RC values: real world relevance

Revolverrodger

Revolverrodger

Joined
Jul 23, 2007
Messages
3,889
Many people scoff at knives with lower RC values and many think that anything under RC 57 is unfit to be a knife...
I have to say that I am starting to wonder what RC values really means in a knife
For example I have an ontario sp50 in 5160 RC53-55 that I have used for years to chop, batton carve and it still remains sharp.
It looks like high RC values are pretty much only usefull for knife testers that spend their time slicing thousands of peices of cardboard
I don't slice cardboard in the outdoors

What is the relevance of high RC to the outdoorsman ?
 
Hardness tests give a quick and easy check with production knives .For the user it's a guide to performance . The actual performance depends on many things. Edge geometry, very important and so is grinding [heat ] damage to that edge.How long does that edge remain ?
 
High RC is relevant because the steel (barring other variables) will hold an edge longer than a softer RC. I like choppers to have a softer RC to avoid more dramatic damage, but closer to the 58 range than the 55 range for sure. Its not the biggest deal in the world, but it does help in the real world. Grind and geometry play a bigger part in the real world.
 
Revolverrodger said:
Many people scoff at knives with lower RC values and many think that anything under RC 57 is unfit to be a knife...
I have to say that I am starting to wonder what RC values really means in a knife
For example I have an ontario sp50 in 5160 RC53-55 that I have used for years to chop, batton carve and it still remains sharp.
It looks like high RC values are pretty much only usefull for knife testers that spend their time slicing thousands of peices of cardboard
I don't slice cardboard in the outdoors

What is the relevance of high RC to the outdoorsman ?
Click to expand...

A similar question was brought up on the Ontario knife sub forum concerning their HRC numbers. Below is a response from Toooj (Paul Tsujimoto, Director of Engineering, Ontario Knife Company).

From the Ask Toooj" thread post # 8.
Toooj said:
I went out into the factory and took readings on both Gen II Spec Plus blades and some Bushcraft blades (both are 5160). They were all 57-58HRc after temper. This is perfectly acceptable for 5160 and for larger blades that will take a beating.
I understand that our catalog lists our 5160 knives at 53-55HRc and our 1095 knives at 53-58HRc. I don't know who came up with those specs but I'm thinking they will be changed in the future. We should be able to list a closer Hardness Spec than that.
As a general rule of thumb; larger blades that will be used as choppers, batoners, etc. will be tempered a couple of Hardness points lower than blades that need edge holding and sharpness. 5160 is an extremely tough steel but it can also be hardened to fairly high Hardness. There is only approx. 0.60% Carbon so that after saturation into the steel matrix, there isn't a lot of free carbon remaining to form carbides...not there are a lot of other alloys in the 5160 chemistry to form carbides. Interestingly enough, not having large carbide strings also allows the edge to not chip out as much. It is typically the large carbides that chunk out at the edge.
Hope this helps.

Best Regards,

Paul Tsujimoto
Director of Engineering
Ontario Knife Company
Click to expand...
 
Higher RC, as a general rule, increases resistance to plastic deformation like rolling, bending or denting, but at the cost of toughness, increasing the risk of chipping or cracking. But with modern steels that have toughness to spare like 3V you can still have plenty of toughness to avoid breakage, but gain enough hardness to gain much greater edge retention and avoid rolled edges and dents.
 
I have a L6 kitchen knife done by a hobbyist that is very hard. I have a William Henry in ZDP that is about Rc 65. Both hold an edge for a super long time. The kitchen knife is routinely abused by my family and I sharpen it no more than once a year with a little touch up on sandpaper. I really have not had to sharpen the William Henry.

What is the relevance of high RC to the outdoorsman ?

To me high hardness means holds an edge. Both knives are not used to chop, just to cut. If I was an outdoorsman, I would think not needing a sharpening setup in the woods would be a good thing. If I had to process multiple animals at a hunt, edge holding would be important. Even Buck's cheapest 420HC is run at Rc 58.
 
I will appreciate high hardness (like 62 Hrc) on a pocket knife or a kitchen knife because they are not to be exposed to what could be called abuse. I will be pleased with the longer lasting sharpness. However, on tools likely to be submitted to impact (machete, axe, cleaver), my experience is that (relatively) low carbon steel at low hardness (57 Hrc and below) performs beautifully. The balance of edge holding and ease of repair is just about spot on. Come and go, you will repair / resharpen a lot anyway... so, it's better if the edge has not chipped away. Soft steel rules in that application.
 
You can have two blades with the same RC rating, and they will perform very differently. It depends on how they were heat treated. Edge geo will play a big roll too, especially in the outdoors if you are chopping, or want a thin knife to slice.
 
Do I understand right that cpm m4 dominates the bladesport competitions? If so, does anyone know what hardness these competition blades are?
 
buckfynn said:
A similar question was brought up on the Ontario knife sub forum concerning their HRC numbers. Below is a response from Toooj (Paul Tsujimoto, Director of Engineering, Ontario Knife Company).

From the Ask Toooj" thread post # 8.
Click to expand...

Thanks for the update concerning OKC true RC values
 
buckfynn said:
A similar question was brought up on the Ontario knife sub forum concerning their HRC numbers. Below is a response from Toooj (Paul Tsujimoto, Director of Engineering, Ontario Knife Company).

From the Ask Toooj" thread post # 8.
Click to expand...

Originally Posted by Toooj View Post
I went out into the factory and took readings on both Gen II Spec Plus blades and some Bushcraft blades (both are 5160). They were all 57-58HRc after temper. This is perfectly acceptable for 5160 and for larger blades that will take a beating.
I understand that our catalog lists our 5160 knives at 53-55HRc and our 1095 knives at 53-58HRc. I don't know who came up with those specs but I'm thinking they will be changed in the future. We should be able to list a closer Hardness Spec than that.
As a general rule of thumb; larger blades that will be used as choppers, batoners, etc. will be tempered a couple of Hardness points lower than blades that need edge holding and sharpness. 5160 is an extremely tough steel but it can also be hardened to fairly high Hardness. There is only approx. 0.60% Carbon so that after saturation into the steel matrix, there isn't a lot of free carbon remaining to form carbides...not there are a lot of other alloys in the 5160 chemistry to form carbides. Interestingly enough, not having large carbide strings also allows the edge to not chip out as much. It is typically the large carbides that chunk out at the edge.
Hope this helps.

Best Regards,

Paul Tsujimoto
Director of Engineering
Ontario Knife Company
Click to expand...

Interesting. So the quoted numbers are not what is really done. The number he stated makes more sense.
 
Hardness is mostly a marketing tool in many instances. In the range of hardness of knives, higher hardness does not mean lower toughness, in many cases. Hardness is more a by product than a goal.
 
jpm2 said:
Do I understand right that cpm m4 dominates the bladesport competitions? If so, does anyone know what hardness these competition blades are?
Click to expand...

I believe they are quite hard. That is because the people doing the cutting are highly experienced and know how to cut/chop without causing too much lateral stress with their movements. Part of the reason production companies run knives a little softer than maximum is to give a little user error leeway.
 
You must log in or register to reply here.
Back
Top