Sirs:
Yes, a good screwdriver - yes they still bugger!
I try to put the metal back both on the sides and top of the screw and as Jim says, use your hacksaw blades (I've got ten hacksaws - I've got a "thing" about hacksaws and hammers
).
I peen down the screw head and then put it in the drill press and with a fine file and contour the head, not forgetting the sides. It should be bright.
Then, with it held solidly in the vise I do Jims' hacksaw trick - always using a backstroke to take teeth marks out, and polish again in the press. The final polish takes some good 240 and a stiff finger to make.
I've got a can of wretched used engine oil and heat the screw and head to a good blue color (about 700 degrees F. and plunge it in the oil and then withdraw it quick enough so it smokes and touch flame again and again dipping and burning oil off each tome - it works! Work fast or your color will go to grey then you'll need to start over again - this is a chemical change in the steel.
Then sit back on that ego trip like some do and never tell a young smith any of your secrets. Old Harry Pope, crichity, mean old smith he was - when he was old he so, so wanted some young man to tell his secrets to.
So many smiths, when old and knowledgeable, like to act like Gods;' elder brother - what a shame -- here on the Forum we welcome young smiths and inquiring minds and we'll all help.
Harry B.