Fred Holder wrote:
Jean-Fancois Escoulen considers the work done by his ball and socket chuck to be
eccentric. Robert Sorby considers the work done by their eccentric chuck to be
eccentric although it basically performs the actions described in 1 above. It is
all multi-center turning.

I think they are both right.

My dictionary defines eccentric (in the context we are looking at)
simply as 'not having the same centre as another'.

According to wikipedia eccentric is the opposite of concentric
http://en.wikipedia.org/wiki/Eccentric
http://en.wikipedia.org/wiki/Concentric

"In mechanical engineering, an eccentric is a wheel that rotates on an
axle that is displaced from the focus of the circle described by the
wheel..."

I suspect that in most mechanical applications the axes are parallel to
one another.

Therefore I suggest that the case where the axes are not parallel is
just a special case of eccentric. If there is not already a word or
phrase that describes this special case, maybe there should be.

Other variations to consider are the possibilities that the axes are
either convergent or non-convergent. (they either intersect at some
point, or never meet)

--
Derek Andrews, woodturner

http://www.seafoamwoodturning.com
http://chipshop.blogspot.com - a blog for my customers
http://www.seafoamwoodturning.com/TheToolrest/ - a blog for woodturners