Rockwell B Scale is typically used with copper alloys. Table of Contents I have made a crude drawing in an attempt to illustrate this. This was authenticated as a Rockwell Test Mark by “Lonesome” John Devine. I believe that the reason for the difference in diameters is due to the effect of the strike on the indentation. He tested Rockwell 15T Scales. There are different scales, denoted by a single letter, that use different loads or indenters. (Materion Corporation, Page 1) Lincoln cents minted before 1982 have a thickness greater than 1.5 mm. In addition, a BB would most likely leave a pressure ridge around the circumference of the depression. There is always the chance that such a defect could be the result of a struck-in or rolled-in piece of debris that fell out after the strike. There should be no anvil effect (a raised area on the opposite side of the coin) and no pressure ridge around the circumference of the depression. According to my calculations, once the diameter of the mark exceeds approximately 0.28 mm, the slope of the sides will no longer be curved as they would be for a hemisphere, but will be straight and sloping outward at 120⁰ to reflect the shape of the cone portion of the indenter. Use of the C scale on Lincoln cents produces an anvil effect (a raised area on the opposite side of the coin) and leads to inaccurate Rockwell Number readings. “Because of the relatively small volume of material affected by the hardness test, care must be taken to obtain representative test data. “…the Rockwell test makes two depth measurements. Olin Kupferlegierungen “Copper Alloy Guide”. Hardness should be checked on cross sections when nonuniform cold work causes high surface hardness. “Dies and planchets tested in this fashion are supposed to be discarded, since they are blemished once the procedure is completed. As was observed in the 1971-S cent authenticated by John Devine, the diameter of the indentation may be slightly smaller than the indentation on the reference coin, due to some “closing up” during the strike. Is there a way to search all eBay sites for different countries at once? If they are not discarded, then you have a desirable die error and planchet error, respectively.” (Diamond, Page 16). The copper alloy used in pre-1982 cents is 45 on the Rockwell B Scale. But when we are dealing with Jewelry, most people are more familiar with the … A Rockwell Test Mark should have a smooth, hemispherical cross section profile and assume the shape of a circle or an oval (if it is adjacent to a device). Elsewhere I have read that such errors are largely or exclusively restricted to S-mintmark cents from the early 1970’s (I can no longer remember the source, however).” (Diamond Page 17; Steiner and Zimpfer, pp. How long does a fresh turkey last in the refrigerator? Hard materisl resist wear and scratches. When you go to the Die Variety Master listing link above you will be redirected to the CONECA information files hosted on Dr. James Wiles Variety Vista website. I have attempted to take these ideas seriously and have come to the realization that a critical piece of information in considering each possibility is the nature of the geometry of the tips of these instruments. It would be even more improbable for all these things to occur twice on the same coin as the result of random post-mint contact, as appears on this 1995-D. On the other hand, Rockwell Testing Protocol does suggest that an object be tested at least twice so the results can be averaged. The Rockwell Scale was invented in 1908 by two men, Hugh Rockwell and Stanley Rockwell (no relation). At the time they wrote their book, Steiner and Zimpfer (1975) recognized such errors as the exclusive output of the San Francisco Mint. But when we are dealing with Jewelry, most people are more familiar with the Moh’s Scale. The depth of penetration of the indenter must be less than 10% of the metal thickness, and the reading must be taken at least two indenter diameters from an edge.” (Materion Corporation, 9/4/2015). In Figure 2, it can be seen that the indentation on the 2000-D cent is slightly larger and deeper than the indentation on the 1976-D cent. Why don't libraries smell like bookstores? I know of no way to calculate the probability of all those things occurring as a result of random post-mint damage – but I think it would be astronomical. I would also add that there must be no bulge on the opposite face. It may also leave an anvil effect (raised area) on the opposite side of the coin. The most we can say is that a particular indentation meets the expectations of a Rockwell Test Mark. If this response from the Mint is correct, then it is improbable that the indentation in the 1971-S cent is a Rockwell Test Mark. The depth of the mark is what translates into the hardness number and also what translates into the diameter of the mark. It is equal to the magnitude of the force exerted by 1 kilogram of mass in the average magnitude of gravity on earth). (Concurrent Technologies Corporation, Page 42) The actual value on this 2000-D was measured at 59.1. When did organ music become associated with baseball? If you use anything there that ends in index.html it will take you to this site, but to a 404 error page. Rockwell hardness test into what is today the most widely used method for acceptance testing and process control of metals and metal products. Using various metal working processes, this alloy is capable of being hardened to 64 RHC. Metal Hardness is usually defined by the Rockwell Hardness Test. This might cause a certain confusion, because sometimes a hardness of the HRC scale is ordered, although the small dimensions of the sample make tests with a total test load of 1471 N impossible. This same source shows a photo of a 2000 Lincoln Cent with a small, circular indentation just above Lincoln’s bow tie. Metals aren’t really tested with the Moh’s Scale of Hardness, they are actually, and more accurately, tested with the Rockwell Scale of Hardness. I have done a few calculations to try to see what a BB strike would need to look like. Coin Digest, 11th Edition, (Krause Publications). (Jardin Zinc Sales 8/14/2015). This description provides a working definition of how a Rockwell Test Mark in planchet is to be recognized. Even if it were from a Rockwell Test such an “anvil effect” would indicate that too much pressure had been used and the resulting Rockwell Number would likely be inaccurate. (Dusharme, 9/2/2015; Low Page, 13) The actual 15T Rockwell Hardness on this 1976D was measured at 75.2 (Figure2). The steel alloys are Alloy 52100 for small diameter coins and Alloy L6 for quarter on up. One is a 2000-D Lincoln Memorial Cent with one indentation on the reverse (Figure 5). Absolute certainty requires that the test itself be witnessed and the planchet followed through the complete minting process! Hardness of any material is tested by various method like Rockwell hardness test,Brinell hardness test etc. Annealed silver steel has a hardness of 27 on the Rockwell scale of hardness (RHC). Notes on the Vickers Hardness of particular elements: Silicon: converted from Mohs scale Germanium: converted from Mohs scale Arsenic: converted from Brinell scale Ruthenium: converted from Brinell scale Osmium: converted from Brinell scale Up to date, curated data provided by Mathematica's ElementData function from Wolfram Research, Inc. Silver steel products may feature different levels of hardness, depending on how much carbon they contain and how they are manufactured. (Latrobe, 52100), Alloy L6 is a versatile oil-hardening tool steel that is characterized by good toughness and is suitable for tools, dies and machine parts. (US Mint, E-mail 8/24/2015, Diamond, 2006, Page 16). Its typical composition is 0.70 C, 0.60 Mn, 0.25 Si, 0.70 Cr, 1.40 Ni, and the balance Fe. Annealed silver steel has a hardness of 27 on the Rockwell scale of hardness (RHC).
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