Trolling Tad asks:

>OK now - you can't just leave that hanging out there in the breeze...
>Care to enlighten me about what a sin bar is?

I'll take this one as a sine bar is the first "prject" after a square, that
the apprentice student makes in Trade School.

this could get interresting to describe w/out pictures though

simply put it is a rectalinear bar attached to two cylinders of equal diameter.

like this:

__________
0               0

if one were to set it down on a surface plate and zero a dial indicator on
one edge and then run the indicator along it's length.. it would remain
zero.....
IOW, the top plane of the sine bar is parallel to the plane created by the
"bottom" of the feet...
But it is really not it if for checking parallel, it is used for angles
.... Since by placing a "step" of a known thickness under one of the feet
the top surface becomes angular to the surface plate by a known degree.....
is this making any sense?

tomorrow lessons: Compound Sine Plates

Class dismissed.

Hey Ron, anything you wanna add?