Dimple-forming burnishing tool and dimple-forming burnishing method

Abstract

A burnishing tool includes a mandrel; and a frame fitted to the mandrel and holding balls contacting an outer peripheral surface on the mandrel. The outer peripheral surface has a contact surface with the balls. The contact surface is at a side of the outer peripheral surface which is closer to the work surface. The contact surface and the work surface have a distance therebetween in a direction normal to the work surface. A distance at a side of the mandrel closer to the processing machine and a distance at the opposite side of the mandrel have a distance difference therebetween. A diameter of the outer peripheral surface on the mandrel is set in such a way that the distance difference with the mandrel flexed during formation of the dimples becomes smaller than that before flexing of the mandrel.

What is claimed is: 
     
         1 . A dimple-forming burnishing tool comprising:
 a mandrel having an end side fitted to a processing machine for rotating; and   a frame fitted and fixed to another side of the mandrel from the outside, and holding balls contacting an outer peripheral surface of the mandrel,   wherein the balls on the outer peripheral surface contact a work surface for forming dimples on the work surface with the mandrel and the frame rotated,   wherein the outer peripheral surface has a contact surface with the balls and,   wherein the contact surface is at a side of the outer peripheral surface which is closer to the work surface,   wherein the contact surface and the work surface have a distance therebetween in a direction normal to the work surface,   wherein a distance at a side of the mandrel closer to the processing machine and a distance at the opposite side of the mandrel have a distance difference therebetween,   wherein a diameter of the outer peripheral surface on the mandrel is set in such a way that the distance difference with the mandrel flexed during formation of the dimples becomes smaller than that before flexing of the mandrel.   
     
     
         2 . The dimple-forming burnishing tool according to  claim 1 ,
 wherein the mandrel has a first sectional line which is positioned on the outer peripheral surface and at said side closer to the work surface,   wherein the first sectional line is defined by sectioning the mandrel by a plane which is normal to the work surface and includes an axis of the mandrel,   wherein the work surface has a second sectional line on the work surface,   wherein the second sectional line is defined by sectioning the work surface by the plane,   wherein the first sectional line and the second sectional line have a parallel degree therebetween,   wherein a diameter of the outer peripheral surface on the mandrel at the opposite side to said side closer to the processing machine is set to be larger than that at the side closer to the processing machine, so that the parallel degree with the mandrel flexed during formation of the dimples becomes smaller than that before flexing of the mandrel.   
     
     
         3 . The dimple-forming burnishing tool according to  claim 2 ,
 wherein the outer peripheral surface of the mandrel has a side shape in a frustum of a circular cone which diverges toward the opposite side to said side closer to the processing machine.   
     
     
         4 . The dimple-forming burnishing tool according to  claim 1 , wherein the balls are spaced apart from each other in a peripheral direction of the frame and in a direction parallel with the axis of the frame. 
     
     
         5 . The dimple-forming burnishing tool according to  claim 1 ,
 wherein the frame comprising:   a frame body fitted to the mandrel from the outside and defining first through-holes for the balls to be fitted thereto, respectively; and   a frame cover fitted to the frame body from the outside, having the balls projecting radially outward from the outer peripheral surface of the frame, and defining second through-holes which coincide in position with the first through-holes for preventing the balls from dropping out of the first through-holes, respectively.   
     
     
         6 . A dimple-forming burnishing method comprising: contacting the balls on the work surface to form dimples on the work surface using the dimple-forming burnishing tool according to  claim 1 .