Square block material hows that aligned on a lathe?

[BillTodd]

Square block material hows that aligned? same procedure for round bar?

Pretty much. You need to ensure the DTI is dead on centre then compare opposite faces by rocking the chuck for a minimum reading

The only way I can think of centralising a square block is drawing a diagonal lines across its corners and finding the center,then slip it in the chuck.Stick a center in an arbour on the tailstock,offer up the tailstock to the workpice and adjust the center mark on workpiece to align with center.?

It is easier and more accurate if you trap another lathe centre between the tail-stock centre and the centre-punch dot, then set the DTI on the trapped centre (alternatively make yourself a wiggle centre like this - http://www.frets.com/HomeShopTech/To...glycenter.html)

[edit] There are some real gems on Frank Ford's site, well worth reading.

Bill