Take the screw with you to an Ace Hardware store. Get not just one, but several that match the thread size. The cost should be about 60-90 cents as apposed to buying them from nova. Of course, the head size is going to be just a tad larger then the hole, but the easiest thing to do is remove all the jaws, mount the chuck back into place. With the chuck key in place, tighten the jaw mounts until they are tight on the screw. If you have carbide, use it to remove a little material off the OD of the screw head. The amount you remove is about 1/32". Loosen the jaw things , remove the screw and see if it fits in the screw sockets on the jaws. If not, remove some more. Since you got more than one screw, do them all as you will probably need some new ones later. ................. Nubs