge and a beautiful mirror finish.

That thread (quoting the TI hardness) also claims that the TI edges are right at the verge of brittleness.

For comparison (I'm a newbie):

Lee Valley claims its laminated Japanese chisels measure 65-66 Rc. Lee Valley "O1" (low-chromium steel) plane blades measure 58-60 Rc.

It would be interesting to get some real measurements of both old Sheffield and Solingen blades, from someone who didn't mind putting a small indentation into one of each.

Charles

Originally Posted by cpcohen1945

It would be interesting to get some real measurements of both old Sheffield and Solingen blades, from someone who didn't mind putting a small indentation into one of each.

Josh Earl started a project where he got people to send him junk blades for testing. I'm not sure if it was ever completed. http://straightrazorpalace.com/forge...s-project.html

In that thread, Robert Williams (papabull) mentions having tested some: http://straightrazorpalace.com/209892-post5.html

Originally Posted by cpcohen1945

It would be interesting to get some real measurements of both old Sheffield and Solingen blades, from someone who didn't mind putting a small indentation into one of each.

Maybe one of the custom makers might chime in here.
I maybe wrong but I think you can only test a razor before it is fully ground as the final edge geometry is too thin to support the test. You can test at the tang but that does not give you an accurate representation of the edge hardness.

Maybe you could test a thick old wedge but I doubt a full hollow would cope.

Originally Posted by PhatMan

Samuel,

I suspect most would be in the range 55 - 65 Rockwell C, though there are probably many that are not !

Also as a general note, the edge area tends to be harder than the spine.

Have fun !

Best regards

Russ

wow! that is a huge variance. I wonder which companies border on the 65, because European steel (leastwise kitchen knives) hit about 56 or so Rockwell.
Does anyone know how they would treat the edge to get it harder than the spine?

Only a WAG but the edge being thinner maybe cools quicker in the quench thus harder ?

Originally Posted by onimaru55

Maybe one of the custom makers might chime in here.
I maybe wrong but I think you can only test a razor before it is fully ground as the final edge geometry is too thin to support the test. You can test at the tang but that does not give you an accurate representation of the edge hardness.

Maybe you could test a thick old wedge but I doubt a full hollow would cope.

The hardest part is supporting the piece to be tested. That hollow radius does not lay flat on a test block and the pressure of the diamond indenter can snap hardened steel really easy. I do test the edges when I'm doing heat treatment, but those tend to run about 20 thousandths of an inch thick. If that's hard enough, it will be hard enough for the edge. I have some blocks cut with a negative radius to completely support the piece. There's no point in me breaking something another fellow worked hard to grind.

On a through hardening steel, the edge and the tang will be the same hardness generally. Only the low hardenability steels will have a harder edge than spine using typical "get it hot and quench the whole thing" routines for heat treatment.

You can manipulate a differential hardness by changing the routine some. Only quenching the edge, using a clay coating and so on to delay the cooling of the spine. Those methods will have a hard edge and softer spine.

Something to bear in mind. Do not get too hung up on Rockwell ratings alone unless you are comparing the same batch of the same steel. Different batches of the same steel can have slightly different characteristics and thus performance varies and heat treating needs to be adjusted to optimise this. The top custom blade makers "tweak" their heat treating whenever they begin using a new batch of steel. The old steels created in pours suffered from this variance a lot. The modern powder metallurgy steels such as CPM and Damasteel/RWL34, have overcome this to a large degree and provide a consistent grain structure and alloy mix.
Then there is the fact that different steel alloys at the same Rockwell hardness react totally differently. One blade at 56C could outcut a different alloy at 58C due to the alloy content and carbide structures.
Not meant to be more confusing, but thought another perspective may help explain the differences in performance between brands, and even different razors of the same brand.
Regards