In article ,
Don Bruder wrote:
[ ... Rockwell hardness tester operation ... ]
First off, just to be clear, I ain't the OP, just an interested
bystander with an observation/query about the item in question.
Correct me if I'm getting things cock-eyed, but...
This gizmo sounds to me like it's essentially a concept of "put in a
sample, work the lever to put a (presumably calibrated) amount of force
behind a hard (diamond?) point, then measure how deep the resulting dent
is and convert the depth to a rockwell number." Correct? Incorrect?
Somewhere in between?
Close -- with the addition of "first apply minor preload force
(with the vertical positioning screw) to set the zero, then work the
lever to apply gently apply the greater force, and return the lever to
remove the greater force, so you can measure how much deeper the diamond
is after the extra force.
I've got two different Rockwell hardness measuring devices. The
first is a portable hand-held device, and is a bit more awkward to use.
The second is a horizontal travel version. On both, there is a dial
indicator setting for the preload force, and a separate mechanism to
measure how far the diamond has moved after the cycle of increased
force. The preload is necessary to cut through surface crud and dust at
the start which could otherwise change your readings.
The first measures how far I turn the dial back to return to the
preload force level, while the second has an encoder on the leadscrew
(which drives the penetrator, not the specimen anvil) which drives an
LED numeric readout which is scaled according to which hardness scale is
selected on a rotary switch. IIRC, you apply the preload, hit a zeroing
switch, crank in the full load (different for different scales), then
crank it back out to the preload level, and read the hardness directly
on the LED readout.
I say this 'cause the discussion on preloading and zeroing the dials
sounds *A WHOLE BUNCH* like the setup for measuring runout on a shaft,
or brake rotor, or similar, using a machinist's dial indicator.
Similar -- except that the dial indicator is not intended to
deform the DUT (Device Under Test) in your shaft or brake rotor checking.
Part of the hardness test *requires* deforming the DUT. (I've seen
tools made for Bell System which had indentations from Rockwell hardness
measurements in multiple places.
I would suggest that the original poster get a hardness standard
somewhat near the expected range, and use it to check the calibration of
the tester. I've seen them offered on the same page of the MSC catalog
that sells hardness testers.
Enjoy,
DoN.
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