I am trying to make an aluminum shaft out of 1.25 stock, shaft portion finishes at .860 and is about 10 inches long. When turning .01 finish pass, starts chattering about 1 inch from tailstock untill about 3 inches from end of shaft. Tried 3000 rpm, 1500, .005 feed and still chatters. not shure what im doing wrong. Tail stock pressure is about 90psi. Any Ideas??