Has it some difference between HRC 58 and 60?

raidops

raidops

Joined
Jun 22, 2006
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Hello
I mean the difference is or isn't enough to feel when we care the blade. Someone says there are certain different feeling when sharpening and using of the two. But I don't feel anything. My knife is fixed HRC 58. Because I use the D2 steel. Our heat-treatment specialist give hia hearty recommendation the best HRC to D2 is HRC 58 to keep endurance. My customers are also interested in the hardness and they are satisfied with their HRC58 stuffs. But somebodys require HRC 60. They seem to be considered the HRC58 to save the cost. Anyway, Is there any difference between the two? Thanks.
 
I would think that there maybe some difference in the edge retention between the two RC's, and you might be able to tell between the two when sharpening on a stone. There will some knowledgeable folks along shortly; it will be interesting to see what some of our resident material experts say about this.


Steve
 
don't most production knives advertise a 2 point window?

Rc hardness 54-56, 58-60, so on
 
I don't have a link but IIRC Bob Dozier posted here that you should be able to get Rc to within half a point. The two point window is just slop.
 
Razorback - Knives said:
D2's peak performance level is at 60/61 rc.
Scott
Click to expand...

Scott is right on the money as usual. Dozier is it the man when it comes to D2, his 60/61 blades are amazing. I haven't tried D2 at 58 so I can't comment on that.
 
If you want to "feel" the difference then take a blade that is HRc 58 and one that is HRc 60/61 and try to file the edge. I have tried to file 154cm at HRc 60, using a new Nicolson or simmons file and it just makes a "zinging" sound and does not remove hardly any metal but at HRc 58 the file will remove metal much easier.

a couple of points on the Rockwell "C" scale makes quite a difference.

FWIW,
Ciao
Ron
:rolleyes:
 
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raidops said:
I mean the difference is or isn't enough to feel when we care the blade.
Click to expand...

Generally it isn't the hardness you are concerned about as much as what happens to the steel at that hardness. Specifically D2 has a compression and wear resistance maximum at a very high hardness :

http://i7.photobucket.com/albums/y269/CliffStamp/steel info/d2_hardness.jpg

and

http://i7.photobucket.com/albums/y269/CliffStamp/steel info/d2_izod.jpg

with an oil quench + cold you can reach 65 HRC which should make for a very fine cutting knife.

-Cliff
 
ras said:
I don't have a link but IIRC Bob Dozier posted here that you should be able to get Rc to within half a point. The two point window is just slop.
Click to expand...
Not quite. The two point range is what you get from batch heat treating. When you have a thousand blades in a bin inside an oven there will be some variation. A little bit of heat difference can mean a big difference in final hardness.
 
Okay, I found link to the Dozier quote and the quote
The D2 blades leave this shop at 60 RC to + a few tenth's. We made several thousand at 62 and found that they would cut all day on tissue and paper but would loose the cutting edge if anything really hard was cut. Most makers give their hardness at 58 t0 60 or 60 t0 62. This is sloppy heat treatment.
Click to expand...
I was close.
 
Well, if you are talking custom knives, then yes, a two point range is sloppy. It doesn't take much to nail down the hardness. Just a set of rockwell files and a few minutes should tell you to the point.

You'd need an actual Rockwell tester to get closer than that.
 
Not to go off topic, RC 58 though 65 has been mentioned in this thread.

Does anyone know the best all around RC for D2?



Now back to the topic.

Steve
 
60-62 Rc is what Crucible says in their write-up, but show heat treats from 55-63. Bob Dozier goes with 60 (see link in previous post).
 
It isn't the hardness which is critical but how it is hardened. D2 has three rough ranges, very low temper of 300F for 62/64 HRC for maximum hardness and wear resistance, moderate at 500F for 58/60 HRC for a combination of properties, and above 950F for 58 and under for optimal toughness. All of these hardness values will be elevated by oil+cold. Most makers run at the intermediate values by default. Mel Sorg used to run at very low tempers, some use the very high ones. You can effect the properties as well by how hot the blade is soaked. In short, don't just look at the hardness.

-Cliff
 
Recommended soak times for D2 are between 30 to 60 minutes depending on temp. I run mine for 55 minutes at approimately 1850. Recommended temps are between 1815 and 1900. I do a 2 hour temper twice at 400 degrees. A new metal file won't touch it. I even wear out fresh belts during clean up. I don't have a rockwell tester but I estimate my blades at the 60/61 hardness range with the data I follow.
Scott
 
Thanks a lot Razorback-Knives! By the way, Is it no problem endurance at the degree HRC 60~61Hardness? My D2 blades were broken like glass at the degree.
 
raidops said:
Thanks a lot Razorback-Knives! By the way, Is it no problem endurance at the degree HRC 60~61Hardness? My D2 blades were broken like glass at the degree.
Click to expand...
If they are made of thin stock, say 1/8" or thinner, yes they will be prone to breakage under heavy lateral stress. Especially if they are thinly ground. Save the heavy duty knifework for thicker blades. 1/8" thick, convex grind have held up fine for me but then again, I'd feel more confident with a 3/16" thick D2 blade for hard use. Ron Hood has a D2 knife I made for him and has used it hard for almost a year. :D
Scott
 
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