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David David is offline
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Join Date: Apr 2002
Location: Houston (Clearlake), TX
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As for cast vs forged, I think a better description would be cast vs. wrought. Bolts are made of wrought bar stock that is hot rolled to produce the desired shape. So while they are not technically forged there has been some hot work performed on then. Also wrought materials are much cleaner, usually with a precise composition and very little non-metallic inclusions. Before additional work is done the material would be heat treated to the desired strength. Very high grade fasteners, like flywheel bolts I would assume, then have the threads rolled and the end forged to mushroom out the material for the head. Then the head is drilled and machined with a specially fixtured 5 sided cutter for a six point socket or the shape is EDM'd into the head.

In the US all SAE graded and most ASTM graded bolts must also have the manufacture's mark on the head. Even though it is required to use the markings there are many bolts around without them. Just last year I made our shop supplier take back hundreds of bolts that were not marked. I'm not sure if ISO has the same requirements, anyone know?
2014 Cayman S
2011 Cayenne Turbo
1979 930 (475 rwhp at 0.95 bar)
Old 06-30-2004, 04:32 PM
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