Secret to centering a lathe chuck ?

Mine is very slightly off centre and thus out of allignment

I have 3 bolts on the back plate that fix it to the lathe and when they are loose they allow some movement to centre it and adjust -

but I can't seem to get it right -

I've tried putting a straight pipe in the chuck and pushing the up to it with a centering chuck on the other end -

everything looks aligned but when i power it up it still gives me a tiny wobble ....

never did before until I took of the chuck so that I had more room for a milling project ... my mistake ...

just need to get it back to the way it was ... any advice would be appreciated -

Cheers

James