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<p>[QUOTE=&quot;cpm9ball, post: 1297805, member: 24633&quot;]True doubling occurs at a point when the design is being transferred from the hub to the die, and is sometimes referred to as hub doubling. Sometimes, the doubling occurs in the transfer from the master hub to the master die, and this doubling would be evident on all working hubs and dies. Most often, the doubling occurs in the transfer from the working hub to the working die.</p><p><br /></p><p>With that said, true hub doubling will create a secondary design image that has rounded devices and/or split serifs, whereas, machine doubling (also called mechanical doubling or strike doubling) will appear flat and shelf-like. If you look closely at most letters and numbers, you can see that the face (or top) of these are rounded, and it is this curvature that shows in a true doubled die. This rounded appearance can also be evident on doubled profiles where the device curves down to the field.</p><p><br /></p><p>Machine doubling occurs when a working die becomes loose in the retaining collar, and the vibration of the machinery causes it to &quot;chatter&quot; (move back and forth very rapidly). As the die withdraws from impact with the planchet, it scrapes across the surface of the planchet creating the flat, shelf-like secondary image of the device.</p><p><br /></p><p>Chris[/QUOTE]</p><p><br /></p>

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