This article is from the Fencing FAQ, by Morgan Burke with numerous contributions by others.
The length and thread of the tang may be an issue; some blades
are threaded for French or pistol grips only, and some blades
with French grip tangs require an extra fitting for the thread.
Italian grips may require a special tang, since part of it is
exposed in the hilt. Metric 6x1 threading is standard, but not
universal (esp. in the USA, where a 12x24 thread may be
encountered); dies to re-thread the tang can be found at most
hardware stores. If the tang must be cut to fit the grip, be
very careful to leave enough thread to screw on the pommel nut.
Tangs often have to be filed down to fit in tight grips.
Tangs are attached by an exterior pommel on traditional grips, or
by a pommel nut in pistol grips. Pommel nuts are typically
fitted for a 6mm Allen wrench or hex key, 8mm socket wrench, or a