Look in your manual to see if you have inverse time (G94?) feedrate.
Calculate the length of time needed to complete the cut.
Divide it into one. (1/t)
A feed of F.5 means it should take 2 seconds to complete (1/2)
A feed of F.02 means it should take 50 seconds to complete (1/50)
So let's see...
A cut at 3" from center, moving 360° all together, at 15 IPM....
6 X Pi = about 18.5" circumference
18.5 IN /15 IPM = 1.256 minutes, or 75.36 seconds
Invert that, 1/75.36 = .0651
So you'd program G94 F.0651
The feedrate you're currently using is in degrees per minute, and usually, there's a parameter that clamps cutting feedrate on the rotary axis. But your problem seems to be the command format of 3.4.I don't know how to overcome that. Someone more familiar with the Fanuc system might be able to help there.
Inverse time bypasses that clamped speed entirely, and hopefully doesn't exceed the rapid for the table ( never had an instance of that myself... )