Hi All, I've gotten a Rockwell hardness tester without instructions. It seems to be so simple but I'm having trouble figuring out how to use it. From what I've found in web searches it seems that there should be a "minor" load applied and then the "major" load applied by the weights and then back to the "minor" load to take the reading. I'm not exactly sure how to apply the "minor" load on my machine. I can turn the base screw to apply some preload but that hardly seems exact. If anyone has used a machine similar to this one and could describe the process I'd appreciate it.
There is a handle on the lower right hand side of the frame of the tester...roll it towards you...that will raise the load weight.
Set your pre-load so that the hand in the small dial is pretty well centered on the dot. Do this with the big screw that your sample table is sitting on top of. Then turn the outer dial until the dial is zeroed.
Now gently push that preload handle away from you and it'll go the rest of the way by itself...when it stops, gently roll it back towards you and read your value from the dial.
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 c*ck-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?
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.
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.
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.
Mi capiche. I simply forgot to include the "zero" step as I was typing.
Right, but that wasn't the point - The post I was responding to made it sound a *WHOLE LOT* like setup/use of a dial-indicator for runout checking. I'm quite aware that the indicator doesn't dent the test item, or even make an attempt to.
The "sounds like using a dial indicator" idea sparked a train of thought that derailed into how the hardness tester might be generating its reading, causing a major spill of "I think it might work like this, let's ask and see if I'm crazy, brilliant, or somewhere in between" :)
Put the pice to be tested on the anvil rase the pice to be tested until it almost macks contact with the diamond Watch the small needle and rase the pice to be tested so the small needle TURNS 3 TIMES and stops on the dot.This is your 10 kg load . Turn the outside of large dial to read 0 with the big needle , now turn the handle to let the weights down this is your 150 kg load .the 150 kg load should come down very slow there is a pistion with oil in it you can adjust how fast the 150 kg load comes down.Watch the big needle untill it stops .Now turn the handle to take the 150 kg load off . The reading on the big needle it your hardness number.
Thanks for all the help. I think I'm getting somewhat accurate readings now. I took some pictures of the process I used tonight if anyone wants to see them. First a picture of the penetrator I'm using - it doesn't actually say "Brale" on it so I hope it's really a Brale tip.
A chart showing different weights to use for different tips
The process I used: I first used the screw base to push the sample up into the penetrator until the needle made 3 revolutions. According to advice given here that should be the 10Kg preload. I zeroed the dial on the "C" scale
I then applied the 150kG load and the dial made about 1.25 revolutions counter-clockwise
I then removed the 150kg load and the needle swung clockwise to the reading.
This appears to indicate a hardness of 24 Rockwell C. I tried it several times in several spots and got similar readings. I thought the piece of steel I was using was prehardened 4140 which I expected to be closer to
35 but now I'm not totally sure if it was hardened or annealed.
At any rate I think I just need to get samples of different hardnesses and try them. This will certainly be adequate for my hobby endeavors. Thanks for the help.