hardness test blocks

[CWendling]

Got a deal on a tester, but had a question on test blocks. Do they last forever? Still good even if the majority of surface has been tested? Just find a spot that wasnt tested? Does it matter if you test a spot that was already tested? Source for blocks cheaper than MSC ($100 ea). I know its pretty close as I had a machine shop test some coupons with their $10K tester and my readings are pretty close to theirs. Thanks

 

[JG Custom Metal Works]

I don’t see why they wouldn’t last forever. If the whole surface, on both sides have been tested, and there isn’t anymore space to test, I’d probably grind it down on a surface grinder(you want it to be perfectly flat) and finish it to 400 grit. Then see if it tests out at the listed hardness on that block. Make sure to note the hardness if it’s on the face that will be ground off(of course). I wouldn’t test it on the same place twice. It just doesn’t seem to me like that would be accurate.

You can buy a 5 piece set of testing blocks from Grizzly for $126.50.
https://www.grizzly.com/parts/Grizzly-TEST-BLOCKS-5PC/P9645037

 

[timgunn1962]

Making the indentation is doing work, so it causes work hardening.

There's a minimum recommended distance between impressions to maintain accuracy.

If you surface grind the indentations off, you'll need to grind deeper than the bottom of the indentations to remove any work-hardened material around the tip of the indentation to get to consistent hardness.