[Land-speed] Dumb Question # 4857 - Wrist Pin Diameters

[Kirkwood]

These were designed in the days long before FEA. The accepted method was to
start oversize, as Mark has said, and then continue reducing size along with
tensile testing until the breaking strength is at an acceptable level. The
other thing to consider is the OEM's subcontractor's existing tooling. As Ed
mentioned cost was, and still is, the driver. If you are making 40 million
pins a year you must consider the total cost to make small changes to a
multi-million dollar transfer line or process. The size was probably the
most economical result of changes to existing tooling. 40 million pins
(3.75" length) is about 2,400 miles of bar stock. At that volume the factory
can get whatever nominal size it wants directly from the mill without cost
penalty. However, material costs savings still result with smaller
diameters. As Ed indicated, one penny less in material cost is about
$400,000.

From: Larry Mayfield <drmayf at mayfco.com>
(snip . . . ) fords is 0.912 inches and GM's is 0.927.  Why the odd
dimension used?