Anyone ever have a hardness tester go nuts on you?

My Rockwell tester kept, indoors in a clean place away from the shop with central heating and cooling. ISO recommends testing at 23°C +/- 5° C
Thermostat reads 23.3° C / 74°F

I was just using it earlier today, read everything fine.

Used the $30 indenter trended 1rc low.

Switched back.

Everything back to normal.

Same temperature, same day, same tester, same operator, same procedure.



.






Keith Nix said:
I use a LOT of precision measuring instruments in my work, though a hardness tester isn't one of them. My hand held rockwell tester has to be calibrated every use, to allow for temperature differences. Many of the precision gages at work are "user calibrated" no less than once per shift. Air spindles for bores, slide gages for ODs, indicator mics, regular mics, height stands, roll testers for gears, all are checked and rechecked during normal use. When you're measuring +-.0001, and .4999-.5002 is a tolerance you see nearly every day, it's that critical. Temperatures affect readings.

If your tester is not in a temperature controlled environment, that might be part of the new issue since you changed indenter. I'd calibrate the tester to read what the test block is verified to, and roll with it. After all, if you have a 60Rc test block, you want your machine to read 60Rc when testing it. If it does, you ARE in line with other testers. Like a lot of other measuring devices, hardness testers only show us a correlation between a known value and an unknown one, as your test block and your knife steel. "If my machine reads 60HRc on a verified 60HRc block, then I can be reasonably certain that when it reads 62 on my knife tang, it is, within acceptable tolerances, 62HRc."
Click to expand...
 
So those variables are out of the way, good on you for that. I would still calibrate the tested to the new indented, so that the machine reads a 60 Rc test block as 60Rc.
 
Keith Nix said:
So those variables are out of the way, good on you for that. I would still calibrate the tested to the new indented, so that the machine reads a 60 Rc test block as 60Rc.
Click to expand...

It reads what it needs to with the good indenter I use as mentioned in my previous post.

I bought the cheap indenter just to see how it performs.
 
DeadboxHero said:
Picked one up

lOkwX4g.jpg

mIGaxUO.jpg




I cleaned it, ran 15 tests on a piece of AEB-L to get the readings consistent and seat the indenter.


Ran it on the wilson blocks test blocks

It reads consistently 1 point low.

Which indenter is correct?

Well, I've been keeping tabs on my verification with my current indenter to keep track of my repeatability and reproducibility over time.

No changes in R&R since I first set mine up and I have been getting the same Rockwell hardness measurements as other makers and testers with similar protocols and steels.

So, if I match my machine to this indenter than I'm no longer in line with other folks Rockwell testing and the hardness reading on the steel would not be a good reflection of the microstructures I'm trying to control with time and temp.

So, the geometry is off on this budget indenter, this doesn't mean ALL of them will be reading 1 point low.
If bought another one it could be reading higher, or similar or low again. The tolerances in geometry, and surface finish on the indenter will cause variation like in the graph I showed in the earlier post.

At $30, it is to be expected there is going to be some variation to the tolanrances. On a $200-$400 part.

$30 is a steal of a price but it's important to understand the trade offs.

A better indenter is a Gilmore #101 made in the USA and is certified with NIST traceability $245

A replacement Diamond indenter from Grizzly is $396 which is overcharging but it is not a $30 indenter.
Click to expand...
It reads consistently 1 point low..... Ok , test block is 60 hrc and you get 59 hrc reading, right ? Why you simple not adjust tester to show 60 hrc ? What difference that can make ?
indenter PENETRATE in steel and tester measure how deep is that and show as HRC numbers .Different angle indenter will penetrate more or less ....So that s why we have KNOWN hardness steel .....adjust tester to show that hardness and that is that ? What I m missing here ?
 
Last edited:
Natlek said:
It reads consistently 1 point low..... Ok , test block is 60 hrc and you get 59 hrc reading, right ? Why you simple not adjust tester to show 60 hrc ? Adjust tester to show that hardness and that is that ? What I m missing here ?
Click to expand...



I answered why in post #12

"Keep in mind the tolerances won't be as good as a more expensive indenter and you may have to adjust your regulation plate to match the block.


Matching the block doesn't fix the source of the error, it just moves the error to the test forces to compensate for the indenter geometry thus adjusting an error with error to match the block.

You'll still get consistent readings.

