This problem has started a huge stink where I work.
The tester I was using is a production test fixture, as WIP parts that come out of an HT oven are checked on it immediately after quench. I am not too familiar with the work flow process, but both aged aluminum and HT steels are checked at this particular station.
It seems that someone in a non-technical role made the decision to start checking aluminum on the Rockwell tester using a C indenter, therefore consolidating test instruments. I told the area supervisor that whatever results he was gaining from the tests were meaningless. (He told me that no one ever complained before me.) I asked him what happened to the aluminum hardness tester, he said that it had been gone for a good year, probably in storage somewhere. I dug out a handheld Webster checker and told him to start using that in the meantime, please!
Upon inspecting the indenter more closely, I found that when the aluminum sheet was tested on the Rockwell, the metal was so malleable (and the sheet thickness so thin) the intenter would punch right through the specimen and hit the hardened steel "table" holding the piece. The indenter is basically crap, and probably has been broken for a while.
I was getting pretty mad at this point, but I realized that the area supervisor didn't know any better. I asked him for the last year's worth of data, which I'll analyize later today. (I am not going to be surprised if the data doesn't deviate more that 5 points for the entire sample of two different metals.)
My best guess is that the production guys were "fortunate" to have the Tester read incorrectly within the range they were aiming for, coupled with the idea that they thought the hardness of aluminum and steel should be equal. The test wasn't a GO/NO GO qualifer, it simply was data gathering for process adjustment purposes. No one had ever explained to these guys the theory, intent, and necessity of the test they were conducting. They were simply recording numbers.
(As far as product liability, all of this metal is used in a decorative fashion, no load bearing beams or structural members have been compromised...) I still have a huge problem to backtrack through. God knows how many other production areas have been affected by this screw-up.
The root cause of the problem here is that the engineer who is responsible for this area never leaves his office. I have not been working long, but I know to be on the floor everyday as much as I can. You simply cannot do your job well if you operate far from where it is occuring. He could have caught this a year ago, but since he is rather removed from the operation it slipped right on by him.
Anyway, I just wanted you all to know this problem, hopefully explaining the weird results I reported above. I will re-test the "bronze" part in question later, and hopefully ascetain what it indeed is composed of.
Thanks for all your replies.
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. Nice discussion.
