blade hardness

marekz

marekz

Joined
Jun 16, 2008
Messages
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what are the different ways to measure the rockwell scale on a blade. Is there anyway you can do it with a file and be close to accurate? thanks mark
 
I saw a pretty neat post on another knife site before that I'd like to test out some day. Someone said that Wayne Goddard heat treated and rockwell tested squares of his steel of choice at several different hardnesses. They said that he then runs a file along each one and compares it to how a file runs along his blade. The claim is that he can tell within 1 RC how hard a blade is. Don't know how true it is, but I'd be interested in playing with it.
 
Once a file starts to skate across the steel seems it would take a very accute sense of feel. Cap comeing to the meeting in Oct.?
 
i test my hardness with a coarse file and i can tell if i'm close but not exact. my buddy that does the testing said i have been fairly consistent at getting my blades between 63rc and 65rc. i have a blade that i'm going to get tested. just guessing i'm saying i have it around 64rc. i'll have him write down the hardness then take a picture of the knife and post the picture.
 
I don;t have access to a hardness tester, but I use the same 2 steels all of the time and heat treating formulas developed by folks who know what they are doing, so I don't really have problems with hardness. For me, buying a Paragon oven and some Parks #50 made my life much easier as now i have pretty tight control over the process. In a pinch, the brass rod test seems to work pretty well.
 
marekz said:
what are the different ways to measure the Rockwell scale on a blade. Is there anyway you can do it with a file and be close to accurate? thanks mark
Click to expand...

I had been fighting with the same issue marekz. I have a Rockwell tester but found that trying to get an accurate reading on the edge is nearly impossible. Until I recently came up with what I believe to be a pretty good solution I was seriously considering purchasing a set of the hardness test files like A.D. Sharpe referenced.

AcridSaint said:
I saw a pretty neat post on another knife site before that I'd like to test out some day. Someone said that Wayne Goddard heat treated and rockwell tested squares of his steel of choice at several different hardnesses. They said that he then runs a file along each one and compares it to how a file runs along his blade. The claim is that he can tell within 1 RC how hard a blade is. Don't know how true it is, but I'd be interested in playing with it.
Click to expand...

That's nearly the same technique, (and the "solution" ) I've been using for the past couple months. I harden and temper a 3/32" x 1" x 1" pad of the same material, at the same time as the blades. I try (as best I can) to match the quenching of the pad and the blades. So far it's been working pretty good for me and has been an interesting learning experience. Compared to blade bevels the flat & parallel pad is a piece of cake to accurately check on my tester :thumbup:

marekz, if you decide to get a set of the hardness test files please post some feedback on your results using them. I've been curious about them for a while now and have considered it might be a good back-up or "double check" to the pads I'm using now


:)
 
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great info-- i will be looking at purchasing a hardness test file, however, i will be leaving the country from 9/8 till approx 10/30 for an unfortunate family matter. when i get back and after i practice using the files - I will definetly post my experience.--thanks mark
 
By the way Andy, yes I'll be at the next meeting. I saw this earlier but got side tracked and forgot to reply.
 
I guess files are a way of finding out if your hardening worked at all - but I'm convinced a Rockwell tester is worth the money.

I recently had a customer send me a blade he identified as 440C. I hardened and cryoed it and it tested just shy of RHC64! I double tempered at 350 and it was still over 62.

After checking with the customer he said he was pretty sure it was 440C but told me to do what I could to get a reasonable outcome.

I double tempered at 500 and it came in about 59.5. Obviously, this was not 440C - more likely 154cm or equivalent.

I wouldn't have caught this with a file - and the blade may have failed.

I suppose if you are sure of your steel - and have built confidence in your process and your equipment, then occasional testing may serve, but I don't believe there is any reliable substitute for a Rockwell tester.

Rob!
 
I've never used one, but I can tell you that Ray is a super smart guy and if you are willing to put in the effort it'll work for you.
 
i just found out the results on the knife i had rockwell tested. i guessed 64rc after testing the edge with the coarse file i always use. i missed it by 2 points but he had to go higher up on the blade due to the taper. the blade tested at 62rc.
 
So mr. richard J --do you feel comfortable enough to rate one of your blade's rockwell hardness with your system--as far as customer response. I mean how many makers on this forum who sell have there knives tested on a rockwell hardness tester? whats the norm?--mark
 
i have always tested my blades with a file right after heat treat to get an idea if its hard enough or not. if a file cuts in the edge i know its not hard enough and needs to be redone. if it cuts in a little i know its probably below 60rc. last year when i got back into making knives again i had almost every knife rockwell tested to see if i could still judge when to quench. out of all i had tested they were all within what i want except for 1. i am lucky enough to have a friend that has access to a rockwell tester so i could get each and every one tested if i want. i rely on color to tell me when to quench and so far i have been fairly consistent. i cant tell you how many makers have their knives tested since its not something i ask every maker i talk to.
 
I bought a Rockwell tester, but before that I was taking my blades to a local machine shop.

They have a Wilson tester that's worth about $6k... and they'd test my blades for $2 each. That was pretty cheap insurance. :)

Rockwell sure isn't everything... but it's a real good indicator that things went the way they were supposed to during heat-treat.

I was surprised to find out how soft... and also how hard... some of the steels were that I thought were right on the money before I started getting them tested.
 
Nick I think I'll take your advice and find a machine shop who'll do hardness testing for me. I've been pretty subjective with my heat treat; basically just trusting to the manufacturer's HT table to achieve the hardness I'm targeting. I've used the same steel for most of my knives and have had good cutting test results, satisfying brass rod tests and happy customers, but I've never had an objective measurement of the actual hardness of any of my blades.

For what it's worth my testing has been nothing more than running a file over the edge after tempering, cutting pieces of cardboard into tiny strips after a test sharpening and finally still shaving hair. If all that works out I figure it's good and go ahead and finish the knife. But that's always seemed a little too simple-minded to me. I just never thought of taking it somewhere for testing. Maybe if I do that a few times I'll be more comfortable with my shop tests. Good thread, thanks!
 
Jim Batson claimed he could get within a point of being dead on with a file.

However, that is because Jim always used the same file..and he "KNEW" what the exact hardness of that file exactly.

I believe Jim could do it...from testing many blades...over many years.

Experience is a good thing.

But if a guy wants to be able to make claims about the knife he is building and selling...he better "KNOW" what he is claiming is fact not speculation.

Shane
 
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