I turned a piece of 5/16" diameter 12L14 steel down to 0.2755" in 0.005" increments using a carbide insert cutter, then down to .02750" using 400, 600, 1299 and 2500 grit oiled sandpaper. The material projection from the ER32 chuck was 0.6875", using the L/D rule of thumb I figured I'd be good for up to 0.825", 3 times the finish diameter.
From the chuck end of the cut, my DTI indicates a near-perfect axial zero reading up to about 0.4602", then it falls off rapidly, and linearly to the TS end of the piece. The taper at the end is radially 0.0015" less than the chuck end.
My first thought is this must be due to workpiece deflection but since my L/D ratio is "in-spec", I wonder if there's something else going on?
I've already corrected the lathe for bed twist and don't believe it would cause such a rapid taper at one end of the work while allowing roundness further back.
Also wonder if maybe this might be caused by a wear spot in the ways; either low or high?
I may try using a dead or live center on a piece to see if it's deflection-related, thought I'd ask here first.
Thank you.
From the chuck end of the cut, my DTI indicates a near-perfect axial zero reading up to about 0.4602", then it falls off rapidly, and linearly to the TS end of the piece. The taper at the end is radially 0.0015" less than the chuck end.
My first thought is this must be due to workpiece deflection but since my L/D ratio is "in-spec", I wonder if there's something else going on?
I've already corrected the lathe for bed twist and don't believe it would cause such a rapid taper at one end of the work while allowing roundness further back.
Also wonder if maybe this might be caused by a wear spot in the ways; either low or high?
I may try using a dead or live center on a piece to see if it's deflection-related, thought I'd ask here first.
Thank you.