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?
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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:
And for a TI (fancy alloy!):Quote:
The blade is heat treated in a computer controlled Evenheat kiln and triple tempered for a final hardness of 62-63 HRC.
are TI blades made of better steel than DOVO? - The Shave Den
That thread (quoting the TI hardness) also claims that the TI edges are right at the verge of brittleness.Quote:
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.
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
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.htmlQuote:
Originally Posted by cpcohen1945
In that thread, Robert Williams (papabull) mentions having tested some: http://straightrazorpalace.com/209892-post5.html
Maybe one of the custom makers might chime in here.Quote:
Originally Posted by cpcohen1945
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.
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.Quote:
Originally Posted by PhatMan
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 ?
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. :)Quote:
Originally Posted by onimaru55
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, :confused:but thought another perspective may help explain the differences in performance between brands, and even different razors of the same brand.
Regards
maybe Tim Harner is a brother :)
i would bet that most blafdes fall in the 57-60 range and the new guys and custom makers are running a bit harder then that (think around 59-62)
Samuel,
After soaking at the right temperature, the edge is quenched first, then the rest of the razor is slowly lowered into the quenching medium - this leaves the edge harder than the spine.
There are some videos of Mastro Livi doing this on the 'InterWeb'.
For commercial, bulk production, razors, I do not know if they are treated the same; possibly/probably not due to the cost etc.
Dovo & TI used to use (still do ?) molten lead for their heat treating process, so I suppose practicality would dictate that they would quench the entire razor at once.
Have fun !
Best regards
Russ
Imo, blades at 65 HRc are really not fun.
Even at 62 HRc, they can be a bitch to get a bevel on and get them shaveready. 65 would be many times worse. So all in all I think 62 should be the maximum hardness for a blade. Going harder than that is imo pointless and counter productive.
A very good refining point in the discussion. And without ever having been to my shop, you correctly identify one of my practices with a new batch of steel. :) :beer2:Quote:
Originally Posted by Adam G.
It wasn't until about the 1940's when industrial steels (big bucket stuff, the lab fellows were a little further ahead) were even concerned with chemistry. Before then, it was a matter of following more ritual than anything. Now chemistry drives everything.
Sorry, I couldn't resist jumping in.
Don't be overly concerned with Rockwell hardness readings. The Rockwell C scale is only good for plus or minus one point anyway. That is by the specifications of the test. A blade that is advertised as 60HRC could be anywhere from 59HRC to 61HRC. A good machine, with a good operator can keep things to within 1/2 a point. But even then, things will vary on a given machine on a day to day basis. Testing against a known standard is required with every batch of tests.
Rockewell C specs. call for a minimum thickness of 0.030". So testing an edge requires a microhardness tester (Yup, I have one). You will see those values as Knoop or Vickers with the associated weight used for the test. You have to be careful with microhardness readings too. I can pick out individual carbides and get the equivalent of 67HRC every time.
Hardness values only tell you about the steel's ability to resist a dent from a diamond pointer, under a given weight. You can also correlate other things from hardness tests such as tensile and impact strength. On a practical basis, it is most useful for research and checking to see if you botched the heat treat.
For razors, things like abrasion resistance, carbide size, retained austenite, etc... also come in to play when discussing sharpness, edge holding, ease of honing, etc. Hardness is only one of the variables. Hardness is important, but the other stuff is just as important. As an example, a 62HRC blade of 1095 is much easier to hone than a 59HRC blade of 154CM.
Edges may be harder than spines, or not. That depends on the type of steel and the heat treating techniques used.
The best, real test of a razor is to hone it, and shave with it. Lynn's correct again. :)
If you want to jump in to the morass of metallurgy, a good place to start is Metallurgy Fundamentals by D. Brandt - Amazon.com: Metallurgy Fundamentals (9781566375436): Daniel A. Brandt, J.C. Warner, J. C. Warner: Books
Tim Z.
just to clear up a bitQuote:
Originally Posted by cpcohen1945
the site that you got the quote off of was www.classicshaving.com
i am on there as Lloyd R Harner and Tim Zowada is the man that showed me the way.
since it was quoted i thought i should make it right