PHR-1 vs Ames Hardness testers - any complaints?

matto6 said:
+/- 1.5 = spread of 3 which is somewhat laughable. I suspect they say that just so people can't return the machine saying it's out of spec. I would hope it has much lower variance than that.

ASTM E18-20 is awesome thank you for the pointer. It even has a precision/bias study (Table 4) that tells you what you should expect in terms of (a) expected error when reproducing your own readings ["r_pb"] and (b) expected error when reproducing someone else's readings ["R_pb"].

I also have one of those certifications with my PHR-1 which shows 5 readings and shows it's within 0.5 HRC of the correct number - but how do you know it's real? Unless it's performed by a 3-rd party trained in they can write whatever they want on it. Even if it's not totally fabricated, it's easy to just drop readings that are wonky until you get a few that look nice enough to write down.
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It is a factory "allowance"

The customer has to calibrate it when they set it up anyways.

The regulation plate can be adjusted +/- 5 HRC to fine tune upon setup.

You have to make sure you use multiple hardness blocks at different values so that you are not just "block chasing"

It's good to see you are having some skepticism. This is what fuels a deeper thirst for knowledge rather just asking random questions to random people on a forum.

The fear of uncertainty of measurement in ones own hardness readings shows a deeper level of understanding and humility. It is a reason why those of us that care will only use certified hardness blocks and certified indenters, fine tune the dwells, double check the test forces and do more frequent calibrations and log them to watch how the reproducibility changes over time.

Just like how even the sharpest edge on the longest cutting steel can also wear and dull, critical components of the hardness tester also degrade.

Calibration is like watching how the edge of a knife dulls over time with use and when we need to intervene before problems arise.
 
It's been years since I took statistics, but a +/- .5 Rockwell rating tells me I need to take multiple samples and average them. What is the standard practice with Rockwell samples? How many readings are recommended, and do you throw out the high and the low?
 
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Most blades I get back from HT have 3 HRC test dimples on them, so I do 3 tests and see what the results are.

Mine is an older Wilson 1JR tester and I have to set the dial to match the pointer needle at zero before I test. I find when I am getting the machine ready to have the load applied, which is done manually on mine, if I move the dial to go to zero at the needle placement, sometimes the tester needle itself moves and the test is off. If I leave it and add or subtract the offset from zero instead of moving the dial, it's more accurate. So if I am showing the needle starting point at 1 HRC below the zero, I add 1 HRC to the results. If I show the needle at 2 instead of zero, I take 2 hrc away from the results showing. I can usually get the needle to be within 2 hrc of zero. If it's more than that, I reposition slightly and redo the setup completely. I use a calibration block on mine and also blanks from HT places that I know and trust (Bos and Jarod Todd) that have been HRC tested to make sure I am on with my numbers.
 
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HPD said:
It's been years since I took statistics, but a +/- .5 Rockwell rating tells me I need to take multiple samples and average them. What is the standard practice with Rockwell samples? How many readings are recommended, and do you throw out the high and the low?
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It's 0.5rc in allowed error on +60rc test blocks not the "rating" or tolerance of the block.

A certified block comes with a certificate with actual hardness measurements that are traceable to the NIST standard.

Also, the analog dial has 0.5rc in resolution which is not to be confused with the actual precision of the machine.

Please study the testing standards.
 
DeadboxHero said:
It's 0.5rc in allowed error on +60rc test blocks not the "rating" or tolerance of the block.

A certified block comes with a certificate with actual hardness measurements that are traceable to the NIST standard.

Also, the analog dial has 0.5rc in resolution which is not to be confused with the actual precision of the machine.

Please study the testing standards.
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All I'm asking is how many measurements you're supposed to take of each sample and how to average them, including whether or not to throw out the high and low measurement. There's no need for me to "study the testing standards" at this point, especially considering I don't own a Rockwell tester. I'll give you the benefit of the doubt and assume you didn't understand my question. I appreciate you clarifying that the .5 Rockwell number was not in reference to the precision of the machine (which is what I was assuming).
 
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HPD HPD I take more readings with my Grizzly when I am running coupons and trying to dial in heat treat for a steel. Once I figure out my heat treat I will take a couple readings from a batch to make sure something odd did not happen but for high alloy if you are follow a recipe the results are always repeatable and the same. My AEB-L recipe always produces 61.5 Rc.

If I was ego driven and searching for the elusive "ultra super mega heat treatment" then maybe I would be more concerned with the Rockewell tester to prove myself.

I have yet had to adjust the Grizzly. It came reading accurately with the test pieces and still does after a few years of use.
 
I think you'll be happy with the HR-150A - you've got good test blocks to check it with. There's a good method of calibration paper floating around I wrote up a few yrs back. As I mentioned before, my HR-150A is a good bit more repeatable/accurate than the ±1.5 given on the calibration paper I posted. The image shows with a 62.2 test block the readings were 61.7 and 62.1 (as best I can read the numbers). That's only ±.4 points. That's pretty close to the spread I normally get.
 
