"Gary Warner" wrote in message ...
Finally, a thread about threads.

Silly question but just for discussion sake: I am bolting some safety chains
to our home-made trailer. Eventually they will be weled on as well as bolted
but for now (long story) we just want to bolt them.

So I got a 4" bolt in "Grade 8" hardened steel. But they come in both
course and fine thread. I went for the course thread. Question: Is there
any functional difference or reason to choose a course versus a fine
thread for this type (or other) applications??

If in tension or compression, the fine thread bolt will be superior to
the coarse thread, because there is more surface area. If it is in
shear, then, without thinking too much about it, I'd guess that the
fine thread would win again, because I think fine threads aren't cut
as deep as coarse.