As always oversimplified answers are rarely accurate and such is the case with Rockwell. There are those who will indeed feel that HRC is the definitive indicator of a knife and there are those who will reject it as some of that new fangled technical hooey, but it is just not that simple. A good blade is a combination of many factors, heat treatment, steel selection, geometry, mass distribution or balance, ergonomics, etc... Rockwell is merely an indicator of one factor- the penetrative strength of the steel, or what we see as penetrative hardness. This factor is very useful in checking our heat treatment process, but says little about the rest of the knife. It is sort of like that old parable of the three blind men with an elephant; assuming you have the entire story just from Rockwell hardness is not a wise approach as it is only one piece of the puzzle and only with a few other pieces can you get any idea of what the big picture really is.

For example- you harden your 1084 blade in the forge and get a 66HRC as quenched hardness. This sounds great, but enlarged grain increases hardenability, so you may have nailed the quench beautifully or you could have made a terrible blade with enlarged grains, only by looking at other pieces of the puzzle besides Rockwell will you know. Another example would be a decent Rockwell but a horrible carbide condition. Proper carbide condition is critical to edge stability, among other factors, but Rockwell can't read carbides,only the larger matrix, to check the carbides you need metallography or a micro-hardness test.

To make matters worse are the vast majority of makers who improperly test with Rockwell. I cannot count the number of times I have had a maker point to single dimple and proudly proclaim the HRC. Rockwell is only good to roughly one point in accuracy and really needs to be averaged from several readings to be useful. I always take at lest five readings and average them, this not only increases accuracy it also give me a picture of the homogeneity of my heat treatment based upon the deviation spread (I am happy to say is rarely exceeds one point). Also Rockwell cannot accurately be taken in any surface that is not flat, parallel and properly finished to 300X-400X. To be honest there are many analytical tests and methods that are often cited as proof of quality by knifemakers who really do not have a full understanding of them. After having done many of them I can tell you that it is no where near as simple as many folks think. But Rockwell is about the easiest and straight forward of the bunch.

I can tell you that Rockwell is invaluable to me in checking my heat treatment procedures, and my life gets very complicated and annoying when I can't use Rockwell. A couple weeks ago I did some consulting for some folks who needed to check a new steel they were using, the HRC numbers were off, but we had no idea why as they were just HRC numbers with no story to them. So I cross sectioned a sample and mounted it up for the metallograph, where we saw the structures responsible for the Rockwell and I was then able to tell them what to change in their heat treatment. The HRC numbers only told me that something wasn't quite right, but I needed other tools to find out what it was.

I don't even own an tester, but I do use my RC chisels to check hardness at a couple of points in my process. I use those readings as an indicator of whether or not my heat treatment did what it should have and as Kevin said I also use them to check the evenness of my hardening/tempering. In those senses I find the readings extremely useful, but I wouldn't ever use those numbers as a selling point, even in a well heat treated blade proper final hardness is interdependent with edge geometry intended use size and a hundred other factors.

MP

Interesting point Matt, I have certainly done a good deal more Rc testing than most, I have filled several notebooks with numbers and had to finally resort to spreadsheets and databases, each and every one of my knives has a documented record of multiple readings, and yet I have never bothered to include an HRC number on the final description for the sale of the piece. If a customer asks, I will tell them the numbers, but I have never found it to be particularly useful, or even that interesting, as a selling point. I guess people just assume that I have something as basic as HRC worked out already.

Another point that could have been added in my last post is the question of what folks know what to do with the numbers if they have them. I often hear numbers for a given alloy that is way out the optimal range for that alloys properties, e.g. 58HRC for small blade made from a high strength abrasion resistant alloy. Folks can get into trouble by merely chasing numbers without an overall plan.

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Interesting point Matt, I have certainly done a good deal more Rc testing than most, I have filled several notebooks with numbers and had to finally resort to spreadsheets and databases, each and every one of my knives has a documented record of multiple readings, and yet I have never bothered to include an HRC number on the final description for the sale of the piece. If a customer asks, I will tell them the numbers, but I have never found it to be particularly useful, or even that interesting, as a selling point. I guess people just assume that I have something as basic as HRC worked out already.

