[Shop-talk] recommend a bolt

[Randall]

> Are there ratings on hitch pins
> that might tell me what'll be safe for sure? 

I didn't find anything in a brief check; but MMC shows hardness as only B80,
which
http://www.engineersedge.com/hardness_conversion.htm
says is roughly 73 kpsi steel.  That's significantly weaker than the Grade 5
bolt (120 kpsi) you had before (although the threads did take up some of
that).

I don't have a link, but I've read somewhere that shear strength is about
60% of tensile strength for carbon steel fasteners.  Proof (safe) load for a
5/8 Grade 5 in tension is just under 20k lbs, so shear would presumably be
about 12k.  Maybe double that, because your joint is in double shear?  That
might make a pin good for about 73/120 * 12k * 2 ~= 14k lbs.  Big question
then is how much do you multiply the weight of the car plus dolly for impact
loading (hitting bumps, car bouncing up and down); and then for safety
factor.  I dunno, but fixing things by making them weaker just doesn't seem
right to me.

One thought might be to use a stud, as they seem to have the unthreaded
length better specified:
http://www.mcmaster.com/#90281a816/=2iu8uc

Randall