Thingee, How-Did-That-Happen - Coin Community Forum

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Author	Replies: 5 / Views: 1,139
MorgansRmine Pillar of the Community United States 1219 Posts	Posted 01/14/2008 12:37 pm The scratches you refer to are die polishing lines. The face of a die starts as a flat piece of metal. The devices, lincolns profile, date, motto, etc are then engraved down into the surface at varying depths. The same way you would engrave a name on a trophy or an endearment on a piece of jewellery. This leaves the surounding area, fields, as the highest point on the die. When both dies strike each other with no coin inbetween, markings or clashes from the obverse are left on the reverse die and vice versa. These clashes are then polished away leaving polish lines engraved in the fields. Since the devices are sunken down into the die, the polishing procedure skips over the device and starts again on the next field. When the next coin is struck, the pressure genarates enough heat to melt the outer surface of the coin. This molton meltal flows into the devices and cools instantly as the dies separate leaving the raised devices and polishing lines. Hope this helps. Report this Post to the Staff

Jorgy Valued Member United States 145 Posts	Posted 01/14/2008 3:38 pm The only "Die" that is actually engraved is the mater hub. All other hubs and dies are made by squeezing the blank and hub together under a lot of pressure. Edited for spelling error. Edited by Jorgy 01/14/2008 3:43 pm Report this Post to the Staff
MorgansRmine Pillar of the Community United States 1219 Posts	Posted 01/14/2008 5:39 pm Your right. Should have specified that somewhere in my explanation. Report this Post to the Staff
foundinrolls Pillar of the Community United States 3507 Posts	Posted 01/15/2008 12:45 am There are several faults in that explanation and parts of the other, I am sorry to say. First, the diagnosis of the lines is actually correct. This is the effect of die polishing also called die dressing. It is often done to a die after two dies clash so that a die showing clash marks can continue in service. Just about everything else is out in the ether somewhere. A model of the coin around 15 inches in diameter is used by placing it on a Reducing Machine (Janvier Transfer reducing Machine). Its a lathe like thing that takes the design and puts it on the end of a piece of steel with the finished piece having the design on it the same size as a coin. This is the first Master Hub. Without going into all the metallurgy of the process, The Master Hub is used to make a Master Die. It is a hydraulic process whereby the Hub is pressed into a piece of steel to make the die. They then reverse this. They use a Master die to create a Working Hub. They make many Working Hubs. Again, pressure is used to press the master die into the rods used as hubs. The working hubs are then used to create working dies. Also, the shape of the tips of the rods used to create working dies are slightly conical and not flat. OK, now you have working dies in a press that just clashed. If it is caught, a technician removes the die, dresses it, creating those minute scratches , and at a later time loads it back into the press. Some of the coins will show the scratches. It is simply the immense pressure of the strikes that cause the lines to show up on coins as they are marks on the die. Eventually the pressure of subsequent strikes will obliterate the lines after awhile. Heat and molten metal plays no part in this. Thanks, Bill Edited by foundinrolls 01/15/2008 12:48 am Report this Post to the Staff
Metalman Pillar of the Community United States 7123 Posts	Posted 01/15/2008 02:31 am The minting process does not have to be a mystery . http://www.usmint.gov/mint_tours/in...tion=vtShell Report this Post to the Staff
thingee Pillar of the Community United States 2177 Posts	Posted 01/15/2008 9:17 pm Thanks for the thread MorgansRmine. I think I've got it now thanks to the posters! Report this Post to the Staff
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