[john walker's workshop]

drilling without a drill guide is hit and miss. very easy to get off-center and leave a portion of the stud on one side of the hole. if you drill by eyeball, just be careful. it can be done, i've done lots of them that way, and you still screw up occasionally, no matter how good you are. centerpunch, look at the punch mark for a while and decide if it really is centered, move the punch mark if necessary by punching again at an angle, drill a small pilot hole, and finish with a fresh 17/64 bit. that will leave just the threads if you got lucky. then use a small pointed punch to work the leading thread out enough to grab it with needlenose pliers and twist CC-wise and pull lightly at the same time. if it's off-center, you have to dislodge the remains with the pointed punch, then drill for an insert. or you could totally drill out the stud after the pilot drilling, and tap for an insert. use the drill size recommended for whatever insert you use.