Joe wrote: "From whence does the term originate to label a hypotenuse measurement as a "parallel" dimension, and how often and by whom is it used this way?"
Yeah, I know it's confusing. In drafting, a "parallel" dimension is defined as I described it - maybe because the dimension is taken parallel to the endpoints? Dunno. Maybe it's a singular example of a rhetorical figure in which an epigrammatic effect is created by the conjunction of incongruous or contradictory terms?
Anyway, it's always been that way as far as I know and it's how I was trained and never bothered to question it. It seems to have stuck because every modern CAD/CAM package I've used since calls it the same thing.
Cheers!
Don Ferris
Anvil Bikeworks, Inc.
Littleton, Colorado
Ph: 303.471.7533 / 303.919.9073
Fax: 413.556.6825
http://www.anvilbikes.com