Used in exactly the same form on both the earlier South Bend 9-inch "Workshop" and later "Light Ten" -as well as Boxford and many other South Bend 9-inch copies and clones* -  the taper-turning unit remained virtually unchanged from the early 1930s until the 1990s.. However, setting up the unit to provide the required taper does require patience - and some manipulative practice - as it has to be set by hand, there being no screw adjustment. Further, locking the setting can upset it slightly, this often requiring a slightly false alignment before final tightening of the adjustment bolts.
When a taper-turning unit was fitted to a Boxford, instead of the usual single-screw, boss-held cross-slide screw nut, a special 2-bolt type with a flat top was fitted. Taking out both bolts allowed the nut to slide back and forth under the cross slide casting, so removing the need (as was required with the standard nut) of having to dismantle the assembly before the taper turning could begin. The first mention of a taper-turning unit for the 9-inch South Bend appeared in the dedicated sales catalog for that lathe in October 1935 - though this, and all subsequent versions right up to the 10-inch "Light Ten" lathes of the early 1950s , had just the ordinary nut and never a "quickly-detachable" type. However, a telescopic screw was always available on the company's larger lachines.
*Ace, Boffelli & Finazzi, Blomqvist, Hercus, Joinville, Parkanson, Purcell, Sanches Blanes, Sheraton, Smart & Brown, Storebro, Unitol, Select, NSTH and UFP..

Boxford cross-feed nuts: on the left the standard type, on the right the "quickly-detachable" version fitted to lathes with taper turning.
Both are available from lathes.co.uk