It is apparent that the 2026-P Dimes exhibit a number of minor die cracks, breaks, and ripples concentrated in the area below the base of Lady Liberty's neck. The frequency of these occurrences is high, as any search of sale venues will attest. WHY IS THAT? The answer is fascinating and is grounded in the history of die design for the production of designs that allow for effective coinability, striking efficiency, and cost-conscious production. Since 1836, the shape of a coin die face has been a critical element in the mintage of coins. The mint was having difficulty striking coins because the dies were flat and kept cracking and forming Cuds. They quickly learned that the die face needed to be of a convex shape to extend die life and reduce striking pressure. A basic principle of coin die design for acceptable coinability is that design relief height determines die curvature. A higher relief requires a higher (deeper) curvature in order to facilitate metal flow into deeper areas of the die during striking as well as stackability during circulation. Until modern times with the arrival of CNC (Computer Numerical Controlled) Milling Machines, production methods required die curvature to be a constant radius with a spherical curvature. (The surface of a die may be thought of as a tiny spot of the surface of a large ball). With CNC, the mint gained the ability to design variable curvatures. Both Exponential and Spherical curvatures are now possible. (See image below) They may even exist on the same coin and have the ability to merge gradually one into the other. Such is the case on the 2026-P Dime. On the 2026-P Dime, the base of the neck is close to the highest relief of the design: 1,368.29µm = only 12.93µm less than the peak relief of the design as measured by a profile scan. This means that the field curvature must be deeper in this area than adjacent (3mm) areas with a lower relief (by about 90µm and 2° to 4° less curvature slope) in order to accommodate that relief. The difference in relief heights and curvature profiles creates a channel on the coin extending from the base of the neck towards the edge of the coin. The net result is a localized zone of stress concentration on the die. Unlike a spherical die face, the pressure of an exponential curvature during the strike does not increase uniformly with radius. It starts gradually at the center of the die, accelerates slowly at first, then accelerates more rapidly beginning at the point where the curvature begins to steepen more rapidly (red arrow in the cross-sectional graph below). The stress concentration is further accentuated by additional pressure vectors caused by the isolation of the zone by the adjacent, shallower, curvatures already mentioned. The zone becomes the area where so many minor die cracks, breaks, and ripples have been found. Background information may be found in this link and additional research is in progress. Stay Tuned! https://coinweek.com/coin-die-desig...d-the-2026-p-dime-break-a-100-year-mint-rule/
So, if I understand correctly, the advanced technology of today allows them to contour the face of a die with greater control and precision than ever before. And they came up with a design that is more prone to cracking?
