Anyone ever have a hardness tester go nuts on you?

[godogs57]

My hardness tester, bought perhaps 20 years ago from Kovall's, has decided to belly up on me. Wondering if you ever had anything like this and what did you do to fix it. Mine came from India and was purchased here in the US. I doubt there is anywhere I can go to get it serviced.

Readings are all over the place now, but were consistent for the last 19 years. Following the same ht formula I've always used for CPM154, I'll always end up with 60.5-61.0 Rockwell. For the last 8 months to a year I'll get a reading of, say, 50.0 on a blade, re test and get 65.0. Re test and get some other figure that makes no sense. Then I'll get 61.0 perhaps...maybe not. I love to tinker like the rest of us here and decided to take it apart, excepting the mechanism that clearly states not to disassemble. I honestly don't think the diamond tip is bad. I've examined it under magnification closely and it appears good. I have three test blocks I bought with the tester, all calibrated in the 55-60 range...sometimes the tester hits it and sometimes it will register light....in the 45-50 range.

One thing I've noticed is the dial after I sink the diamond tip. I think the problem might be with the dial itself. After sinking the diamond tip the dial might move around to, say 9 o'clock. On the re try, It might settle at 5 o'clock that time, as if there is something binding in the dial mechanism. Then when I move the lever to get the Rockwell reading the dial's needle "skips" two or three tick marks before rotating around to the final reading. It never did that before either...

I took the top cover off and cannot see any binding or rubbing of the rods connecting the weights to then dial.

Any suggestions? Hardness testers are super expensive nowadays....I would hate like crazy to have to buy another one.

 

[DeadboxHero]

My hardness tester, bought perhaps 20 years ago from Kovall's, has decided to belly up on me. Wondering if you ever had anything like this and what did you do to fix it. Mine came from India and was purchased here in the US. I doubt there is anywhere I can go to get it serviced.

Readings are all over the place now, but were consistent for the last 19 years. Following the same ht formula I've always used for CPM154, I'll always end up with 60.5-61.0 Rockwell. For the last 8 months to a year I'll get a reading of, say, 50.0 on a blade, re test and get 65.0. Re test and get some other figure that makes no sense. Then I'll get 61.0 perhaps...maybe not. I love to tinker like the rest of us here and decided to take it apart, excepting the mechanism that clearly states not to disassemble. I honestly don't think the diamond tip is bad. I've examined it under magnification closely and it appears good. I have three test blocks I bought with the tester, all calibrated in the 55-60 range...sometimes the tester hits it and sometimes it will register light....in the 45-50 range.

One thing I've noticed is the dial after I sink the diamond tip. I think the problem might be with the dial itself. After sinking the diamond tip the dial might move around to, say 9 o'clock. On the re try, It might settle at 5 o'clock that time, as if there is something binding in the dial mechanism. Then when I move the lever to get the Rockwell reading the dial's needle "skips" two or three tick marks before rotating around to the final reading. It never did that before either...

I took the top cover off and cannot see any binding or rubbing of the rods connecting the weights to then dial.

Any suggestions? Hardness testers are super expensive nowadays....I would hate like crazy to have to buy another one.

It would help if you recorded a short video of performing a test and posted it here, that would help rule a lot of things out.

 

[godogs57]

Might have to.....I can't record movies (droid phone) but can try and post pics.

 

[JTknives]

I put my money on you diamond brale. I have had such issues and it’s usually a chipped diamond causing it. You will need a 10x loop to see it but if you look at the very point it should be perfectly smooth and rounded. Here is a picture of one of mine that is chipped. I have 7 of these that are defective. I thought about drilling a hole through them and making a necklace for the wife lol.

 

[DeadboxHero]

G godogs57
Diamond Indenters are expensive,

I would confirm if is a diamond Indenter issue first before purchasing one. Usually a damaged indenter will give false high hrc erratic readings since it is not penetrating as deep without the sharp point.

To confirm it's your indenter and not another issue switch out the diamond indenter out for the HRB ball indenter and see if the test readings are also running low and erratic.



The ball Indenter is always included with a Rockwell tester in the accessory case with the blocks. There should also be a HRB test block as well.

Change the weight to 100kgf

Do this by turning the dial to 100kg if you have a HR-150A style model.

If different, than just remove the top, 2kg weight from the hanger on the back.

Test on the block and see if you're still getting consistently low readings or erratic readings on the HRB block.

