OK. (For future reference: Please take notes and mention exactly
how you measured 'roughly .0015 out near the chuck') Please define what you mean by 'acceptable cuts'. Again... from what you describe it is likely you have a 'slight dip' but it does not tell us how much and, most importantly, why. From what you are saying you were using the tailstock to make this test, in which case your '.0015 out' may be due to tail stock alignment, headstock alignment, bed twist, or bed wear. It may also be a combination of all four. The trick is to try and separate them in order to isolate and quantify the problem.
Yes... but checking just the bed, independent of everything else, requires some specialized equipment and procedures that you are unlikely to have access to. You can see and read up on one of way measuring by googling for 'king way alignment tool'. You will find most images and discussions point back to practicalmachinist.com. The son of the inventor of that tool is a member here (Richard King.) Finding a King Way Alignment tool is difficult and probably very costly. There are a number of people who have made their own copies. There are also a number of ways to cobble one together with a lot of rods and clamps.
That said... The simplest method to try and isolate and correct your problem is perform the 'test-bar' test. One way to do the test bar test is described in the Rockwell manual for the 11" lathe. You can download the manual from the 'RockwellLathe' yahoo group. I think you need to be a member... but a good idea to join anyhow.
Yahoo Groups The manual is in the 'Files' section of the group. But the method described in the Rockwell manual requires a pre-made precision test bar. You can find them but they are usually pretty expensive.
Another method is to use the test bar you already have but this time do not use the tailstock at all. This is often called the 'Turning Test Method'. For a reasonably good description see this:
http://neme-s.org/Model_Engineer_Files/Align1.pdf (page 915 lower left) When using this method it is important to use a free cutting test bar and a sharp HSS tool to minimize cutting forces and deflection of the test bar. I would actually make three 'bobbins' on the bar; one at each end and one in the middle. You will need the test bar you already have, a 1-2" micrometer that can read to tenths, and a sharp HSS cutting tool ground for finish cutting the material of your test bar.
Even if there is some wear to the bed ways as you suspect... you may be able to 'twist' some or all of it out using the test bar method.
You mentioned that you have already leveled the lathe but you did not mention how you leveled it (the above mentioned manual has specific instructions on doing this) nor what type and precision of level you were using. Leveling a lathe is fine and dandy. When a lathe is setup at the factory it is done with leveled. But it is not the final adjustment. As is often said here and elsewhere, there are lathes on ships that cut straight and true that may never be 'level'.
You may find that after gathering all the right tools and time spent learning how to scrape that $1000+ is a relative bargain.
Keep in mind... if the lathe is worn about 0.0015" for 8" of the bed length ten you will have to scrape approximately 60" (this includes the section under the head stock) of six surfaces
down to the level of the worn areas.
So, do the 'Turning Test Method' and tell us what you find.
-DU-
.
