How to Test your Heat Treat

Casey Brown

Well-Known Member
#1
Outside of a Rockwell Hardness test, what are some good ways to test to see if you got a good heat treat? I know about testing with a file to see if it skates or bites as a simple test. What are some other methods that you use to test your heat treat? I am currently heat treating utilizing my propane forge, and think that I am zeroing in on a good heat treat, but want to verify the quality of my heat treat before I even think about selling a blade to a customer.
 

EdCaffreyMS

Forum Owner - Moderator
#2
Personally, I use the brass rod test on EVERY blade that goes out the door. It's not an indicator of any specific/exact hardness, but rather a test of the correct working hardness for the given steel, with the given edge geometry you've installed.

Don't fall into the mindset of "harder is better"! It's not! What you should shoot for is the correct hardness for the steel you're using, with the geometry you've ground on it.

Personally, I feel way too many knifemakers who only seek high hardness, forget that their clients/customer will eventually have to re-sharpen any blade that is used.... and if a client/customer struggles to, or flat out can't sharpen it because the hardness level is too high......it give the person who made the knife a "black eye".

I was caught up in the "high hardness" thing for a while during my early days, Rc testing nearly everything. After a while it became so predictable that I sold off the Rockwell tester...... it was just sitting in the shop gather dust and rotting. :) What hardness level do I use? For the steels I use, and the geometry I apply, 57-59 is what I choose. I don't demand those exact numbers on everything....various designs/uses dictate.
 

Justin Presson

Well-Known Member
#3
Personally, I use the brass rod test on EVERY blade that goes out the door. It's not an indicator of any specific/exact hardness, but rather a test of the correct working hardness for the given steel, with the given edge geometry you've installed.

Don't fall into the mindset of "harder is better"! It's not! What you should shoot for is the correct hardness for the steel you're using, with the geometry you've ground on it.

Personally, I feel way too many knifemakers who only seek high hardness, forget that their clients/customer will eventually have to re-sharpen any blade that is used.... and if a client/customer struggles to, or flat out can't sharpen it because the hardness level is too high......it give the person who made the knife a "black eye".

I was caught up in the "high hardness" thing for a while during my early days, Rc testing nearly everything. After a while it became so predictable that I sold off the Rockwell tester...... it was just sitting in the shop gather dust and rotting. :) What hardness level do I use? For the steels I use, and the geometry I apply, 57-59 is what I choose. I don't demand those exact numbers on everything....various designs/uses dictate.
Ed do you simply run the edge along the brass rod and see if it returns to straight. I have a small neck knife Im working on and it is aebl super thin and i can run my nail along the unsharpened edge and it kind of wants to defore a little.
 

J. Doyle

Dealer - Purveyor
#4
The brass rod test, while valid in some senses, can be a little misleading too in others. Specifically, if you have to push REALLY hard to get your edge to flex or can't see it flex at all no matter how hard you push, then your edge geometry is likely too thick and the brass rod test won't mean much.

Personally I feel the brass rod test is more valid to a maker that KNOWS FOR CERTAIN their edge geometry is already dialed in.

For a new guy, I'd use a knife of already known decent quality to compare my knife's slicing and cutting capabilities on every day materials.
 

Casey Brown

Well-Known Member
#5
So, that is a good point. I'm definitely still playing with edge geometry. Trying to find out how thin to grind before it's ready for an edge is always kind of a guessing game for me, especially depending on the type of blade I am trying to make. I appreciate all of the feedback though. I haven't actually started trying to sell any of my knives yet, as I want to make sure that everything is "right" before I get a customer. I'm literally on my 21st knife that I have made, but only the second that I have actually done the heat treat on. I was actually thinking about selling this one. I think I got the heat treat figured out, but want to make sure before I let anyone spend money on something that represents me.
 

EdCaffreyMS

Forum Owner - Moderator
#6
John makes a valid point about the edge geometry..... sometime I don't think outside my own "box"...... I strive to create blades with the finest edge geometry possible, and still have the edges hold up well under heavy use. That in itself dictates that I tailor the heat treatment of the given steel to the geometry I apply/grind.

Personally, I would say that if you can't use hand pressure to "flex" and edge over a brass rod, then you need to rethink how "heavy" your making the blade's edge geometry. Just to qualify that statement, I am speaking to those particular steels that are generally used when forging. You can't apply the same logic/standards to stainless steels....they just don't work that way.
 

Andre Grobler

Well-Known Member
#7
i cut with it, i sharpen to a ridiculously low edge angle 7-10dps and then do kitchen work or whatever with a test knife, then I see how it degrades... for everyday / outdoors knives i take a heat treat sample grind it and put a very fine edge and whittle / cut hardwoods and see how the edge lasts... i also see how it behaves under sharpening stones to see if the burr is easily avoided when sharpening and the edge is easily formed at very low angles... then i know the steel is fine, then you can adjust the edge for the application...
 
#8
The brass rod test, while valid in some senses, can be a little misleading too in others. Specifically, if you have to push REALLY hard to get your edge to flex or can't see it flex at all no matter how hard you push, then your edge geometry is likely too thick and the brass rod test won't mean much.

Personally I feel the brass rod test is more valid to a maker that KNOWS FOR CERTAIN their edge geometry is already dialed in.

For a new guy, I'd use a knife of already known decent quality to compare my knife's slicing and cutting capabilities on every day materials.
I am glad to hear you mention this John. The brass rod test is very similar to the ABS bend test in that is it based upon flexing and bending, so is rather vague on what it is really measuring, and thus very open to misinterpretation. If you did the ABS test just enough to flex the blade, but didn’t measure the degrees the handle moved, and the blade neither bent nor broke, how much about the heat treatment would it tell you? How much about the blade geometry and overall thickness would it tell you? This is what must be sorted out when flexing any part of the blade. Truth be told, unless you damage the blade (i.e. bent or cracked) all you have measured is the amount of stiffness due to the material thickness. The heat treatment only determines how the flexing action ends and, to some extent, when. But the “when” is still heavily influenced by the thickness, regardless of the heat treatment, if the steel is thin enough not to generate the required resistance to load to exceed the yield point.

E.g. take a set of feeler gauges, one hard, one dead soft. As you get thinner in the stack there will be less chance of bending or breaking, regardless of the heat treatment, until you can go all the way around in a loop at .001”
 
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