Picked up an overstock Alien X, label says built in Aug. of '09. Shooting in the string before sight and peep, about 100 shots, decided to finish it up. Sight screw would not start, a little dark in the shop so grabbed a light to see if there was dip, etc. Light on the subject - no threads cut in either hole. Smooth as a baby's ...

What is the proper size tap for those? Thanks