Rockwell Hardness Test

Anyone here know anything about this test? There is a Jefferson Nickel that
dates 1946- D that has this test done to it. The following is all I know
about it.


ALAN HERBERT IN HIS MONUMENTAL WORK "PRICE GUIDE TO MINT ERRORS" PUBLISHED
IN 2002 DESCRIBES A HARDNESS-TEST-MARKED PLANCHET AS "A PLANCHET WITH A
SMALL ROUND CIRCULAR IMPRESSION OR INDENTATION RESULTING FROM THE PRESSING
OF A SMALL ROUND TEST PROBE INTO THE METAL TO TEST THE HARDNESS OF THE
PLANCHET."

HERBERT GOES ON TO GIVE THIS TEST A RARITY LEVEL OF "UNKNOWN" -- UP UNTIL
2002 (DATE OF PUBLICATION) NO CONFIRMED REPORT HAD BEEN VERIFIED. BUT THIS
5 CENT PIECE IS DATED 1946 LENDING CREDENCE THAT THIS TEST HAS BEEN USED FOR
OVER 50 YEARS AND IS A UNIQUE ERROR/VARIETY!


Anyone else know anything about this test?

Thanks, Fred

Anyone here know anything about this test? There is a Jefferson Nickel that
dates 1946- D that has this test done to it. The following is all I know
about it.


ALAN HERBERT IN HIS MONUMENTAL WORK "PRICE GUIDE TO MINT ERRORS" PUBLISHED
IN 2002 DESCRIBES A HARDNESS-TEST-MARKED PLANCHET AS "A PLANCHET WITH A
SMALL ROUND CIRCULAR IMPRESSION OR INDENTATION RESULTING FROM THE PRESSING
OF A SMALL ROUND TEST PROBE INTO THE METAL TO TEST THE HARDNESS OF THE
PLANCHET."

HERBERT GOES ON TO GIVE THIS TEST A RARITY LEVEL OF "UNKNOWN" -- UP UNTIL
2002 (DATE OF PUBLICATION) NO CONFIRMED REPORT HAD BEEN VERIFIED. BUT THIS
5 CENT PIECE IS DATED 1946 LENDING CREDENCE THAT THIS TEST HAS BEEN USED FOR
OVER 50 YEARS AND IS A UNIQUE ERROR/VARIETY!


Anyone else know anything about this test?

Thanks, Fred



It's a method of testing hardness that has been around since the 20's.
It's a diamond tipped tool with a 120 deg. cone and a .008" radius on the tip.
The machine measures how deep the tip goes into the metal under a set weight.
That is why it leaves a small round indentation into the metal being tested.

Bill

Subject: Rockwell Hardness Test
From: "Fred"
Date: 12/7/03 9:07 AM Central Standard

Anyone here know anything about this test? There is a Jefferson Nickel that
dates 1946- D that has this test done to it.
Thanks, Fred

Rockwell hardness tests can be performed on a die, a blank, a planchet, or a
finished coin. If done on a die, there will be a raised, circular bump on a
coin. I know of only one claimed example of a Rockwell test on a die, this a
1980 cent. There's a circular raised dot in the loop of the 9. It's a dubious
example in my opinion. Although it's clearly not a die chip, its location is
not where you'd expect a Rockwell test to be applied.

Rockwell tests on planchets are mainly known from Lincoln cents from the early
1970s, San Francisco mint. I have one in a 1971-S cent authenticated by
Lonesome John Devine. It looks convincing to me. Slightly out-of-round as a
result of the strike, with no pressure ridge on the border and no damage to the
opposite face.

They are very difficult errors to authenticate and require examination under
high magnification.


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Anyone else know anything about this test?

Thanks, Fred


http://www.mee-inc.com/rockhar.html

To greatly simplify the rockwell test, you hit the material with a
calibrated punch. You then determine the hardness of the material by
how deep the punch went.

hey - check out the following scan of a 1932 eagle I have - I always wondered
what the circular indentation at 3:00 was - any chance this is the result of a
hardness test (BTW, I always thought that most hardness tests used a
diamond-shaped punch)?

http://members.aol.com/dnakornreich/1932eagleo.jpg

FYI, sent this in to ANACS - came back net AU58 for cleaning - no mention of
the mark at 3:00.
-drew

"David Hamilton" wrote in message
...



