.... broach a hex hole in mild steel.

Anyone see a problem with this method?

I have two parts sent to me that already have a .250" hex
in them, and my friend wants them opened up to .375" hexes.
I tested one, and it drilled out very easily and nicely.

My plan right now is to make a shaping cutter to fit my
Bridgeport Shaper/Slotting Head that has the width of
one flat of the hex (.217"), place the piece in a 5C collet,
the collet in a hex shaped collet block for easy indexing
in the vise, and broach/slot the hole to a hex shape.

Warnings? Admonitions?
Vulgarities? Suggestions?
A better idea?

Thanks,

Weyland