in fact ,the lathe spindle will have a tapered bore that will hold a centre of some suitable size......might be big one ,like #5 Morse,so the lathe will also come with a spindle bush ,whic is #5 Morse on the outside ,but only #2 on the inside...to take a #2 centre.......notice that no chuck is involved so far.....Now normally ,you will also have a catch plate which will have one or more slots to drive a bent tail dog....a straight tail dog will need a stud out from the plate face............now a chuck can also be used as a catchplate ,if you dont have one.....with a bent tail dog,simply remove the jaws ,and use the slots.........a straight tail dog ,can use a chuck jaw to drive the dog......hoever you need to leave on opposite jaw in to balance the chuck,and be careful it doesnt catch anything as it rotates......this will incluse your knuckles.......All this is explained in the South Bend "How to use a lathe "book....which is available free online