Fenchel cutting planes are based on the dual relationship between sepa
ration and optimization and can be applied in many instances where alt
ernative cutting planes cannot. They are deep in the sense of providin
g the maximum separation between a point ($) over cap x and a polyhedr
on P as measured by an arbitrary norm which is specified in the proces
s of generating a Fenchel cut. This paper demonstrates a number of fun
damental convergence properties of Fenchel cuts and addresses the ques
tion of which norms lead to the most desirable Fenchel cuts. The stren
gths and weaknesses of the related class of 1-polar cuts are also exam
ined.