Using spindle-synchronised offsets to the cross-slide position to bore a hexagonal hole. This uses EMC2 software (www.linuxcnc.org) with a custom HAL component that interpolates an offset from a table based on the spindle encoder position, then adds that to the X-axis motor position.
My lathe has an ungeared head and won't actually run slowly enough to allow the X-axis stepper to keep up, so I am hand-cranking the spindle from the back (which is why the spindle speed is not very constant)
