Has anyone had any luck fitting non-original lenses to their 4x5 RB Series B? Are there any other lenses besides the Kodak 7.5 inch that screw into the original mounting flange?

Lots of other lenses work. I have a Zeiss Tessar 15cm lens on mine and it works great.

I suspect that the threads you are talking about is the flange that mounts your existing lens. It is unlikely that another lens will fit that flange, although it is possible. Each lens should come with its own mounting flange; if it is missing you should demand a very steep discount as they are hard to come by and the lens cannot be used without it.

Should you get another lens with its own flange, it may not fit the board you have now. Make your own, using the many comments on the subject found on this site.

When I mounted my Tessar, I had to space the lens flange away from the board by about a half inch to allow clearance between the mirror and the rear element. Be sure to check this before mounting a lens. There is a careful balance point between being able to get the lens to go to infinity and clearing the mirror, which is why short focal lengths cannot be used.

Thanks for the reply. I was wondering if anyone had actually found another lens besides the original 7.5 Kodak that would screw into the mounting flange, or could be adapted to fit. For instance, can the 190mm lens from a 4x5 Super D be screwed directly into the flange of a Series B?