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#1
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Polishing lines?
Are there supposed to be polishing lines on DMPL Morgan dollars?I've seen
two so far that have them. One is slabbed by PCI,the other is raw. |
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#2
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Polishing lines?
On Nov 26, 7:07�pm, "don't look" don't wrote:
Are there supposed to be polishing lines on DMPL Morgan dollars?I've seen two so far that have them. One is slabbed by PCI,the other is raw. There are many questions posed in this newsgroup that require a bit more specificity when asked. Questions about cleaning coins are one example. Your question is another. Are you talking about hairlines from polishing or the raised lines you may see on some coins as a result of die polishing at the Mint? The hairlines are a no-no while the lines from die polishing are ok, although some may consider them to be undesireable. Since PCI has changed hands a few times, using them as an example also requires a bit more specificity. The original PCI is somewhat highly regarded by many while the more recent incarnations are not. |
#3
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Polishing lines?
"Phil DeMayo" wrote in message ... On Nov 26, 7:07?pm, "don't look" don't wrote: Are there supposed to be polishing lines on DMPL Morgan dollars?I've seen two so far that have them. One is slabbed by PCI,the other is raw. There are many questions posed in this newsgroup that require a bit more specificity when asked. Questions about cleaning coins are one example. Your question is another. Are you talking about hairlines from polishing or the raised lines you may see on some coins as a result of die polishing at the Mint? The hairlines are a no-no while the lines from die polishing are ok, although some may consider them to be undesireable. Since PCI has changed hands a few times, using them as an example also requires a bit more specificity. The original PCI is somewhat highly regarded by many while the more recent incarnations are not. Thanks for your answer. So,you are saying that there is such a thing as polishing lines from a die? They are not like any cleaning lines I've seen. They all go the same way.The lines also are not really visible in the devices.Only the fields.If they had been cleaned,most of the frost would be gone as well? |
#4
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Polishing lines?
On Nov 26, 9:42�pm, "don't look" don't wrote:
Thanks for your answer. So,you are saying that there is such a thing as polishing lines from a die? They are not like any cleaning lines I've seen. They all go the same way.The lines also are not really visible in the devices.Only the fields.If they had been cleaned,most of the frost would be gone as well? Sounds like die polishing lines to me. From what I understand the surface of the die would be wiped with a polishing cloth. This would leave parallel striations in the surface of the die, but only in the fields since the devices are recessed on the die. The die polishing lines would then be transferred to the surface of the coin during striking, If the lines you see are raised from the surface of the coin, that would confirm the diagnosis. |
#5
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Polishing lines?
"Phil DeMayo" wrote in message ... On Nov 26, 9:42?pm, "don't look" don't wrote: Thanks for your answer. So,you are saying that there is such a thing as polishing lines from a die? They are not like any cleaning lines I've seen. They all go the same way.The lines also are not really visible in the devices.Only the fields.If they had been cleaned,most of the frost would be gone as well? Sounds like die polishing lines to me. From what I understand the surface of the die would be wiped with a polishing cloth. This would leave parallel striations in the surface of the die, but only in the fields since the devices are recessed on the die. The die polishing lines would then be transferred to the surface of the coin during striking, If the lines you see are raised from the surface of the coin, that would confirm the diagnosis. All quite accurate, but it raises another question: What kind of "polishing cloth" would be abrasive enough to cut grooves into the hardened die steel? Crocus cloth comes to mind, but I really have no idea whether something like that is used. Do you? James |
#6
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Polishing lines?
