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wrote:

I am curious just where the failures occurred when you used a heavy
press in.
Would it help if you made the hole for a heavy press fit at the bottom
of the hole and a lighter press fit toward the top of the hole.

Or how about grinding a very shallow groove about half a inch from the
end of the pin. Medium press fit with the groove inside the crs. Then
use a knurling tool with smooth knurls to press the crs into the
shallow groove.

Dan

Sorry...phone kept ringing and I was trying not to give so much
information as to limit responses..sometimes wild guesses can spark
inspiration. I also apologize if any of my responses have seemed abrupt
but It's been busy here the last couple of days.

The protruding pin has slight torque on it (impossible to calculate as
it's caused by spontaneous miss-alignments) and little tension (50
pounds worst case tension) if things are aligned properly. There is
also slight flexing. Every once in a while, the torque on the pin might
be higher but not so high that would count as high enough to pull things
apart on their own. What seems to be happening is related to the number
of cycles. Eventually, either the plug weld breaks off or in the case
of the press fits, things just eventually work to loosen the hole in the
rod so the pin eventually works itself out. Typical life is about 2
years and in that time, they see about 2 million cycles (quick calculation)

Unfortunately, even a very low failure rate can cause downtime on the
order of $ 10 grand an hour. It's clearly worth it to go high tech and
expensive to do it right but customers don't want to actually pay for
what they would be getting. This puts us in the corner of needing a
cheap solution about the equivalent of the plug-weld method on costs
while trying to get the results of finish ground induction hardened ends.

I believe that the better way to do it would be a heavy press fit with a
knurled pin AND mechanical fastening of some kind. I have to see if the
costs would work out though. .

Sooo...basically I was hoping that someone might have a novel solution
to send it in a different direction. The 1/2" rod does need to be cheap
mild steel and the pin needs one hell of a hard surface to reduce wear
and galling without becomming brittle at all.

Thanks to all those who answered

Koz