[TR] Differences between a bolt - hexagon head and a setscrew - hexagon head

[Randall]

> By the way,  i have noticed what in the USA is called a hex 
> cap screw. "A hex head cap screw is a six-sided bolt with a 
> trimmed hex head and a washer face on the bearing surface" 

The terminology is not always used consistently even within the US.  The
term "cap screw" is sometimes used only as the opposite of "set screw",
indicating that it does have a head that is larger than the threads.
Another definition is that a "cap screw" threads into some other part (like
a manifold or cylinder head) rather than a "bolt" going into a nut.

> Most of my screws and bolts for the Triumph  have this washer 
> face. Do I really need an additional washer or is the washer 
> needed to spread the load?

Depends on the application; but in general if the manufacturer specified a
flat washer, then I would use one.  I've found several places where adding a
flat washer helped significantly; can't remember ever thinking that leaving
one out would help in any way.  For steel fasteners against aluminum
castings (like the Stag water pump), they also help keep the bolt head from
tearing up the casting.

Fastener technology is one of those things that looks simple at first, but
the more you look into it, the more complicated it gets.

-- Randall