Make sure the indenter is fully seated and clean and that the anvil is clean, I recommend using the small test anvil.

The first couple readings will be a little off from the block until the indenter, test block and anvil are fully seated.

If the readings are still erratic and low than it is not the diamond indenter causing the problem.

 

[JTknives]

G godogs57
Diamond Indenters are expensive,

I would confirm if is a diamond Indenter issue first before purchasing one. Usually a damaged indenter will give false high hrc erratic readings since it is not penetrating as deep without the sharp point.

To confirm it's your indenter and not another issue switch out the diamond indenter out for the HRB ball indenter and see if the test readings are also running low and erratic.



The ball Indenter is always included with a Rockwell tester in the accessory case with the blocks. There should also be a HRB test block as well.

Change the weight to 100kgf

Do this by turning the dial to 100kg if you have a HR-150A style model.

If different, than just remove the top, 2kg weight from the hanger on the back.

Test on the block and see if you're still getting consistently low readings or erratic readings on the HRB block.

Make sure the indenter is fully seated and clean and that the anvil is clean, I recommend using the small test anvil.

The first couple readings will be a little off from the block until the indenter, test block and anvil are fully seated.

If the readings are still erratic and low than it is not the diamond indenter causing the problem.

Or just pull it out and look at it under the loop. New brales can be picked up for $20-30. Yeah thy are Chinese made but I know a few guy that use them and thy are spot on for them. I’m Still using Wilson brales so I have not had to use one.

 

[12345678910]

low on oil ?

 

[godogs57]

I'll check my oil levels and also switch out to my ball indenter and see if its inconsistent as well. Thanx for the suggestions.

Where can I find another diamond indenter if thats the case?

 

[Stacy E. Apelt - Bladesmith]

ebay.
https://www.ebay.com/sch/i.html?_fr...d+brale+indenter+for+hardness+tester&_sacat=0

 

[godogs57]

followup: switched to the ball indenter and three straight readings exactly the same. Switched back to the diamond indenter and three readings on the 61.5 Rc test block read 61, 62 and 64 Rc. Not dead on, but closer than 50, 61, 65 which was the stuff I was seeing before. Obviously not close enough to depend on for a good reading though. Probably going to try a new diamond indenter.

 

[JTknives]

We are actually looking at importing a quantity of them and offering them on our site. The normal shipping time for these is usually really long. Ours would be tested on our Wilson tester to make sure it’s in range in our test block.

 

[DeadboxHero]

Amazon

"MXBAOHENG HRC-3"

$30 with prime shipping

That way you don't have to deal with the Overseas shipping.


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.

Not a big deal for ballparking hardnesses but if trying to hit peak hardnesses or make conclusions about a specific hardnesses through R&D compared to other folks readings it can be an overlooked component in why things are different between other testers amongst other things.

A low cost indenter can be the metrological equivalent of a forge HT which is good enough for some, others just not enough control in the end result.

The spec for the indenter is 200um on the tip radius and 120° on the cone angle with a surface good finish on the features so that a rough finish doesn't interfere.

On the graph below, you can see how the minor variation to the indenter geometry with different indenters will cause variation when testing blocks at the same hardness, same machine, same operator but different indenters that look the same to the eye.

So it adds cost to get an indenter with tighter tolerances closer to the specifications let alone a NIST tracable certified Indenter.

Could be a tough choice for some or a no brainier to others with either selection.

followup: switched to the ball indenter and three straight readings exactly the same. Switched back to the diamond indenter and three readings on the 61.5 Rc test block read 61, 62 and 64 Rc. Not dead on, but closer than 50, 61, 65 which was the stuff I was seeing before. Obviously not close enough to depend on for a good reading though. Probably going to try a new diamond indenter.

 

[Stacy E. Apelt - Bladesmith]

It certainly sounds like a bad indenter. I will also add that if the machine is older you may need to thoroughly clean and lube it. There could even be insects or a mud wasp nest inside causing the issue.

 

[JTknives]

It certainly sounds like a bad indenter. I will also add that if the machine is older you may need to thoroughly clean and lube it. There could even be insects or a mud wasp nest inside causing the issue.

funny you bring this up. My small portable one I have was giving me weird results and I could not figure out what was going on. The brale was good and everything else seemed good. I opened up the side cover and found a mouse nest in there. No mouse just a bunch of stuffing that was stuffed in there For future mouse use.

