This article is from the Fencing FAQ, by Morgan Burke with numerous contributions by others.
Many foil and epee fencers prefer a bend at the join of the tang
and blade, so that the blade points slightly inside when held in
sixte. Such a bend is best applied with a strong vise to avoid
bowing the tang. A few fencers prefer to put this bend into the
forte of the blade instead. Be gentle; blades will snap if
handled with too much force.
A gentle curve in the middle and foible of the blade is also common,
and helps to square the point against oblique surfaces. Such a bend
must be smooth and gradual. Sharp kinks are prohibited. Foible
bends are best worked into the blade using the sole of one's shoe
and the floor.
For foil and epee, the total curvature of the blade is measured
at the widest separation between the blade and an imaginary line
drawn between the the join of the forte and tang and the point.
The blade can be laid across a flat surface such as a table top
to measure the arch. Epees must not rise more than 1 cm above
the surface, while foils are allowed 2 cm. If the objective is
to angle the point to hit oblique surfaces better, this is a
significant amount of curvature. If the objective is to "hook"
the blade around blocking parries or body parts, however, these
limits are fairly restrictive.
Remember that the wire groove on epee and foil blades goes on the
top (thumb side) of the blade, and the outside of the blade
Sabre curvature is handled differently, it being the deflection
of the point from the line of the forte. 4 cm is all that is