Another point that could have been added in my last post is the question of what folks know what to do with the numbers if they have them. I often hear numbers for a given alloy that is way out the optimal range for that alloys properties, e.g. 58HRC for small blade made from a high strength abrasion resistant alloy. Folks can get into trouble by merely chasing numbers without an overall plan.

Exactly!! I comes down to the customer not being educated to what the numbers really represent! I may use the numbers from the book as a rough estimate when working with a new steel but I figure the final heat treat through testing the blade! only then do I have a heat treat schedule that I can test using rockwell Numbers, and then it is only to ensure that I didn't screw anything up!

I think a part of this comes from the "knife designers" that have come about over the last few years, as well as the many knife makers that send out for heat treating, these guys need to spec out the hardening so they started to obsess about RC numbers (being the only thing they could really call for) and that became a selling point for them I have see this listed in knife publications when doing reviews as well.I guess it would make some sense in a production knife but we as bladesmiths control heat and as such have a far greater deg of control over the heat treating process than production knives or even a lot of knifemakers it they are not doing there own heat treating... Sadly as an advertising tactic it is so common I am even seeing it show up in the Warzibad adverts these days .. you know the beautiful Damascus hunting knife 56-58RC with horn handle only $75!!" guys.

Hmmm, you bring up a point I had not initially seen, the significance of Rc numbers to those who farm out their heat treatment. Indeed to these folks those numbers would be significant since having the heat treatment entirely out of their hands it is the only parameter they have to work with, in both a target goal for the treater as well as an indicator of the results. To those folks the Rc number is all they have to communicate to the customer about the heat treatment, and they have to rely on the expertise of their heat treater to ensure that all the other factors line up with the Rockwell. I hadn't initially seen this because is it so alien to my existence, where I have complete personal knowledge of every aspect of the heat treatment process.

Going back to Mareko's question about selling points and pricing, it may be helpful to consider the customers' perspective, especially a newer customer who's doing some comparison shopping. We can talk all day long in here about the merits of RC testing because we're bladesmiths, but most buyers don't have the same understanding of ferrous metallurgy as we do.

Think about it this way: when you're shopping for a new car, you consider things like horsepower, fuel efficiency (mpg), acceleration (0-60), torque (lb-ft), etc. You browse through a few car magazines and look at the comparative tables listing these same specs side by side; you also see them listed in every brochure and website you will find. As a prospective buyer you like these things because they are objective, quantifiable, and verifiable. You may not be an engineer, and none of these data points will tell you how well the car actually drives and handles because there are a thousand other variables that enter into the equation, but you still want to know how much horsepower she has and how fast she goes from 0-60.

Knife buyers often go through a similar exercise. They inform themselves about their available choices and compare whatever specs they can find. When they look at the websites and various other marketing materials published by well known knife manufacturers like Buck, Cold Steel or Ontario, they will very often see RC hardness listed among all the other major specs, and may come to believe this is as important as the torque from a hemi. Once they graduate from factory knives to custom knives, they may still maintain some of these habits and wish to know the RC hardness of your knife, even though it won't fully tell them how well the knife will actually perform.

I don't know if listing the RC hardness of your knives will make them sell faster or command higher prices, but if asked about it by a prospective customer you may use the opportunity to explain your heat treatment regimen and perhaps educate them a bit about what you consider important about your steel selection, blade geometry, and heat treatment. I would say most customers would appreciate the lesson, and may come away from the conversation with an even deeper appreciation for what you do.

I know I'm late to the party but would like to throw my perspective in as a maker who doesn't own a Rockwell tester. I do have access to a facility with a tester that is maintained and calibrated on a regular basis. Living on the edge of the sub-modern World(NS Canada), it would be very costly for me to hunt down a Wilson bench top tester and have it shipped. It would also be expensive, time consuming and probably not even feasible for me to test every one of my blades at another facility. I have to make due with my current situation. I use Rockwell testing of control "coupons" to calibrate my heat treat process for each of the given steels I work with and regular maintenance/calibration of my heat treating equipment to make sure everything is consistent.

I was recently challenged by another maker who stated that without Rc testing every blade that leaves your shop, you have no right to claim quality control. This was on a public forum and I was a bit upset until it became clear that this maker was testing his knives at the ricasso with a Chinese knock-off of an Ames handheld tester.

The relevance to this thread is that one of his selling features is the little dimple next to his maker's mark. That how you know!