Steve: Burnrider had it right, the 200 has two controls on the apron in addition to the handwheel: The push-pull knob for the power cross feed, which does use a gear arrangement in the apron to operate it; and the half nut lever, which is used for all longitudinal power feed, whether threading or just removing material. This system requires the availability of more change gear combinations
than does a machine that uses a quick change gear box.
The 815 had both power cross feed and power longitudinal feed through a set of gears in the apron, plus feed for thread cutting was handled using the half nut. On a lathe having a quick change gear box, such as the 815, there are actually two rates of longitudinal feed for each setting of the change gears. One is a feed rate in inches per revolution (expressed in thousandths) used for cutting using the longitudinal feed, and the other is a feed rate in threads per inch, which is the result when using the half nut.
Bellwether, my apologies for letting things get carried away. I would like to recommend that you look through a copy of "How to run a lathe" from South Bend Lathe. You can get to a PDF of the entire book from 1914 here:
http://books.google.com/books?id=sA...a=X&ei=0GJ7UbvvGcruqwGjrYDYDg&ved=0CDoQ6AEwAA The basics are still the same now as they were back then, but you can safely ignore the section on setting up lineshafts. Reprints are available of newer versions on eBay and from a few other places as well. It will teach you all of the basics of lathe operation and you will find it to be invaluable. If you are interested in more general machining knowledge including drilling, lathes, shapers, and mills, I would suggest getting a copy of Machine Shop Practice Vol 1, and Machine Shop Practice Vol 2, both by Karl Hans Moltrecht. Here is what is covered in each, the following is from Enco's website:
Covers everything the apprentice or on-the-job professional needs to know about the intelligent and efficientoperation of machine tools.
Vol I
496 pp. Contents: Basic Metalcutting; Basic Measuring; Layout Work; Drilling Machines, Twist Drills andTooling; Engine Lathe Construction; Single-Point Cutting Tools; Cylindrical Turning; Chucking Work; Taper andAngle Turning; Faceplate Work; Screw Threads and Measurements, Cutting Screws; Turret Lathes; ProductionLathes; Vertical Lathes; Precision Hole Location; The Jig Borer; and Metal Cutting Saws; Appendix; Index
Vol II
517 pp. Contents: Shaper Construction and Shaper Work. Planers and Planer Work; Milling Cutters; Milling-Machine Operations; Indexing; Dividing Head Work; Surface Grinding; Cutter and Tool Grinding; Numerical
Controlled Machine Tools; Surface Plate Work; Appendix
Each book can be had for under $25 new if you look around a bit, even cheaper if you buy used. They are excellent resources for anything relating to metal working machines. They will not cover every possible detail of every machine, but they cover more than enough to get you going safely and properly. Additionally, you can always ask questions here in the forum.
Let us know if you end up with the lathe that you are considering, and feel free to post some photos. There's nothing to make a guy feel good like a good tool-gloat. Well, except maybe a cold adult beverage. "Self medicating" is allowed in this hobby, but only AFTER all of the machines are shut off for the day.