There are several problems encountered when fitting any sort of chuck to the spindle of a wood lathe:
1) the thread diameter and pitch might not be listed and is unknown
2) the spindle thread might be some odd-ball form
3) on a metal lathe, chucks can often be bought that just screw on, but are rare for wood lathes. On most metal-turning lathes to mount a chuck a suitably threaded cast-iron backplate is screwed on and then turned so that it a close fit into the back of the chuck to make sure it aligns with the spindle. The bolts that pass through the backplate and screw into the body of the chuck do not align the two, just clamp them together.
On a wood lathe this process usually cannot be used - unless the lathe is one of the few fitted with a metal-turning slide rest - and the job has to be done on another lathe.