-
The BladeForums.com 2024 Traditional Knife is available! Price is $250 ea (shipped within CONUS).
Order here: https://www.bladeforums.com/help/2024-traditional/
how hard is hard?
- Thread starter ipm
- Start date
- Joined
- Nov 26, 2007
- Messages
- 49
When it just wont let you roll over and fall back asleep.
- Joined
- Jul 30, 2006
- Messages
- 44,418
First, you have to remember that a hardness measurement is only good to ±1. So a 57HRC and a 58HRC measured at different times on the same machine or on different machines may actually be the same hardness.
In everyday use there has to be a couple of points difference before I notice anything.
A 58 (57-59) and a 59 (58-60) is not noticeable IMO. But a 56 (55-57) and a 59 (58-60)? I can notice the difference in that. This assumes the same alloy, or at least the same Carbon level.
At the same time, as you say, alloy does have an impact. A 1% carbon alloy at 58 will outperform a 0.75% carbon at 59. At least it did in my side by side manila rope cutting tests. Carbon is by far the most important factor in differences between alloys. Other differences come into play if two alloys have approximately the same carbon content.
Trying to assign hardness or carbon content as the dominant factor? I don't think it is that simple, but I don't have enough data yet to have an legitimate opinion.
In everyday use there has to be a couple of points difference before I notice anything.
A 58 (57-59) and a 59 (58-60) is not noticeable IMO. But a 56 (55-57) and a 59 (58-60)? I can notice the difference in that. This assumes the same alloy, or at least the same Carbon level.
At the same time, as you say, alloy does have an impact. A 1% carbon alloy at 58 will outperform a 0.75% carbon at 59. At least it did in my side by side manila rope cutting tests. Carbon is by far the most important factor in differences between alloys. Other differences come into play if two alloys have approximately the same carbon content.
Trying to assign hardness or carbon content as the dominant factor? I don't think it is that simple, but I don't have enough data yet to have an legitimate opinion.
- Joined
- Oct 8, 1998
- Messages
- 5,403
I think this is a good point.
Not that you should not ask the question, but that you should constantly ask the question, to make sure that you have the best understanding possible.
Another factor is Carbide Hardness (since the carbides are very hard, in a matrix of softer iron) which is defined by alloy. Which is why you see so much use of Vanadium in the new steels, as the vanadium carbide is the hardest carbide that can be formed.
But, on the opposite side, I say that there is more practical application to sharpening than steel. Because, regardless of the steel, if you like the knife, and can sharpen it, conveniently, then it does not matter if it lags a bit, if it is not the absolute hardest and best edge-holding steel out there...
When I was on the retail side, whenever someone asked me about the 'super' steels, I made sure to ask how well they sharpened. And that is not just because I am so good at it, because I view myself a novice who can't take the training wheels off.
Marion
- Joined
- Oct 2, 2006
- Messages
- 1,746
It depends on what you're cutting, and your application demands. The higher your demands for that shaving sharp edge, and the less abrasive the material, the more hardness is key. The rockwell hardness scale is near-logarithmic, so say 60 rc is a whole lot harder than 30 rc. There is a big difference in tensile strength.
1 point rc is 20% increased abrasive wear resistance. In terms of edge retention, it is that 20% plus resistance to rolling. So can 4 points difference in rc double the edge retention until the edge no longer shaves? I've found it does. The type of steel alloy plays only a minor part if you stop measuring once the edge no longer shaves, as only a few carbides would come into play. The difference is a steel like 1095 continues dulling while CPM M4 would continue to hold that edge for a long, long time. In actual use I do notice the M4 cutting for significantly longer, but if I cut boxes until shaving ability is lost, the difference between these two are not that big.
Last edited:
- Joined
- Mar 3, 2006
- Messages
- 7,132
I agree 100% with that opinion. Practical application is all too often forgotten in the quest for 'super steel'. Many would shun Buck's 420HC, or 440C or even 154CM, in their quest for the 'Holy Grail' of steel. As for me, I believe that each steel has it's own personality that the individual user must discover.
- Joined
- May 21, 2000
- Messages
- 6,284
I seem to be able to tell a difference. I have D2 blades @ 58RC and some @ 61RC. The latter seems to hold a better edge, and it takes a bit longer to sharpen. I don't pry with my knives, so I'll always prefer a higher hardness.
- Joined
- Apr 10, 2000
- Messages
- 3,794
In my experience, 1 pt made a significant experience.
I wrote about that in details, still unfinished though - "]Knife hardness importance
Anyway, long story short, I've used 2 different 710HSSRs as my edc knives for several years. I assumed they were 60-62HRC as speced and never bothered with probable diffs. Both blades started out with 30 deg total angle, done with edge pro...
Few years later I ended up with one knife at 40+ deg total angle, another with the same 30.
RC testing showed thicker edged knife was ~59HRC and thinner edged one was 60HRC. Testing was done on 2 different testers, and both showed 59 for that thick edged blade.
Also, on the accuracy of the RC testers. I don't have one, but when I was researching RC testers (wanted to buy one) some of them were speced as low as 0.1RC accurate. So, it's not always +- 1HRC.
- Joined
- Jul 23, 2008
- Messages
- 1,160
LOL :thumbup:
Seriously - hardness on it's own doesn't mean that much. Blade shape & profile, edge angle, geometry and blade grind all affect how a knife performs on different tasks and materials. For many tasks a less hard but tougher knife will be better, which is why many knives are in the "utility" 56-59 RC range rather than 64+.
Then there's all the issues surrounding steel composition and heat treatment that affect carbide grain size and makeup with the associated hardness/toughness, edge retention, rolling, chipping & sharpening.
It's all too easy to become a steel snob but unless you know that all the other paramaters are optimised, focussing just on hardness or type of steel used won't give all the answers. The best criteria is feedback on a knife's performance by actual users.
- Joined
- Aug 2, 2006
- Messages
- 2,809
Blades are measured (usually) on the Rockwell "C" scale.
It is not linear.
The difference goes up very steeply as you get to the higher numbers.
The diference between 40 and 50 is not as great as the difference between 55 and 60. The higher the "C" numbers, the greater the difference in hardness that a small increase makes.
It is not linear.
The difference goes up very steeply as you get to the higher numbers.
The diference between 40 and 50 is not as great as the difference between 55 and 60. The higher the "C" numbers, the greater the difference in hardness that a small increase makes.
- Joined
- Mar 3, 2006
- Messages
- 7,132
Well said, Antonio. :thumbup:
- Joined
- Jan 4, 1999
- Messages
- 3,000
It's important to realize that knife blades are all within about 10 points of each other on the C scale. Below around RC 54 they become too soft to hold an edge for a meaningful period of time. Above around RC 64 they become too brittle to be practical for many applications. It is true that the scale is logarithmic and the changes from one RC unit to the next become greater with higher numbers. But the overall range of hardness is not as severe as some people want you to think. While the difference between a blade at RC 54 and one at RC 64 is meaningful and obvious, the single digit progressions aren't so important. You wouldn't notice the difference between, say, RC57 and RC58 even if you could produce blades that hit those exact numbers consistently. Most RC numbers are provided in a range and the differences in hardness within the range aren't really meaningful.
- Joined
- Nov 1, 2000
- Messages
- 28,365
Too rich to pass up...
I guess my Mission Ti folder would be college math class. My Reese Weiland proto in CPM3V @63 RC would be Viagra
I guess my Mission Ti folder would be college math class. My Reese Weiland proto in CPM3V @63 RC would be Viagra
