Where can I get a manual for the Ohio Forge Model 510-459 drill press

SOURCE: The chuck slides off the

You can increase your knowledge of Morse Taper by taking a look at the link below:

http://www.beautifuliron.com/mttaper.htm

The mating surfaces must be clean and mate perfectly for a good hold. If your chuck has been slipping for some time, metal may have worn away from the sides allowing for loose fit. Look into the chuck and see if the spindle has been hitting the bottom of the chuck. If the spindle is hitting bottom, the inside of the chuck must have worn allowing the spindle to hit bottom before the side. You could buy a new chuck or try fileing /grinding the bottom of the spindle so that it does not reach bottom before the sides can set. If the spindle is not hitting bottom, try cleaning the spindle and chuck with lapping /valve grinding compound to smooth all surfaces(apply compound and insert chuck onto spindle and turn by hand). Try just a few turns with compound to reveal high spots, or if you get an even grind, continue with fine compoind to make perfect mating contact. Test often so as not to grind away too much metal. Clean both surfaces and start drilling!