I tried using a piece of round stock and was having no luck. I changed to a piece of copper wire and got slightly better. In both cases they were about the width of the chuck. I don't know if a shorter piece would make any difference. I checked the vise ways and they are level within .0002 over their exposed length. The vise fixed jaw is square within .0001 over its height. The fixed jaw flexes .0003 when tightening stock. Mill is trammed well within a half thou over about 6 inches. The only thing I have found that helps is a piece of paper extending about .25 from the top of the fixed jaw. It overcorrects by between 1 to 1.5 thou but I don't have anything thinner at the moment. I think I'll pick up some cigarette paper and try that since it is thinner. I'm probably chasing my tail but I would like things square a parallel within a thou for the start of the block.