Good calibration puts the mind at ease, makes troubleshooting a breeze and keeps the customer pleased.
 
I got my Wilson calibration block in the mail. Holy crap, I'm able to get incredibly consistent readings with the PHR-1.

It seems to be the case that:
1) A good calibration block makes a difference
2) My PHR-1 reads 1.5 low.

Wilson Block [Actual 63]
Measured: 61.5
[61.5 61.5 61.5 61.5 61.5 61.25 61 61.5 62 61.5 61.5 61]
 
matto6 said:
I got my Wilson calibration block in the mail. Holy crap, I'm able to get incredibly consistent readings with the PHR-1.

It seems to be the case that:
1) A good calibration block makes a difference
2) My PHR-1 reads 1.5 low.

Wilson Block [Actual 63]
Measured: 61.5
[61.5 61.5 61.5 61.5 61.5 61.25 61 61.5 62 61.5 61.5 61]
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Hmmm... I was advised on another thread to avoid these, but your testing suggests they might be worth looking at. I was also considering the HR150A. I suppose when you consider all that comes with the HR150A it's a better deal. But...if you're on a budget the PHR-1 could be an option if it's as accurate as your testing indicates, not withstanding some of the drawbacks of portable units discussed by others on this thread.
 
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HPD said:
Hmmm... I was advised on another thread to avoid these, but your testing suggests they might be worth looking at. I was also considering the HR150A. I suppose when you consider all that comes with the HR150A it's a better buy. But...if you're on a budget the PHR-1 could be an option IF it's as accurate as your testing indicates.
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Technically speaking, my measurements were precise but not accurate. My measurements are all consistent, but they are off from the truth by 1.5 (this is what the ASTM E18-20 refers to as the bias.) It's the equivalent of the dart board analogy where your darts are in a tight group, but they're not near the bullseye were where you were aiming.

Lack of precision can be overcome by taking more measurements and averaging.
Lack of accuracy (ie, having bias) can be overcome by measuring the bias and compensating for it (add back in the 1.5 every time).

My HR150A is in a Fedex truck now and I'm looking forward to receiving it. For 3 reasons.

1. The PHR-1 is susceptible to several sources of human-induced noise. You need to (a) turn the dial smoothly without stopping, (b) stop at precisely the right spots when both loading and unloading (b) head in the right place both while turning the knob and reading the result, (c) make sure you're not touching the test block or the arms while taking the reading.

2. The potential for additional sources of human error that I haven't yet identified bothers me. Just because I produced 10 readings in a row tonight that were consistent, it doesn't mean that tomorrow I could produce the same result. If I sit in a different chair and see the dial at a different angle, or turn a bit faster, maybe I'll have a different bias tomorrow? How can I be sure of this unless I calibrate every time I take a new measurement

3. The PHR-1 cannot be calibrated. Mine is off by 1.5 so I need to do math. Bah


But if you (a) are obsessively meticulous about your form, (b) use a quality test block to measure it's bias, (c) are willing to remember that bias and add/subtract it every time you take a measurement for the rest of eternity, it seems to have the potential to be quite consisitent.
 
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DanF said:
If I recall correctly, Willie 71 had and used the portable Ames type successfully in helping perform a lot of testing for the knife making community and on the knives he made?

See how it does for you then decide?
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Oh no!!!! We have to throw out all of those results now.
 
matto6 said:
Technically speaking, my measurements were precise but not accurate. My measurements are all consistent, but they are off from the truth by 1.5 (this is what the ASTM E18-20 refers to as the bias.) It's the equivalent of the dart board analogy where your darts are in a tight group - but they're not where you were aiming.

Lack of precision can be overcome by taking more measurements and averaging.
Lack of accuracy (or having bias) can be overcome by measuring the bias and compensating for it. But this only works if the bias is consistent and never changes.

My HR150A is in a Fedex truck now and I'm looking forward to receiving it. For 3 reasons.

1. The PHR-1 is susceptible to several sources of human-induced noise. You need to (a) turn the dial smoothly without stopping, (b) stop at precisely the right spots when both loading and unloading (b) head in the right place both while turning the knob and reading the result, (c) make sure you're not touching the test block or the arms while taking the reading.

2. The potential for additional sources of human error that I haven't yet identified bothers me. Just because I produced 10 readings in a row tonight that were consistent, it doesn't mean that tomorrow I could produce the same result. If I sit in a different chair and see the dial at a different angle, or turn a bit faster, maybe I'll have a different bias tomorrow? I'm not sure unless I do like a million more experiments.

