Tom has it right, though I just noticed that the data sheet if for negative rake inserts and those I sent you are positive. Here's a photo of the correct page from the catalog. If you can't read it (I wouldn't be surprised), I can e-mail you a PDF.
The annealed 4140 would be the third group down from the top, the "high alloyed steels" and those shown as "annealed" in the first row. Follow that over to the grade you're using to get the cutting speed recommendation. Now discard that information because your lathe can't go that fast and you'd be afraid to stand in front of it if it could. ;)
Run the materials as fast as YOU feel comfortable, but do use the other pages I sent showing the various chipbreakers to pick the best one. Once you've selected a good chipbreaker with the feed range you need to run for the finish you want to get, then set your quick change gear box for that feed per rev. Now set a depth of cut that's also right for the chosen chipbreaker and have at it, with a VIDEO CAMERA in hand. :) I want to see this!
![[Image: positive_inserts_zps06a659fd.jpg]](http://img.photobucket.com/albums/v466/kenm10759/Misc/positive_inserts_zps06a659fd.jpg)
The annealed 4140 would be the third group down from the top, the "high alloyed steels" and those shown as "annealed" in the first row. Follow that over to the grade you're using to get the cutting speed recommendation. Now discard that information because your lathe can't go that fast and you'd be afraid to stand in front of it if it could. ;)
Run the materials as fast as YOU feel comfortable, but do use the other pages I sent showing the various chipbreakers to pick the best one. Once you've selected a good chipbreaker with the feed range you need to run for the finish you want to get, then set your quick change gear box for that feed per rev. Now set a depth of cut that's also right for the chosen chipbreaker and have at it, with a VIDEO CAMERA in hand. :) I want to see this!