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<p>[QUOTE=&quot;Tom Maringer, post: 182716, member: 7033&quot;]<b>How much pressure to burst a collar?</b></p><p><br /></p><p>Well... it SHOULDN&#039;T have burst. The hydraulic up-acting coining presses like this one have the striking pressure adjustable by means of a dial. I was running the press at 150 tons. I have struck coins in collars up to 250 tons on this same press before without breaking one. On close examination of the fractures and on consulting the handbook TOOL STEEL TROUBLESHOOTING I believe that in this case I the problem was in the heat-treatment... an inadequate tempering of the steel after hardening left it too hard and brittle for the collar. I had heat-treated the collar along with a number of dies at the same time. While dies need to be as hard as possible... it&#039;s more important for a collar to be tough. Therefore I should have tempered the collar separately from the dies and at a higher temperature. I&#039;m just glad I&#039;m still around to have learned this lesson.</p><p><br /></p><p>No heat though... the coins get hot from the metal flow when striking... but there was no heat generated in the fracture of the steel... all the energy went into propagating the crack(s).[/QUOTE]</p><p><br /></p>

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