Interpolating bearings seats can be tricky in the mill unless the machine is in excellent shape and the servos tuned with equal excellency. The possibility exists that the hole may be irregular and difficult to measure accurately with a micrometer. Best to check the absolute roundness of the hole with a dial indicator mounted in the spindle, and sweeping the bore.
Once you have determined that the hole is round, then you can begin to believe your micrometer. If the hole is not round, then a boring operation may be the better option for finishing. Also, tool wear will have less effect if the boring tool is saved for only a final cut.
Beware of the effects of clamping pressure if holding a relatively flexible part in the vise when machining this hole. The shape could change when the part is removed.
BTW 30mm = 1.1811" , in case you're wondering what is the basis for the strange figure that you measured
First you get good, then you get fast. Then grouchiness sets in.
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)