Rockwell Test Block

[kootenay joe]

I have had this "Rockwell Test Block" for some time. The pouch it came in is disintegrating and the instruction sheet is stained and hard to read.
On the front side of paper is "Calibration" and "Inspection". Looks like it was tested three times: the first number is Calibration and the second, inspection: 63.2 / 63.5, 63.4 / 63.2(?), 63.4 / 63.3.
One side of this round 'block' is covered with tiny 'dots' (divets ?) and the other side only has 3 near the center.
Marked on the rim is: "Registered Rockwell U.S. Pat. Off. and then a cursive "C" followed by 62.8 +/- 0.5.
How is this block used to test for steel or blade hardness ?
kj

[knife7knut]

Rockwell hardness testers use two scales for reference as I recall. The "B" which is not common and the "C" scale which is.The machine has a pointed tool that is pressed onto the test subject(in this case the disc)and the depth that the tool penetrates is read off an instrument.The harder the material the shallower the point will penetrate. The multiple punctures around the disc apparently were averaged and shows a pretty consistent hardness throughout. This is the calibration etched into the side of the disc.

[ea42]

The test block has a known hardness of 62.8 +/- so you would use the block to calibrate the machine. It has a dial reader so you would engage the machine on the block to calibrate the dial gauge to 62.8. Those holes are a result of a LOT of calibrations as well as the user testing the machine to see that it was still accurate. I used a Wilson similar to this quite often:

Eric

[kootenay joe]

Thank you Eric. Is the Rockwell testing instrument used to test the hardness of a few blades in every batch after heat treatment ? Or is every blade tested for hardness ?
If a blade was heat treated to say Rc 58 then when tested, the testing instrument should not be able to make a divot in the blade surface until the dial was set to higher than 58. Is this how it functioned ?
kj