Anyone else know anything about this test?

Thanks, Fred


http://www.mee-inc.com/rockhar.html

To greatly simplify the rockwell test, you hit the material with a
calibrated punch. You then determine the hardness of the material by
how deep the punch went.

Should not the hit be calibrated also ? All of the hard parts of US military
firearms have a ding on them. Each one is tested separately, every time.

Rockwell tests are among the most common methods of determining
hardness of metals. They are popular among engineers and metallurgists
because hardness is cheap and easy to test, yet affords good insight
into harder-to-test properties, like chemical resistance, tensile
strength, etc.

Presumably the Mint and/or its suppliers test some (very small)
fraction of planchets as part of their quality control procedures. If
the test is performed before the coin is struck, I would expect the
"dimple" to be altered in the minting process, perhaps the point of
obscurity (less-so with today's low-relief coins). If it's done
afterwards, an expert could probably easily recognize such a mark, but
I don't know how you'd tell the difference between a Mint-originated
dimple and one created by anyone else with access to a Rockwell tester
(and there are lots of us).

I can understand why the rarity of such pieces would be unknown.

--Chris S

"Fred" wrote:
Anyone here know anything about this test? There is a Jefferson Nickel that
dates 1946- D that has this test done to it. The following is all I know
about it.


ALAN HERBERT IN HIS MONUMENTAL WORK "PRICE GUIDE TO MINT ERRORS" PUBLISHED
IN 2002 DESCRIBES A HARDNESS-TEST-MARKED PLANCHET AS "A PLANCHET WITH A
SMALL ROUND CIRCULAR IMPRESSION OR INDENTATION RESULTING FROM THE PRESSING
OF A SMALL ROUND TEST PROBE INTO THE METAL TO TEST THE HARDNESS OF THE
PLANCHET."

HERBERT GOES ON TO GIVE THIS TEST A RARITY LEVEL OF "UNKNOWN" -- UP UNTIL
2002 (DATE OF PUBLICATION) NO CONFIRMED REPORT HAD BEEN VERIFIED. BUT THIS
5 CENT PIECE IS DATED 1946 LENDING CREDENCE THAT THIS TEST HAS BEEN USED FOR
OVER 50 YEARS AND IS A UNIQUE ERROR/VARIETY!


Anyone else know anything about this test?

From:

hey - check out the following scan of a 1932 eagle I have - I always wondered
what the circular indentation at 3:00 was - any chance this is the result of
a
hardness test (BTW, I always thought that most hardness tests used a
diamond-shaped punch)?


Could be. Hardness tests on soft metal is done with an indentor tipped
with a carbide ball, rather than a diamond cone.

Bill

Subject: Rockwell Hardness Test
From: (Dnakornreich)
Date: 12/7/03 1:19 PM Central Standard Time
Message-id:

hey - check out the following scan of a 1932 eagle I have - I always wondered
what the circular indentation at 3:00 was - any chance this is the result of
a
hardness test?

It looks too irregular and too shallow to me. Probably just a stike-through
error.

Host: Error Coin Information Exchange (Yahoo:Groups); CONECA #2969.
My opinions do not necessarily reflect those held by any organization I am a
member of..

"Dnakornreich" wrote in message
...
hey - check out the following scan of a 1932 eagle I have - I always
wondered
what the circular indentation at 3:00 was - any chance this is the result
of a
hardness test (BTW, I always thought that most hardness tests used a
diamond-shaped punch)?

http://members.aol.com/dnakornreich/1932eagleo.jpg

FYI, sent this in to ANACS - came back net AU58 for cleaning - no mention
of
the mark at 3:00.
-drew


I've done hundreds of Rockwell hardness tests on ferrous and non-ferrous
metal samples, and that dint looks about right. It is hemi-spherical, isn't
it? Gold would be tested with a ball tester, not a point.

Looks like its copped a fair bit of circulation since the test.

Hehehe. Rockwell testing dents - the chopmarks of the modern era.