Runout with closed end mandrel in Jacobs chuck

[mrmartyking]

I am making closed end pens and I bought a Jacobs chuck along with the closed end mandrels that Ariz. Sill. sells. Sometimes when I chuck up the mandrel, I have a lot of runout. Sometimes not. Am I putting it in the chuck incorrectly or do I need a more precision Jacobs chuck? It is a chuck with a #2 MT on one end and another taper that goes into the chuck head.
Thanks

 

[Whaler]

When I first started making closed end pens I used a Jacobs chuck to hold those mandrels as you are doing. I finally got smart and used my 4 jaw chuck, much better. Now that I have a collet chuck that is what I use.

 

[pensbydesign]

probably not inserted far enough in chuck and your catching the nut on the back of mandrel been there done that