See: Types of Machines Overview 

(a Presto 6N picture from the 6N manual)

Presto 6N - A very common and popular semi-pro lathe.  A very good choice for a beginning or intermediate cutter who wants a relatively inexpensive, yet solid, machine with easy to find parts and accessories. Built from the late 30's to the mid 50's during which time it remained relatively unchanged. Used extensively in radio stations and small recording studios.  Uses exchangable feedscrews to determine length of music per side/width between grooves. Commonly used with Presto 1c or 1d cutter heads, but also fit Grampian Type C and some other heads webmail.

(a Rek-O-Kut Challenger, picture from www.minniepaulmusic.com)

Rek-O-Kut Lathes - Similar to Presto 6Ns, though typically a little less beefy.  Many models came with built in amplifiers.  These used proprietary feedscrews which had an accompanying half-nut that was installed inside the head carriage. Feedscrews for these models are much rarer, and even harder to find with the required matching half-nut.