FILENAMES: offcenters1.jpg offcenters2.jpg offcenters3.jpg offcenters4.jpg DESCRIPTION: These are photos showing the effects of center drilling techniques on turning between centers on a lathe. Posted by Jim Rozen . Jim provided the following description: ================================================================= Here are a few pictures of an aluminum shaft that was turned between centers. One end of the shaft was faced and center-drilled on center, in a collet. The other end was faced off in the collet, but the center was drilled in 0.150 off center using a drill press. The shaft started out one inch in diameter, and about ten inches long. The final turned end on the offset center side is slightly tapered (about 0.0005 in a distance of slightly over an inch long) because of the bed on this machine being slightly worn and the tailstock setover being not quite right. Offcenters1.jpg shows the entire end of the shaft. Quarter is for scale. Offcenters2.jpg shows the offset center hole that was drilled. The line is the axis along which the center was offset. The scuff spots where the center actually contacted the inside of the hole are visible, on the right side the spot is down near the bottom of the hole, and on the left there is a ring of scuff approximately half way around the outer perimeter of the hole. Offcenters3.jpg is a similar view of the headstock end of the shaft, and similar scuff marks are visible. In this case the scuff at the bottom of the hole is oriented at the 6 o'clock postion, and the outer perimeter is marked between 10 and 2 or so. Unfortunately the lighting makes the entire perimeter seem a bit shadowed, but this is actually not so. Offcenters4.jpg is an attempt to show the surface finish which seems pretty good to me. No apparent waviness or ovality of cross-section apparent, better than 0.0001 inch TIR.