Turn a blank between centers, turn one end down to 3/4", make this about 2" long. Then mount that in your collet chuck, and make the mandrel. It will always be on center and reusable until you lose it.
No collet chuck? Take a 3" lag bolt and screw it in one end, then cut the head off and chuck it into your drill chuck in the headstock. Turn he blank round between centers and make the mandrel on the end. The bad part about this one is you need a draw bar if you do not use your tailstock.