Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

The most likely possibilities that come to mind is that you have slack in your Ways & Gibs or backlash in your feedscrews that was not adequately locked down, showing up in your Y Axis. The other likely possibility is that the column for your spindle head is not quite fully cinched up where it mounts to your table base, or the machine is simply not ridged enough to handle the load that boring operation placed on the column/base joint, which then showed up as runout/movement in the Y Axis.

Pure speculation of course, but those would likely be the logical possibilities.