I had check class 45 cast iron and would not fit in Rockwell tester.
Rutland had a unit for none destruction testing I purchased and very simple . A 3/16 ball from ball bearings. And a clear tube . It work but easy to lose the small ball so I up size so easier to find the ball. Then used a paint stick good and bad marks . Now my crew could check the hardness too. They set wheel on floor and drop ball. In time a rug around the wheel stop ball from hiding . The pickup ball and check next wheel. We did not check every wheel just in in each batch.
Then when looking materials it came handy too.
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Dave
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FYI I still have the test disk from Rockwell hardness test I think last for ever it never leaves a mark
davesmith1800