[th3t1ck]

I have been getting familiar with 3 axis CNC work in metal and wood and would like to add a 4th axis. My controller will handle 5 axis. I see 4 axis stuff on ebay that look like lathes. Is that the only setup? Is the 4th axis A or B (as in XYZAB)? Anything I should look out for when purchasing a 4th axis setup?

[alearner]

Are you using a general purpose cnc lathe machine or other kind of CNC machine? for different kind of machine, the definition for 4th axis will be different, such as the CNC turn lathe and CNC machining center.

[th3t1ck]

I am using a home made CNC based on a 24"x36" frame from mekanikacnc.com/ so I think the right answer is i am not using a lathe type CNC.

[CaptainVee]

I use my 4th axis in a- and c-setup, both for indexing and lathe work.

I think that you need to get used to only seeing the profiles in xyz and nothing in a or c.
If you run more then one profile in one program things can get mixed up easily.