"AL" wrote in message news:%p59c.13948$JO3.22918@attbi_s04...
I believe, but am not 100% sure, that a chain rated for overhead lifting
has
a greater safety margin and is designed to fail somewhat gracefully. For
example, a regular chain rated for 1000 pounds may actually be designed
for
2000 pounds. A overhead lifting chain rated for 1000 pounds may be
designed
for 4000 pounds.

At work we constantly lift dies that weight up to about 70 metric tonnes
(about 155,000lbs) using cranes with chains. We also have to flip these
dies. Sometimes they get stuck on the chains as they are crossing their
*apex*. At some point, the chain will get out of the die's way and the die
drops. It's quite a sound when a die bounces on those chains. Scary too. I
don't think we've ever hard a chain fail (the links are made of about 3/4"
diameter material, IIRC).

I'd say there's a bit of a safety factor built in ;-)

Regards,

Robin