It's just that your 61rc on a knife will be a different hardness on the same knife then another makers machine (higher or lower) amongst other things if the geometry of the cheap indenter is way off then a machine which has a proper indenter.

All this despite the fact both of you match your separate test blocks consistently at the same hardness, yet you'll both get different values on the same blade. Could be only by a little or a lot.

So It may be difficult to advertise a very specific hardness for the knives."

Also why post #19

"Which indenter is correct?


Well, I've been keeping tabs on my verification with my current indenter to keep track of my repeatability and reproducibility over time.

No changes in R&R since I first set mine up and I have been getting the same Rockwell hardness measurements as other makers and testers with similar protocols and steels.

So, if I match my machine to this indenter than I'm no longer in line with other folks Rockwell testing and the hardness reading on the steel would not be a good reflection of the microstructures I'm trying to control with time and temp."


Excerpt from Dick Dusharme at Quality Digest

"Tests have found that 90 percent of testers in use today do not apply the correct test forces or measure penetration depth correctly, says Tobolski.

The old, indirect method for verifying the correct operation of a Rockwell tester involved simply measuring a standard test block and verifying that the tester gave a value within the tolerance of the block. The feeling being that if the test read correctly, then the force and depth measurement systems must be OK.

"The problem with this method was that the person doing the indirect verification would adjust the tester to match the block," notes Tobolski. This "block chasing" could lead to incorrect test results on the customer's parts, he adds.

Tom Farrell, Mitutoyo test equipment product manager and E18 revision committee member, agrees. By mixing and matching test blocks and indenters from various manufacturers or by adjusting the tester, a tester can be made to read test blocks, he says. It was just such tweaking and the lack of standard reference materials that caused a one-point jump in hardness test results during the 1960s, claims Farrell. Testers chased blocks that, across industry, had been slowly drifting upward, rather than question the accuracy of the blocks or the indenters they were using.

Also an excerpt from a NIST recommend practice guide.

tOTLXZX.jpg
 
DevinT said:
Boom!
Yeah, Natlek never passes up on a chance to say something stupid, or at least cringe worthy.

Hoss
Click to expand...
Devin Thomas ........................it was question, read end of my post .Says , WHAT i m missing here and i get answer from BBB...So how it s going , did you still use toaster oven for temper your knives :D
 
DevinT said:
Boom!
Yeah, Natlek never passes up on a chance to say something stupid, or at least cringe worthy.

Hoss
Click to expand...
OK , let me tell you something ....personally i don t give ***** what you think about me or about your opinion about whatever it is .But addressing other members in this way is not good for this forum .No , it is not about me I can handle that ,especially from someone like you :thumbsdown: but think how some of other members here can take post like that ....better no say anything / even that maybe would be correct/ then get quote like this ......
There was polite way how to say when someone is wrong or whatever you want to say to that person .Addressing other member in your way just SPEAK of your personal ... ...you know what , right ?
Please don t quote me again , I have no time for wasting with someone like you :thumbsup:

Natlek
 
Last edited:
DeadboxHero said:
I answered why in post #12

"Keep in mind the tolerances won't be as good as a more expensive indenter and you may have to adjust your regulation plate to match the block.


Matching the block doesn't fix the source of the error, it just moves the error to the test forces to compensate for the indenter geometry thus adjusting an error with error to match the block.

You'll still get consistent readings.

It's just that your 61rc on a knife will be a different hardness on the same knife then another makers machine (higher or lower) amongst other things if the geometry of the cheap indenter is way off then a machine which has a proper indenter.

All this despite the fact both of you match your separate test blocks consistently at the same hardness, yet you'll both get different values on the same blade. Could be only by a little or a lot.

So It may be difficult to advertise a very specific hardness for the knives."

Also why post #19

"Which indenter is correct?


Well, I've been keeping tabs on my verification with my current indenter to keep track of my repeatability and reproducibility over time.

No changes in R&R since I first set mine up and I have been getting the same Rockwell hardness measurements as other makers and testers with similar protocols and steels.

So, if I match my machine to this indenter than I'm no longer in line with other folks Rockwell testing and the hardness reading on the steel would not be a good reflection of the microstructures I'm trying to control with time and temp."


Excerpt from Dick Dusharme at Quality Digest

"Tests have found that 90 percent of testers in use today do not apply the correct test forces or measure penetration depth correctly, says Tobolski.

