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01-01-2010, 11:16 PM #1
Calibrating a Rockwell hardness tester?
Can the average person calibrate a Wilson Rockwell hardness tester? It's a manual, not a digital. Is there a certified test piece that I would need?
01-01-2010, 11:58 PM #2
www.mcmaster.com catalog page 2269, halfway down the page.
The C range blocks are about $58, 1.5" x 2.5" x 0.25" thick. They come with an NIST certificate of calibration. You specify the desired hardness when you order.
01-02-2010, 02:37 PM #3
That's not bad. Is it fairly straight forward to adjust the machine myself?
01-02-2010, 04:10 PM #4
01-02-2010, 04:25 PM #5
Oliverdude - I posted some pages from a manual here - http://www.practicalmachinist.com/vb...=1#post1267805
Sorry about the quality, they are scans of photocopies. The adjustment is on the 3rd and 4th images in the second post. I hope this helps you, even if your tester is not the same model, the process is the same.
For calibration, you need several test blocks to cover the range you test. An improperly adjusted tester can be correct at one hardness, and off at higher and/or lower levels. It's best to have blocks for the hardness level you want to test, and check it regularly.
01-02-2010, 04:34 PM #6
I had to recalibrate my tester after moving several years ago dispite unloading the bearing edges and blocking internal parts from moving. The adjustment was behind a removable plate and obvious as the nearest in the linkage and only place there was a socket set screw with lock nut close to the readout dial.
It came with 52, 56 & 62rc and blocks for other scales also. I only use one rc block as it is accurate with all once set. It does vary slightly with room temp but not much. After the recalibrate 5+ years ago its' never needed another redo.
Hope that helps.
01-02-2010, 04:42 PM #7
Just remember that whichever side you use is the only side you use...nothing dumber than turning the sample over and trying to use the other side.
01-02-2010, 05:50 PM #8
You'll also want to check the condition of the diamond penetrater. These can fracture in careless use, leading to erratic readings.
01-02-2010, 06:41 PM #9
01-02-2010, 07:27 PM #10
01-02-2010, 07:33 PM #11
Each test dimple raises a circle of material around it. If you turn the test block over and apply pressure, the raised material will compress under the test load and will throw the reading off slightly.
I wouldn't call it stupid, unless you knew it was going to happen and did it anyway.
01-02-2010, 08:31 PM #12
Thanks for the scans. Atleast I will kind of know what is involved before I finish the deal.
01-02-2010, 10:06 PM #13
Also, not two readings on a test block should be within 3 dimple diameters to one another. The material deformation can cause erroneous readings.
And yes. YOu can check all the way out on the edge of the disk. The leverage caused by the cantilever type effect does not impact reading.
As far as adjusting the machine, I don't know how to do it. I think if you are making important decisions from the machine that you should have someone qualified to do it (A2LA certified if you are trying to achieve Quality Standards). If you are supplying quality registered companies, they will eat you alive for adjusting it yourself instead of calling someone A2LA accredited.
But then again, If you know what you are doing, you can add it to your calibration scope in your quality manual and you are all set.
01-02-2010, 10:14 PM #14
It does happen occasionally.
We also get test blocks from Wilson