email@example.com wrote: IIRC, the 6"
That would be the AA "toy"lathes - 1/2" Mt-0 spindle on bronze sleeve bearings. These are about the size of the 7x10 minilathe but much lighter. Vee ways.
The 618 has a quite robust spindle approx 1" OD, Timken tapered roller bearings, and a MT-3 spindle taper. These are about 3-ft long and weight 70-lbs or more, flat ways. They are nice lathes. I've had several, and I'll buy another if the right deal happens my way.
Zinc (Zamac) gears came with the AA and any other Sears-branded metal lathe, of any size or vintage. Most of those Zamac gears are still serviceable after 50 years or so, but there are also steel replacements on ebay. I haven't seen but a few that looked crumbly, and those had been poorly stored. FWIW - All the minilathes use plastic gears