The old, indirect method for verifying the correct operation of a Rockwell tester involved simply measuring a standard test block and verifying that the tester gave a value within the tolerance of the block. The feeling being that if the test read correctly, then the force and depth measurement systems must be OK.

"The problem with this method was that the person doing the indirect verification would adjust the tester to match the block," notes Tobolski. This "block chasing" could lead to incorrect test results on the customer's parts, he adds.

Tom Farrell, Mitutoyo test equipment product manager and E18 revision committee member, agrees. By mixing and matching test blocks and indenters from various manufacturers or by adjusting the tester, a tester can be made to read test blocks, he says. It was just such tweaking and the lack of standard reference materials that caused a one-point jump in hardness test results during the 1960s, claims Farrell. Testers chased blocks that, across industry, had been slowly drifting upward, rather than question the accuracy of the blocks or the indenters they were using.

Also an excerpt from a NIST recommend practice guide.

tOTLXZX.jpg
Click to expand...
Thanks :thumbsup: So for most knife maker one point more or less would not make huge difference , especially when we look at the price of indenter...... 400$ to 30 $ .
Used the $30 indenter trended 1rc low.
Click to expand...
 
Natlek said:
OK , let me tell you something ....personally i don t give ***** what you think about me or about your opinion about whatever it is .But addressing other members in this way is not good for this forum .No , it is not about me I can handle that ,especially from someone like you :thumbsdown: but think how some of other members here can take post like that ....better no say anything / even that maybe would be correct/ then get quote like this ......
There was polite way how to say when someone is wrong or whatever you want to say to that person .Addressing other member in your way just SPEAK of your personal ... ...you know what , right ?
Please don t quote me again , I have no time for wasting with someone like you :thumbsup:

Natlek
Click to expand...
90% of the time you seem to want to antagonize all good threads. You are not the forum police, but you always want to interrogate people posting.

It will help if you can stop arguing all the time.

Hoss
 
DeadboxHero said:
My Rockwell tester kept, indoors in a clean place away from the shop with central heating and cooling. ISO recommends testing at 23°C +/- 5° C
Thermostat reads 23.3° C / 74°F

I was just using it earlier today, read everything fine.

Used the $30 indenter trended 1rc low.

Switched back.

Everything back to normal.

Same temperature, same day, same tester, same operator, same procedure.



.
Click to expand...
I would be interested in seeing what your weight stack weighs. I just picked up a second one and would like to compare it to what yours weighs. My new one weighs 5452g my old one weighs 5524g. And with my wilson 60.5 +-.5rc test block both weights read the same within any discernible difference. When I drop down to my 48.5rc block thy are different by up to .5rc. with the new tester being closer to the actual test block number.
 
DevinT said:
90% of the time you seem to want to antagonize all good threads. You are not the forum police, but you always want to interrogate people posting.

It will help if you can stop arguing all the time.

Hoss
Click to expand...
In the meantime you are playing forum police ? Priceless :thumbsup: I would really appreciate if you open somewhere new topic and use some links to point me where i do that so i can see what i m doing wrong here ...maybe you're right , but I don't know where I do it. I know that my intentions are not like that so if you can find thread where i do that ..............:thumbsup:
I can bet that 99% of that 0.001 % knife maker who have hardness tester would buy cheap one indenter when times come to replace it ...And even if you buy 300 $ one , you must adjust tester ....300 dollar one i just look at come in range of 120° ±0.35°
 
Last edited:
Natlek said:
In the meantime you are playing forum police ? Priceless :thumbsup: I would really appreciate if you open somewhere new topic and use some links to point me where i do that so i can see what i m doing wrong here ...maybe you're right , but I don't know where I do it. I know that my intentions are not like that so if you can find thread where i do that ..............:thumbsup:
I can bet that 99% of that 0.001 % knife maker who have hardness tester would buy cheap one indenter when times come to replace it ...And even if you buy 300 $ one , you must adjust tester ....300 dollar one i just look at come in range of 120° ±0.35°
Click to expand...
I think you should buy and use the cheap one.

Just like all things knife making, the better the equipment, and the more experience = best results.

Hoss
 
Got the Gilmore NIST tracable Certified Indenter.

xowLCSG.jpg


GqIRm2f.jpg


The repeatability and reproducibility is better than both the Grizzly indenter and especially the $30 MXBAOHENG indenter.

Now that I've used all three, I can say that the Gillmore is a worthy upgrade for discerning hardness test users.
 
You must log in or register to reply here.
Back
Top