Ive been helping out and doing some free hardness testing for other makers on occasion to help other makers build hardness curves.
I figured I'd share a FYI about some of the dos and Don'ts of processing for hardness testing since this information seems rather esoteric and is a lot of work when things are not processed properly.
Nicely labeled is always nice.
However, stamped letters have raised surface so the back will not sit flat on the test anvil, this means no accurate readings can be made unless ground flat.
The same goes for having decarb, scale and mill scale on the back, it all needs to be removed and flat.
Flatness is also a big concern as well as minimum thickness for testing. Can't be too thin. (Under 0.030" in most cases depending on the hardness)
Here is an example of a nicely processed condition. Flat and good finish.
The back doesn't need a high finish just needed to be flat.
Hardness testing is easy. The hard part is getting things flat and nicely finished for testing.
That is the first thing that needs to be ruled out when having problems with inconsistencies in values or values that are too high or too low.
Have to rule out flatteness then surface finish.
