As well as the linked thread, the nuts are a 'consumable' item. They were originally Mazac/Zamac/zinc alloy and wore in preference to the feed screws. They are an easy, cheap replacement and worth doing before you replace the screws themselves, but the cost of the complete screw+nut assembly is cheaper than the original Myford Beeston parts were.. The Myford/RDG web site has them listed.

Just had a look at the Myford/RDG prices and have to say the word "cheap" did not come to mind, but perhaps that says more about me than anything else. Over £400 for a topslide , good grief you could buy a whole Chinese lathe for that.

Doug

For power crossfeed on the S7 you need to purchase the nut/screw assembly, otherwise you can just purchase the nut, unless it has worked hard in an industrial environment. My S7 was 25 years in an industrial setting, I replaced the nuts when i acquired it.

Everything else can usually be fixed by adjustment

There is also the old dodge of cutting the threaded section off the screw, turning it round endwise and re-attaching it with a suitable spigot pin and silver solder. This moves the worn section to the least used end of the leadscrew. Works best with the main carriage leadscrew but not sure where the cross-slide nut rides on the S7. If its in the middle then obviously no advantage to be gained but if its at one end could be worth doing if the screw is badly worn.