I recently purchased a G4003G. I had originally wanted the G0750G but due to delivery date of Nov/Dec. 2013 I went with the G4003G. This is a very good lathe and is extremely stable and smooth. I did not find the differences in the gearboxes to be a game changer. I am more than satisfied with the purchase and have found Grizzly CS very easy to deal with. Although I have not had any problems of significance, they did respond quite quickly to the questions I did submit. Having a store front reasonably close is also nice. Bellingham is about 2-1/2 hours from Gig Harbor in Wash. Delivery was extremely fast. I do gunsmithing and none of the threading features have been a detriment. It does everything I have ask of it and does it well. I concur that threading more than 48tpi would be extreme and difficult. Unless you are contracting to NASA you should be capable of doing very good work on this lathe.
Hope this helps. I read everything in print before making my purchase. Since then I have relied on opinions on this site for other projects. Good information is available.
Hope this helps. I read everything in print before making my purchase. Since then I have relied on opinions on this site for other projects. Good information is available.