Hi Claude,
The best method found most accurate so far is by using the iterative alignment. Providing you have a CNC (DCC) machine, I suggest you measure two ellipses near each ends, construct a line from them, and use that line to align in plane, say for example, in XY plane. This line obviously end-up being your "Z" vector. Make that line your XY origin. Measure a point at one end to construct "Z" origin. If there is a keyway or like features on the shaft, I suggest you measure 2 points in that groove, at 180 deg. apart, construct a symmetric point from them, and use it with one ellipses to connect a line, and finally align to "X". Then save this alignment. If you have some knowledge about looping, you can iterate to redo this cycle for two more sequences, re-saving your alignment over the previous one, each time. If your probes are qualified at the same speed you are measuring your features, say about 3mm/sec. you should get very accurate measurements. To measure the rest of the part diameters, you may then use the circle function, taking about 8 points around to achieve good accuracy, however, the method will vary depending the software used. Hoping this will help...
Richard,
Bell Helicopter, Metrology Lab.