3. The PHR-1 cannot be calibrated. Mine is off by 1.5 so I need to do math. Bah


But if you (a) are obsessively meticulous about your form, (b) use a quality test block to measure it's bias, (c) are willing to remember that bias and add/subtract it every time you take a measurement for the rest of eternity, it seems to have the potential to be quite consisitent.
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Excellent. Thanks for this response. And thanks for reminding me about the difference between precision and accuracy. I'll probably get the HR150A.
 
M matto6
There doesn't appear to be a way to adjust the tester without sending it back to the manufacturer (ElectroArc)

While you can use a correction factor, according to the ASTM E18-20 If a tester doesn't measure within 0.5rc on the +60rc blocks. The tester is unusable and It has to be serviced.

Why?

It's because the underlying issue can be the tester is not performing the true Rockwell test with the specific KGF required or with the specific geometry required from the indenter, or even not measuring the depth accurately (2μm=1rc)

How does that happen?
Everything wears out and goes out of tolerance with use and abuse.

Correction factors are for errors within 0.5rc on +60rc blocks and 1.0rc on softer side of the Rockwell scale.

What is interesting is it may not be 1.5rc low throughout the entire Rockwell scale (20rc-70rc)

So, it would not be accurate to slap a "1.5rc" correction on the entire scale without confirming on other blocks with different hardnesses. Not to mention there simply being a fundamental error in the testing machine, a hidden underlying reason for the error which needs to be addressed when the error is that large.


Electric arc (The company that purchased Ames back in 1975) Requires you to send the tester in once a year to calibrate it and keep the tester accurate. However, if the unit serial number shows it is too old. They cannot calibrate it.

gF08uBu.png


Seems like that would add up pretty quick, there's also a probably a big reason why they're being sold so cheap used on eBay is that they can no longer be serviced.

With a HR150A, calibration can be done in house by adjusting dwells, replacing indenters, adjusting the regulation plate and testing on three certified hardness blocks (not the blocks it comes with) at different hardness ranges to confirm calibration.

That will work at least until in the far future when the knife edges on the main components eventually wear out and it can no longer hold a hardness tolerance (everything eventually wears out)




Portable hardness testing is really a specialized tool for reaching areas you cannot get to with a traditional benchtop tester and you pay for it with more calibration cost and inherently less accuracy but it's a necessary evil for some applications.
rHGY2HF.jpeg


That's a cool ad that shows a special use case for using a portable tester to measure clutch plates, the electronic version is interesting and would add more R&R, however, the problem with electrical components is they also eventually break and with no hope for repair when the main board dies and the company no longer has a components on the shelf to replace it.

Lastly, you'll like this video about metrology, It doesn't just apply to hardness testing. Metrology is the study of measurement. Even if all of us tried to take the most accurate measurement of a length of a material, we may all get something different if we try to measure as closely as possible.
 
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Wow, thanks for the info.

And yes, excellent correction.. My PHR-1's bias at 63 HRC is +1.5. Its bias at other hardnesses is unknown. There's no reason to believe it is a consistent additive shift across all hardnesses.
 
matto6 said:
Wow, thanks for the info.

And yes, excellent correction.. My PHR-1's bias at 63 HRC is +1.5. Its bias at other hardnesses is unknown. There's no reason to believe it is a consistent additive shift across all hardnesses.
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Since you're mostly interested in measurements in the range of 60 or so. I'd say you're good to go. Looking forward to your reviews when you get the HR150A
 
HPD said:
Oh no!!!! We have to throw out all of those results now.
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MODERATOR -
I deleted the last post because I felt it was in response to a mistaken interpretation of the intent of the quote above. I am pretty sure that HPD meant is in humor.

Warren's tests were by someone who understood what he was doing and using the tools he had as precisely as possible.
 
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Stacy E. Apelt - Bladesmith said:
MODERATOR -
I deleted the last post because I felt it was in response to a mistaken interpretation of the intent of the quote above. I am pretty sure that HPD meant is in humor.

Warren's tests were by someone who understood what he was doing and using the tools he had as precisely as possible.
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Yes, I was joking. Sarcasm doesn't always translate well over the Internet.
 
matto6 said:
Wow, thanks for the info.

And yes, excellent correction.. My PHR-1's bias at 63 HRC is +1.5. Its bias at other hardnesses is unknown. There's no reason to believe it is a consistent additive shift across all hardnesses.
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Talked to Ames today, I was curious why they couldn't recalibrate copies and older models past a certain serial number, Well the answer was very interesting.


"The PHR-1 tester is a Chinese copy of our Ames model 1 tester. If that is the tester you have we can not calibrate it due to the low quality of the indicator that is used.

As these testers are used the frames actually bend slightly. This fatigue can build up over years of use and cause the tester to become unreliable due to repeatability issues.

If the tester is reading off that means the frame has fatigued some and require the indicator to be recalibrated to the new stresses in the frame."

That seems to highlight the underlying reason for the 1.5rc error/bias and why a mathematic correction factor will not suffice when the error/bias is too large (>0.5rc)
 
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