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Posted: 5/20/2011 4:05:10 PM EDT
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i posted this on the TFL forum, just in case someone over there saw it that doesnt come here.
ive got a somewhat stupid question. i have a sidemarked polytech receiver that im slightly curious about the hardness of. serial number 165xx. at work the other day i noticed that we have an old school hardness tester that we use for checking crankshafts with. its the type that has the metal ball inside it –– you let it impact the part youre testing and you read the measurement on the side of the tool. obviously its non-destructive and its only going to test surface hardness. would this be an acceptable way to see if my receiver is hard enough to trust? is it any more accurate than taking a file to it? we use it on crankshafts that literally cost millions of dollars, but thats a different use and a different industry. also, the tester has a current calibration sticker on it, if that matters to anyone. |
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Well, using that instrument is how it's supposed to be done.
You do need the proper stylus (ball). To get accurate readings in a specific range you need the stylus appropriate for that range. Crankshaft tester??? What hardness levels and Rockwell/Brinell scales do you use for crankshaft testing? Are those the same approximate range you expect of the receiver? |
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good question. i have no idea. the welders are the ones who use it the most. i recall that the range on the side of the tool goes up towards one hundred on the C scale, but i dont know what stylus is in it.
ill find out on monday. do you know what the acceptable surface hardness of the m14 receivers is supposed to be? |
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The only thing to keep in mind is you will need to find out exactly what hardness and what scales you're dealing with. Both for what the receiver is specified for and what your tester reads.
I have seen hardness measurements in Brinnell, Rockwell, B scale, C scale etc. Just make sure you are talking the same units for everything. There may be some conversion charts between Brinnell and Rockwell. |
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i looked at the tester we have today. its old, so i dont know if the company that makes it is still in business. the name on it was Detroit Hardness Tester.
it is very similar to this one........... http://www.detroitflame.com/HardnessTester.htm for only 105 bucks, its great for doing quick spot checks. like the other guys said though, its only surface hardness youre checking. ours passed its calibration check, so it cant be but so bad. |
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