Help solving hardness measurement difference
Help solving hardness measurement difference
(OP)
Hi, I am having hardness (both RC and R15N) measurement difference with my heat treating supplier. My measurement is usually 1-2 points higher than my supplier's. We did a hardness correlation study with 15 parts engraved with numbers so that everyone measures the same part. My average is RC 54.5 and R15N 87.6. The heat treating supplier average is RC 52.8 and R15N 85.9. The heat treating specification is RC<54.
We are all trying to understand why this happens since we already tried to standardize everything (anvil size, measurement location).
Any input is highly appreciated.
Thank you
We are all trying to understand why this happens since we already tried to standardize everything (anvil size, measurement location).
Any input is highly appreciated.
Thank you





RE: Help solving hardness measurement difference
RE: Help solving hardness measurement difference
If you really want to get an idea you could use a microhardness standard and check it on both pieces of equipment. Then you verify the measurement by doing a knoop/vickers test next to the 15N or HRC measurment.
Why are they different? Now that is a tougher question to answer, but the mechanisms for applying the loads may not be exactly the same.
You mention you have standarized the anvil and location...
but are you using the same types of eqipment (mechaincal vs. load cell)?
RE: Help solving hardness measurement difference
That is, if you had a standardized test block that was certified as 43.7 HRC +/- 1 and got these results on both machines, they both would be considered acceptable.
Standardized test blocks are generally made to tighter controls on the uniformity of the hardness as well as surface finish than routine parts, so the differenct you are seeing doesn't indicate there is anything wrong.
rp
RE: Help solving hardness measurement difference
RE: Help solving hardness measurement difference
You need to do that.
Be rigorous on the method and statistics, then you will know if it is significant.
I have never seen a hardness study that reported they could do any better than RC 50 +/-1.5. It is the nature of the beast.
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Plymouth Tube
RE: Help solving hardness measurement difference
RE: Help solving hardness measurement difference
I am going to send standard hardness blocks (RC and R15N) to my heat treating supplier to see if we have the same readings.
Both sides all calibrate hardness tester with a standard block everyday. And both sides hardness tester are calibrated by third party every 6 months.
I will also check if the same types of equipment (mechanical vs. load cell) is used.
Have a nice weekend :)
RE: Help solving hardness measurement difference
What is the hardness of the calibration block used every day? It is best if it is close to the values you are trying measure on your parts.
RE: Help solving hardness measurement difference
RE: Help solving hardness measurement difference
John
Denial ain't just a river in Egypt...Mark Twain