Bought a portable HRC tester. Some interesting results

[ChrisinHove]

Interesting thread!

So I learned today that the Leeb test measures the rebound of a dynamic probe by electronically measuring it’s rebound velocity and Rockwell the indentation of a probe from an increasing, static force.

Why should one be better than the other for knife steel?

Why not measure the indentation from a dynamic probe (as used in some concrete screed testing)?

[Deadboxhero]

Does mass effect the rebound of an object?

Does HRC testing also need that consideration?

Do the calibration blocks for each test method highlight these differences?

If I'm getting strange readings with my Leeb tester Is it because of the steel or perhaps there's some special considerations due to the physics of how that test works?

Important questions that may shine some light on the subject.

Interesting thread!

So I learned today that the Leeb test measures the rebound of a dynamic probe by electronically measuring it’s rebound velocity and Rockwell the indentation of a probe from an increasing, static force.

Why should one be better than the other for knife steel?

Why not measure the indentation from a dynamic probe (as used in some concrete screed testing)?

[jasong™]

Recently grabbed one of those electronic portable HRC testers. I don't know how accurate these things are compared to the expensive benchtop diamond tipped testers, but thought it would be fun to mess with at least. Saw this style tester on the CBRx youtube channel but haven't really seen anyone else using them and got curious.

Got some interesting results to say the least and thought I'd share. Take everything with a grain of salt, as again not sure how accurate these are. HRC numbers shown are the average of 5 pokes on the tang area near the pivot if I could, sometimes on the primary bevel, or on the ricasso.

This is awesome, thanks for providing this!!

[RustyIron]

Well, regular, non-geek folks looking for HRC data aren't going to understand the nuances and they are going to take anything they see with a number dead serious regardless of the accuracy or the "why" behind best practices.

You are surely correct. Maybe that's why Spyderco doesn't publish their hardness targets for their blades--I can only speculate. If you told me that mystery metal you're working on tests out at RC63, I wouldn't really know if that's good or bad.

All I can speak about is my own experience. In the areas where I'm pretty good, I started measuring stuff without fully understanding. Then I figured stuff out and become marginally competent. Nowadays, on those rare occasions where I'm teaching someone, I let them watch as I take measurements, and I'll give a quick overview as I go. I know they won't fully understand, but they'll have somewhat of a foundation to build upon. If someone calls me with a question and I ask them about some measurement, and they haven't even done that, then I write them off as ill-prepared to have the conversation.

If we dare risk overstepping the shiny footprint rule, in this day and age, everyone watches a Tik-Tok and considers themselves a virologist. Justin Kruger and David Dunning had something to say about this, and it absolutely applies to what you said about amateur hardness testers. Thanks for helping to educate us regular folks about knifeology.

[jasong™]

I think I’d rather have imperfect results as oppose to no results at all.

I'm with you. These are likely to be directionally accurate.

I heard an adage once: Don't let perfect get in the way of good enough.

That said, I dump a lot of money into calipers, because I like them to be suuuper accurate, so I also get wanting your HRC testing to be exact. Still, I appreciate the effort put into this, and it's fun for me as a spectator to this thread to see the numbers.

[Larrin]

I think I’d rather have imperfect results as oppose to no results at all.

I'm with you. These are likely to be directionally accurate.

I heard an adage once: Don't let perfect get in the way of good enough.

That said, I dump a lot of money into calipers, because I like them to be suuuper accurate, so I also get wanting your HRC testing to be exact. Still, I appreciate the effort put into this, and it's fun for me as a spectator to this thread to see the numbers.

But they may not be directionally accurate. It’s supposed to be used with high mass objects so it could be the size of the knife would have a large effect on the result. If your values are variable enough that changes are random or unexpected factors lead to different results that would indeed be worse than nothing.

[jasong™]

But they may not be directionally accurate.

You could very likely be correct there. I'm not putting much stock in these numbers, nor writing them down anywhere. I think at best they're perhaps accurate (somewhat?) relative to this set of testing. For instance, I see his test of M4 is reading harder than S30V for example. That rings true to me.

