In a few previous posts I have referred to the subject of correct edging methods. Some time ago I made up a sketch of the process to explain it to a friend. I just found the sketch while cleaning out old pictures and thought it might help to explain what happened.
In the days of the open sided screw press (before 1836 in the US and before 1897 in Mexico) the edge design on a coin was applied in a separate step from the strike. The apparatus used to edge a coin blank - illustrated in "Hooknecks" by Hubbard and O'Harrow is straight forward. Two flat bar dies that both have the edge design are mounted parallel on the surface of the milling machine. One die is movable one is Fixed. The raw blank fits in between them. The movable die is cranked toward the fixed die squeezing the blank and imparting the design. Then the movable die is moved along parallel to the fixed die adding the design to the opposite sides of the blank at the same time. When the blank rolls 1/2 way around the whole thing has been edged and the pressure is released. The blank is a bit smaller in diameter and it has become a planchet with upset rims ready to strike.
The geometry of the apparatus means that what happens on one side has an effect on the opposite side. When getting to the end of the process - TWO OVERLAPS are created exactly opposite one another of the SAME length.
But if one side pops out of the edger - the other side shows the effect as well. If there is a clip on one side - the opposite side would not get edged as well. Think through what happens using a coin and two rulers - you should get the picture.
Here is the sketch. If I can find a copy of the actual apparatus in my files I will add it.
Image: 
Edger jpeg.jpg79.74 KB
Posted 08/11/2006 11:02 am
Edger jpeg.jpg
