Why can't the shoulder root radius too big nor too small, how to value

Shoulder fillet is too big or too small can cause what problem actually, speak in the mechanical design teaching material very clear: radius is too big, round hole part of the bearing chamfer may compare is small, so the rounded and chamfering is intervention, the bearing and the shaft shoulder depend on not tight, using easily provoked vibration; Radius is too small, easy to produce stress concentration, shaft shoulder will affect the strength of the shaft. Shoulder fillet size values match well, therefore, the shoulder root fillet radius must be less than the radius of bearing inner ring, ordinary should be half of the bearing inner ring radius, talent guarantee bearing close to shoulder; Consumption verticality and fillet size shoulder when how to test the shaft shoulder of vertical degree with right Angle size mandrel shoulders, make its closed, then borrow the light or sunlight, such as average or not light-leaking light-leaking, vertical shaft shoulder. The shoulder root fillet radius available model test. Bearing and shaft device, it is necessary to check the shaft neck shoulder verticality and shoulder root radius fit request can use;