RC Hardness vs Knife Purpose

[xspook2158]

I have tried to search this before I asked.

I realize that different steels may require a different RC or am I incorrect about that ?

How do we know or find out what is the best RC for a particular usage of a knife ? Is there a guide that we can use?

Examples: Hunting Knives, Filet Knives, Utility Knives, Bowies, Boot Knives, Mil/Tac knives, Skinners.

There are so many different types of knives and uses. How can we find out what type of tempre or hardness is best for the purpose?

Jeff

[Jason Fry]

Hardness is often an opposing factor to durability. What I mean is that if you go really hard, say 63, then you're more likely to chip or break. On the other hand, if you go softer, say 56, your edge retention goes down.

That said, I do my smaller hunting knives and EDC's at 60 or 61. A knife of that size is less likely to be abused, and more likely to need to hold an edge a long time.

[Doug Lester]

I'm not quite sure what you mean by certain steel require a different HRc. The are certain steels that can obtain certain hardness levels better than others; they might not even be capable of obtaining a certain hardness levels as others. Some alloys are designed to retain more toughness at certain working hardness levels or retain more hardness at higher temperatures.

Edge retention is more a factor of wear resistance but that usually increases and decreases directly as the hardness does so that is one of the reasons that hardness measurements is used as an indicator of how well a blade will retain an edge. It is possible for two steels to have the same hardness but different wear resistance when one steel's wear risistance is caused more by carbide formation more that martensite formation.

In general, blades that will for cutting rather than chopping will work "better" with a slightly higher hardness level to increase wear resistance. Blade that are designed for heavy chopping will probably do better with a slightly lower HRc, maybe 56-58. Keep in mind however that blade design also plays a role. A cutting blade can get by with a more acute angle on the bevels, as can be obtained with a hollow grind. A big chopper will need more steel behind the edge. I leave the primary bevel just a little thicker on the edge before I cut the secondary bevel which I use a concave grind for. Hardness is only one factor in blade design. With either the harder, thinner blade or the softer, thicker blade I can still get a hair popping edge. They just won't last the same length of time, all other things being equal.

Doug