A rod in a chuck that runs out will describe a cylindrical path when turned, that is, the rod's center axis will be parallel to the spindle axis and "orbit" around it. Swash will yield a conical path in which the rod's center axis is NEVER parallel to the spindle axis.
So if the runout increases with distance from the chuck, this suggests swash.
Robin Snyder
This is correct.
It is like a wobble or the faceplate not true to the run of the spindle. Turbine compressors suffer from swash problems as well. So it is balanced but the front or back face does not run true or zero. In a turbine situation the faster it spins more out of true it will run and eventually cause a strike with the housing which becomes a disaster.
lathes just run further out from the chuck, but hold the workpiece not true.
Even though you bore the chuck jaws, when swash is present,the jaws will only be correct at that exact size. As the jaws open up, the position changes and so a test bar of a different diameter will be different and not run true.
On my lathes I face the chuck mount true,then I set up the 4 jaw chuck.
Turn a piece of steel and close the chuckjaws onto that.I put a DTI (dial test indicator) on the now backface that is facing the tailstock.I give it a light skim cut to make it true.I also check the front face to see how that is. After getting it correct, I usually face the front face with a skim cut after it is assembled back on the lathe. I also check the back face to ensure it is running zero when it is placed onto the spindle.
