Measuring of the Minimum Value of Tension Preload in a Bearing to Ensure the Rigidity of a Spindle Unit During Repair of the “Bearing Outer Ring–case” Joint

Abstract

The article proposes a method for determining minimum tension preload when restoring stiffness of a joint between a case and an outer ring of a bearing. Stiffness is essential prerequisite for functioning of a spindle assembly in a metal-cutting machine. To large extent, stiffness of an assembly is affected by deformation of its supports, mainly the frontal one. During work, this influence increases due to weakening and displacement of “outer ring of a bearing–case” fit. Fretting corrosion wear is believed to be the main cause of this phenomenon. Usage of polymer compositions in restoration of joints increases stiffness due to contact area enlargement. Main task is to determine required minimum value of tension preload to fully restore stiffness of a fit. This experimental study includes finding stiffness of “outer ring of a bearing–case” joint directly and finding stiffness of a spindle assembly as a whole. Method proposed helps to define minimum tension preload in an adjustable front bearing with different values of hole wear in a case which have been restored with polymer composition. Minimum tension preload is defined at the intersection point of a bearingʼs stiffness-tensile curve with the lower boundary of the stiffness parameter range. This method can be used for fit and for a spindle assembly as a whole.