[Wallach]

But they may not be directionally accurate. It’s supposed to be used with high mass objects so it could be the size of the knife would have a large effect on the result. If your values are variable enough that changes are random or unexpected factors lead to different results that would indeed be worse than nothing.

I agree, but I also think this is why it would be useful to run both tests on the exact same blades.

[jasong™]

If your values are variable enough that changes are random or unexpected factors lead to different results that would indeed be worse than nothing.

And just in case there's any doubt, I'm not going to argue with you on this point. I think you may be the foremost expert (that I know of) on this topic. I defer to you generally on knife steels :)

[Flash]

I understand accuracy is key but does the method in which this hardness tester obtains the results make it completely invalid and the results to be taken with a large pinch of salt in this context?

Or would the results have at least a small amount of credence, even if the test isn’t the industry standard way to obtain them?

[Deadboxhero]

It could be a reason among many.

Rockwell hardness is not a universal measurement even between even two HRC testers.

"65 HRC is 65 HRC buddy"

Not quite.


Some HRC testers folks have are not calibrated properly to agree with other testers.



Here we can see a simplified illustration that does a good job highlighting common errors which also happens to correlate with shooting. The one I circled in "blue" is the most difficult one to detect because it's not intuitive and runs rampant especially in the social media knife community.

Good precision, but poor accuracy.


"My hardness tester is perfect, No way pal, I'm getting 63.0, 63.3, 63.1, the readings are super tight, no way it's my tester bro"

Certified Test Block Avg: 65.2rc
Error: ~2.0rc

Nah, that tester is invalid, gotta go back and clean, fix, replace or adjust something.

Yes, we have precision, but low accuracy. This is not useful for sharing results with others and making sweeping claims about steel hardness on particular product lines etc.

Especially if the difference between good and bad is 1.0 HRC for some reason.


It can be easy to diagnose a lack of precision.

"Yikes, my readings are 62.2, 65.1, 58.7"


But accuracy is tricky and not well explained in the instruction manual with hardness testers which is simply not needed for intended customer which provides on job training for specialized personnel.

For example Brad at Peter's Heat Treatment only allows a handful of people he has trained to use the hardness testers. Not everyone on the floor can use it even though operating a hardness tester is very simple. Well, it made a difference in accuracy so that's why they do it.


My observation has been accuracy is still quite elusive in the social media knife world and is at the mercy of the operator, machine and most importantly certified test blocks and how to use them.



When I was working with Spyderco on the CPM 15V heat treatment the first thing we did was confirm the hardness between our HRC testing to see if our hardness results agreed which they did along with the readings on the certified calibration test blocks.


Otherwise, it would have been rather confusing if the same sample created different readings due to differences in testing machines and testing when trying to dial things in and rule things out.

Well, regular, non-geek folks looking for HRC data aren't going to understand the nuances and they are going to take anything they see with a number dead serious regardless of the accuracy or the "why" behind best practices.

You are surely correct. Maybe that's why Spyderco doesn't publish their hardness targets for their blades--I can only speculate. If you told me that mystery metal you're working on tests out at RC63, I wouldn't really know if that's good or bad.

All I can speak about is my own experience. In the areas where I'm pretty good, I started measuring stuff without fully understanding. Then I figured stuff out and become marginally competent. Nowadays, on those rare occasions where I'm teaching someone, I let them watch as I take measurements, and I'll give a quick overview as I go. I know they won't fully understand, but they'll have somewhat of a foundation to build upon. If someone calls me with a question and I ask them about some measurement, and they haven't even done that, then I write them off as ill-prepared to have the conversation.

If we dare risk overstepping the shiny footprint rule, in this day and age, everyone watches a Tik-Tok and considers themselves a virologist. Justin Kruger and David Dunning had something to say about this, and it absolutely applies to what you said about amateur hardness testers. Thanks for helping to educate us regular folks about knifeology.

