hardness tester: precise but not accurate?

T

Travis Fry

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Jun 11, 2010
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I just got a new-to-me benchtop hardness tester. I don't recall the brand at the moment, but it was made in the USA and is similar to the Wilson types. Everything appears to be in remarkably good condition. I've been fiddling around with it, and I get consistent (precise) readings with my test block. THe problem is that my readings on my 62.4 HRC block come out around 58 (not accurate).

-Could this be due to my technique? Indenter and anvil are in great shape, and the block is perfectly flat. I could still be doing something wrong.

-Could it have anything to do with how I installed the weights? The weight holding rod was detatched, and though reattaching seemed fairly simple (the rod had a female threaded hole that screwed onto a small male end inside the tester), I wonder if this could affect readings?

-When I pulled it out of my car, I saw that some light oil had leaked out of the top (it had to be layed on its side for travel). It didn't appear that much leaked out, but could the oil level (wherever it is kept) be affecting my readings? How would I check and how would I know?

I want to reiterate that I seem to be getting consistent (precise) readings, but they aren't accurate.

Any help with 1) figuring out what is wrong and 2) fixing it would be appreciated.
 
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The oil pot needs the right amount of oil, you need to add some. Most take 5 wt synthetic.

Look at your diamond point real close and make sure there is no damage.

The anvil need to be clean, flat and well seated.

Technique, are you setting the pre-load right?

These things do need calibrating, but I can't tell you how to do it.
 
Mine is a import and every time I move it I have to recalibrate it. Look online for a tech manual for your type of tester and it should have a section on how to recalibrate it.
 
An update: I played with this thing for a good while last night and figured out that there's a little knob inside that was loose. I tightened it, and found that it being loose was preventing the tester from applying the load correctly. After, the load lever was a good bit stiffer and my readings more consistent and much closer to the test block. I'm still reading about 1 point lower than the block, but it's much more consistent. I'll take the top cover off tonight if I can in order to check the oil level, and then will see where I can go from there.
 
Travis, on top of what Don said, on mine taking apart the whole linkage and giving it a good cleaning/oiling to get the smoothest action possible did help.
 
Like Patrice said, mine was pretty gummed up and needed a good cleaning / oiling.

This was after I got all the dirt dobber nests out of it...
 
Not to beat a dead horse but about the cleaning/oiling. Do it even if you feel it is already pretty smooth. That's what I thought on mine and was surprised how smoother it made the action.
 
Patrice Lemée;13555224 said:
Not to beat a dead horse but about the cleaning/oiling. Do it even if you feel it is already pretty smooth. That's what I thought on mine and was surprised how smoother it made the action.
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I think this is a good idea. Any recommendations for specific oils or products I should use or avoid? I'm generally a fan of the Rem Oil I use on my guns for things like this, but am very open to suggestions/advice.
 
Travis Fry said:
I think this is a good idea. Any recommendations for specific oils or products I should use or avoid? I'm generally a fan of the Rem Oil I use on my guns for things like this, but am very open to suggestions/advice.
Click to expand...

Rem oil is fine. Treat it like gun as far as cleaning & oiling.
 
I ask around at machine shops and check with other makers. Also a used machinery sales place two hours from here that I bought two Rc testers from last year. Came close to buying one off ebay a while back also.
 
Travis, when checking the condition of the penetrator, try looking at the indentation on the test block under a microscope, its easier to see a defect.
 
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