 

[JTknives]

Amazon


"MXBAOHENG HRC-3"


$30 with prime shipping


That way you don't have to deal with the Overseas shipping.



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.


Not a big deal for ballparking hardnesses but if trying to hit peak hardnesses or make conclusions about a specific hardnesses through R&D compared to other folks readings it can be an overlooked component in why things are different between other testers amongst other things.


A low cost indenter can be the metrological equivalent of a forge HT which is good enough for some, others just not enough control in the end result.


The spec for the indenter is 200um on the tip radius and 120° on the cone angle with a surface good finish on the features so that a rough finish doesn't interfere.


On the graph below, you can see how the minor variation to the indenter geometry with different indenters will cause variation when testing blocks at the same hardness, same machine, same operator but different indenters that look the same to the eye.






So it adds cost to get an indenter with tighter tolerances closer to the specifications let alone a NIST tracable certified Indenter.


Could be a tough choice for some or a no brainier to others with either selection.

I know we don’t see eye to eye on a few things but to go from trusting your hardness tester to it’s good for a ballpark because of a Chinese Brale is a bit far fetched. Especially considering one of the most popular currently available hardness testers is made in China (grizzly). Even Chinese brales have tolerances and thy are written on the container. As well as the HRC error to be added or subtracted. If you match the tolerances listed to your chart you will see you are looking at very little variance. Especially if you consider most test blocks are Given a +-1rc tolerance. I use a +-.5rc block but thy are very expensive and not standard issue so to speak. Funny thing is hardness testers are calibrated by adding or removing weight so it falls within the range of the gauge block. The base weight and hanger are adjusted to read correct then when the other weights are added thy fall within the proper scale range as well. So as long as your new brale falls within the hardness tolerances of your gauge block your good to go. You could possibly see an exacerbation of error if your measuring all the way down down to single digit RC but rarely do we measure below 45rc and that’s just for springs. But generally we sit in the 58-67 range. So when buying Chinese brales double check the tolerances listed.

 

[godogs57]

I know we don’t see eye to eye on a few things but to go from trusting your hardness tester to it’s good for a ballpark because of a Chinese Brale is a bit far fetched. Especially considering one of the most popular currently available hardness testers is made in China (grizzly). Even Chinese brales have tolerances and thy are written on the container. As well as the HRC error to be added or subtracted. If you match the tolerances listed to your chart you will see you are looking at very little variance. Especially if you consider most test blocks are Given a +-1rc tolerance. I use a +-.5rc block but thy are very expensive and not standard issue so to speak. Funny thing is hardness testers are calibrated by adding or removing weight so it falls within the range of the gauge block. The base weight and hanger are adjusted to read correct then when the other weights are added thy fall within the proper scale range as well. So as long as your new brale falls within the hardness tolerances of your gauge block your good to go. You could possibly see an exacerbation of error if your measuring all the way down down to single digit RC but rarely do we measure below 45rc and that’s just for springs. But generally we sit in the 58-67 range. So when buying Chinese brales double check the tolerances listed.

So Jarod, just so I get this right, tell me what I’m seeing regarding the tolerances written on the container?

+0.1 on the bottom pic...what does that represent in this case and how would I apply that to my situation? I’m using the same indenter that came with the hardness tester 20-something years ago. The fact that it is this old makes me understand that it’s probably trashed at this point, as others have guessed. This original indenter had no such tolerances listed on the container.

thanx!

 

[DevinT]

Check the shaft that moves the dial and make sure it’s not sticking. I’ve seen them become gummy over time.

Hoss

 

[JTknives]

Check the shaft that moves the dial and make sure it’s not sticking. I’ve seen them become gummy over time.

Hoss

This is a good idea. When I went through mine I found it was sticking a little. It just needed adjustment as it’s rather precise how the gauge lever sets in the brale shaft.

 

[DeadboxHero]

So Jarod, just so I get this right, tell me what I’m seeing regarding the tolerances written on the container?

+0.1 on the bottom pic...what does that represent in this case and how would I apply that to my situation? I’m using the same indenter that came with the hardness tester 20-something years ago. The fact that it is this old makes me understand that it’s probably trashed at this point, as others have guessed. This original indenter had no such tolerances listed on the container.

thanx!

Picked one up

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.

 

[Keith Nix]

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."