A few additional thoughts: If I understand this correctly, the spiral advances towards the headstock with every pass; total accumulation being approximately 1/8" in 8 passes? Are these screwcutting passes being taken with the back gear engaged? If so, have a look at the back gear assembly. Although you can't see it, this gear is supposed to be secured to the spindle with a shallow woodruff key (re: Section H, Headstock Assembly, Super 7 manual). It should be impossible to turn the gear while holding the spindle. If it does move, it may indicate a sheared key, or no key at all. There should also be a socket set screw securing the gear laterally to the spindle, located in the shoulder of the 60 tooth gear, on the righthand side. If it's not tight, suspect a problem with the key. And for a wild card, is the problem occuring with the standard topslide installed on the lathe or an accessory, such as a retracting topslide? Pat Dworzan