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<p>[QUOTE=&quot;Kasia, post: 2057481, member: 31533&quot;]Regarding die sink problems on the Ike, the Ike group has a page that has this on that (talking about 1971-1972 coins), so presumably the steel issue of the die was taken care of by 1975 or 1976 for this coin (found under <b>Metallurgy of Ike Dollars</b>).:</p><p>&quot;However, as hardenable steel, it is very important to know that W-1 does not through-harden.&nbsp; What does that mean? The outer surfaces in contact with the quenching medium will achieve the most martensitic structure and hence the highest hardness, toughness, etc.&nbsp; For example, if one were to cut through a W-1 die, the hardness readings of the steel decreases as one moves towards the center of the die’s cross sectional thickness.&nbsp; This is due to the fact that the inner cross section of metal does not come in direct contact with the quenching media and therefore can‘t quench fast enough to completely transform the soft austenite to martensite. The inner areas end up retaining an austenite phase in the metal matrix.&nbsp; This condition allows for a small degree of plasticity of the die when striking the planchet, and could easily lead to what was known as die-sink.</p><p>Die-sink occurs when the dies deform to a very small degree as opposed to remaining completely rigid when contacting the planchet under full pressure. Relatively speaking, the softer inner areas of the die were allowing a fair amount of plasticity of the central die face as compared to remaining rigid as a more through-hardenable tool steel would perform.&nbsp; Die sink from the operating strength of the W-1 tool steel was not allowing the mint to get coins that were fully struck up on the 1971 through July 1972 Ikes, thus necessitating a low relief design for the business strikes. The die sink phenomena lead the mint to search for a better tool steel to strike the large Eisenhower dollars.&quot;</p><p><br /></p><p>.....</p><p>But that is not to say that one die, or even a die set could not have a problem that left the inner areas retaining one phase and the outer areas having another. If this is the cause.</p><p><br /></p><p>Would love to hear more, because it would help me learn more about this.[/QUOTE]</p><p><br /></p>

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