Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work.

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Kris
 
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Default How to use an old Rockwell hardness tester

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.

pics at:
http://www.personal.psu.edu/kjm182/pics/hardtester/dial.jpg
http://www.personal.psu.edu/kjm182/pics/hardtester/overall.jpg
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The Davenport's
 
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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.

pics at:
http://www.personal.psu.edu/kjm182/pics/hardtester/dial.jpg
http://www.personal.psu.edu/kjm182/pics/hardtester/overall.jpg


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.

Done.

Luck

Mike


  #3   Report Post  
Don Bruder
 
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In article ,
"The Davenport's" wrote:

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.

pics at:
http://www.personal.psu.edu/kjm182/pics/hardtester/dial.jpg
http://www.personal.psu.edu/kjm182/pics/hardtester/overall.jpg


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.

Done.


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?

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.

--
Don Bruder - - New Email policy in effect as of Feb. 21, 2004.
Short form: I'm trashing EVERY E-mail that doesn't contain a password in the
subject unless it comes from a "whitelisted" (pre-approved by me) address.
See http://www.sonic.net/~dakidd/main/contact.html for full details.
  #4   Report Post  
DoN. Nichols
 
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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.
--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---
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Don Bruder
 
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In article ,
(DoN. Nichols) wrote:

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.


Mi capiche. I simply forgot to include the "zero" step as I was typing.

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.


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"

--
Don Bruder -
- New Email policy in effect as of Feb. 21, 2004.
Short form: I'm trashing EVERY E-mail that doesn't contain a password in the
subject unless it comes from a "whitelisted" (pre-approved by me) address.
See http://www.sonic.net/~dakidd/main/contact.html for full details.


  #6   Report Post  
tim
 
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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.

  #7   Report Post  
Kris
 
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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.

http://www.personal.psu.edu/kjm182/pics/hardtester/penetrator.jpg

A chart showing different weights to use for different tips

http://www.personal.psu.edu/kjm182/pics/hardtester/chart.jpg

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

http://www.personal.psu.edu/kjm182/pics/hardtester/step1.jpg

I then applied the 150kG load and the dial made about 1.25 revolutions
counter-clockwise

http://www.personal.psu.edu/kjm182/pics/hardtester/step2.jpg

I then removed the 150kg load and the needle swung clockwise to the reading.

http://www.personal.psu.edu/kjm182/pics/hardtester/step3.jpg

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.

-Kris

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D Murphy
 
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Kris wrote in :

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.


I see Rockwell calibration standards on ebay all the time. They go for
short money compared to new.


--

Dan

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