Rockwell Force Testing vs. ASTM E-18 (02 version)

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SteelMan

We have been considering calibrating our own Rockwell hardness machines (testers). In the newest revision of ASTM E-18 (02 version); it discusses the process of verifying the force of the penetrating mechanism. It appears that we must simply use a measuring device to measure the force delivered at the different scale ranges. If anyone has any experience with this, please voice your opinion on the best practice going forward. I really need to know how to test the force for calibration purposes. I think I have a grasp on the remaining subjects in reference to calibrating hardness testers. I am not interested in an outside lab. We have so many machines and there are so few qualified and registered firms in the area, that our answer is to perform this calibration in house. Thanks for any help or advice in advance.
 
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Jimmy Olson

Steelman,

The company I used to work at had a number of hardness testers that we calibrated in house. We simply purchased NIST traceable test blocks and used those to calibrate the testers. Those blocks were designated as cal use only and were locked up so that they weren't being used for anything else. This satisfied every requirement that we came across. If you want I can give you the name of the company that we got our blocks from.

This is also the way that most cal labs check hardness testers (I've worked at a couple labs myself). I hope this helps.
 
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SteelMan

First of all, thanks for the reply.

I would be interested in getting the name of the block company. Also if you have a calibration procedure that you would share with me I would be interested in seeing what you had done with your procedure.
 
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Jimmy Olson

Here is a link to the company that we got our blocks from

http://www.hardness-testblocks.com/

I don't have a copy of the procedure anymore, but what we did was pretty simple. We basically used the certified block as a reference standard and did three tests and ensured the reading was accurate. Depending on the tester and the range we would use just one block or several blocks. I might have a copy of a procedure at home. I'll look tonight and will get that for you if I have it.
 
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SteelMan

Thanks, this is Patriot, is that correct. I have bought the ellis blocks before. It was interesting to see that you only took 3 readings. Did you feel comfortable with taking only 3? I am assuming that you also took test on every scale that you used. 15T, 30T, 45N, etc.? Thanks for the information.
 
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Jimmy Olson

We were comfortable with three readings for a couple reasons. One was that we checked our testers every three months. The other was that our testers were basically used for reference and were not critical. I've heard of some people doing more checks and even some people of only doing one. I think it depends on what you feel comfortable with depending on circumstances.

We did check each range depending on what was used. We had blocks for each of the scales, and different values within the scales (we had several blocks for C since that was what primarily used). We determined what each tester was being used for depending on the area and then determined what needed to be checked on it. For example, one tester was only being used to check at about 60hrc, so we only checked that one at one value. While another tester was used at a number of ranges, including superficial, and that one had considerably more checks.

That's one nice thing about doing it internally. You can determine what is important and what you want to check. :D
 
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tomvehoski

I also agree with using NIST traceable test blocks. I used to have a company come in annually to service the machines (clean, repair, etc.), but we did daily checks with test blocks. We did hundreds of hits a day, so we typically had the inspectors check the machine at least at the start of each shift.

One thing to watch - test blocks are typically only accurate within +/- .5 point (HRC). This can be a point to argue with customers who have digital testers if they reject because you were out 0.1
 
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