"Mr. Jaggers" lugburzman[at]yahoo[dot]com wrote in message ... "Phil DeMayo" wrote in message ... On Nov 26, 9:42?pm, "don't look" don't wrote: Thanks for your answer. So,you are saying that there is such a thing as polishing lines from a die? They are not like any cleaning lines I've seen. They all go the same way.The lines also are not really visible in the devices.Only the fields.If they had been cleaned,most of the frost would be gone as well? Sounds like die polishing lines to me. From what I understand the surface of the die would be wiped with a polishing cloth. This would leave parallel striations in the surface of the die, but only in the fields since the devices are recessed on the die. The die polishing lines would then be transferred to the surface of the coin during striking, If the lines you see are raised from the surface of the coin, that would confirm the diagnosis. All quite accurate, but it raises another question: What kind of "polishing cloth" would be abrasive enough to cut grooves into the hardened die steel? Crocus cloth comes to mind, but I really have no idea whether something like that is used. Do you? James Now I know what to look for and using a 15x magnifier, I looked at my PL Morgans and those have them too,though not quite as visible as in the deep mirrored morgans. I've really never looked that closely until recently. It's really hard to tell if ther lines are raised. They are just too small. But, I can see them in tiny , tiny areas that would be almost impossible to reach if it was done after. Hmm, intersting stuff. I think any kind of polishing cloth run across a mirror-like object, in this case a die pair, would leave lines behind. Kind of like trying to polish chrome. You can't touch it with a cloth and not make marks. |
#7
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Polishing lines?
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#8
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Polishing lines?
On Nov 26, 10:56�pm, "Mr. Jaggers" lugburzman[at]yahoo[dot]com
wrote: All quite accurate, but it raises another question: �What kind of "polishing cloth" would be abrasive enough to cut grooves into the hardened die steel? Crocus cloth comes to mind, but I really have no idea whether something like that is used. �Do you? James When compared to the minerals that might be used in polishing compounds, steel isn't all that hard. The most common abrasive would probably be corundum (aluminum oxide) which has a Mohs scale hardness of 9 (second only to diamond at 10). The average woman probably has some corundum in her purse (an emery board). You might have some aluminum oxide sandpaper in your workshop. In addition to emery, the corundum family includes sapphires and rubies. I have a jar of ruby powder somewhere around here that I used to polish some minerals and gemstones that I cut (mostly Opals and Mexican Fire Opals). I also used a few different grades of diamond compound on harder minerals. |
#9
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Polishing lines?
"Phil DeMayo" wrote in message ... On Nov 26, 10:56?pm, "Mr. Jaggers" lugburzman[at]yahoo[dot]com wrote: All quite accurate, but it raises another question: ?What kind of "polishing cloth" would be abrasive enough to cut grooves into the hardened die steel? Crocus cloth comes to mind, but I really have no idea whether something like that is used. ?Do you? James When compared to the minerals that might be used in polishing compounds, steel isn't all that hard. The most common abrasive would probably be corundum (aluminum oxide) which has a Mohs scale hardness of 9 (second only to diamond at 10). The average woman probably has some corundum in her purse (an emery board). You might have some aluminum oxide sandpaper in your workshop. In addition to emery, the corundum family includes sapphires and rubies. I have a jar of ruby powder somewhere around here that I used to polish some minerals and gemstones that I cut (mostly Opals and Mexican Fire Opals). I also used a few different grades of diamond compound on harder minerals. - But how are these abrasives "delivered" to the die steel? Are they in a paste rubbed on with a rag, or what? And don't they (or at least shouldn't they) progress through a series of ever-finer abrasives to smooth out the scoring caused by the one before? I'm thinking it's like grinding a mirror for a telescope, is there an analogy there? James |
#10
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Polishing lines?
On Nov 27, 5:20�am, "Mr. Jaggers" lugburzman[at]yahoo[dot]com wrote:
- But how are these abrasives "delivered" to the die steel? �Are they in a paste rubbed on with a rag, or what? �And don't they (or at least shouldn't they) progress through a series of ever-finer abrasives to smooth out the scoring caused by the one before? �I'm thinking it's like grinding a mirror for a telescope, is there an analogy there? James I imagine that normal die refinishing is done at the Mint by qualified employees using the proper equipment, including an increasingly finer series of abrasive polishing compounds. I also imagine, that the few and far between dies that bear "polishing lines" are not the result of standard refinishing. More likely (speculation here) they are the result of a floor employee noticing some grease or other foreign substance on the surface of a die, grabbing the closest rag and wiping the die clean. One can only imagine what is contained in the grease/debris or on the rag. Notice the three uses of the word "imagine". ;-) |
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