[Wandering_About]

But they may not be directionally accurate. It’s supposed to be used with high mass objects so it could be the size of the knife would have a large effect on the result. If your values are variable enough that changes are random or unexpected factors lead to different results that would indeed be worse than nothing.

I agree, but I also think this is why it would be useful to run both tests on the exact same blades.

Much more useful to just use a proper testing device for Rockwell hardness.

[Fastidiotus]

This was the kind of nerdy thread my brain needed today

[Wallach]

But they may not be directionally accurate. It’s supposed to be used with high mass objects so it could be the size of the knife would have a large effect on the result. If your values are variable enough that changes are random or unexpected factors lead to different results that would indeed be worse than nothing.

I agree, but I also think this is why it would be useful to run both tests on the exact same blades.

Much more useful to just use a proper testing device for Rockwell hardness.

...sure, and if those were also like $200 USD and the size of a small phone book everyone would just do that, and instead we'd be having a discussion on who's results are actually accurate. But that isn't what is happening, or will continue to happen.

[Wandering_About]

But they may not be directionally accurate. It’s supposed to be used with high mass objects so it could be the size of the knife would have a large effect on the result. If your values are variable enough that changes are random or unexpected factors lead to different results that would indeed be worse than nothing.

I agree, but I also think this is why it would be useful to run both tests on the exact same blades.

Much more useful to just use a proper testing device for Rockwell hardness.

...sure, and if those were also like $200 USD and the size of a small phone book everyone would just do that, and instead we'd be having a discussion on who's results are actually accurate. But that isn't what is happening, or will continue to happen.

Far better to get the information out there that these testers out there are not giving accurate results, as much as it's possible. Good knowledge depends on good data.

It's a learning moment for us. I'm curious why this particular tester came to market when the ASTM standard gives great caution against correlating Leeb hardness to other scales. There must be a purpose for it?

In any case here is the ASTM manual for Leeb hardness testing. It's an interesting read: https://cdn.standards.iteh.ai/samples/1 ... 56M-22.pdf

Edit to add: I'm not going to guarantee this freebie is the most up to date or full Leeb standard... but still useful for us to learn more about the test.

[Wallach]

I mean, even in the excerpt DBH posted before from this manual posted:

"All such conversions are, at best, approximations
and therefore conversions should be avoided except for special
cases where a reliable basis for the approximate conversion and
the accuracy of the conversion has been obtained by comparison testing."

Doesn't sound that unreasonable to me.

[Evil D]

Even if the numbers your gadget spits out don't correspond with other hardness scales, or they aren't particularly useful in knife making, who cares?

I kinda feel like you listed the important reasons why anyone would care. If this isn't the right tool for the job, then the only thing you get from this info is being able to see a number that shows one steel/knife measures higher than the next, but any of us that know anything about production HRC numbers already know that K390 is harder than S30V. I'm all for having fun but if the information you get is potentially damaging to the real factual numbers then that's a problem because hardness is already a hot topic lately and any kind of false information is just making it worse.

You can't even fart these days without it being taken out of context, and right this very second these pictures are already available on a Google search where someone will only see a picture of a steel next to a number and they'll unknowingly share that incorrect number as the factual hardness.

[Flash]

I’m always happy to learn more about the subject, so the results obtained by the portable tester are interesting if nothing else.

I think the way forward now is for an independent who has access to a proper industry recognised hardness tester and test the knives that way.
What better way to conclusively lay any mis information to rest than with precise and accurate results obtained by a precise and accurate tester?

[Steeltoez83]

²

This is the portable tester I use. I bought it to compliment my cut testing shenanigans. The spirit of my testing is more backyard bro science. For me hrc testing is just an added bonus after the knife has gone thru performance evaluation. Focusing too much on HRC numbers is just paralysis by analysis for regular customers. Knife makers and manufacturers may need to invest in stationary equipment, several calibrated hardness blocks, the indenter itself etc. But they are selling a product and need better accuracy.

[sal]

Hey SteelToez,

How well does that portable work? How accurate is it? what is it called and where can I get one?

thanx,

sal