For studing the grinding specificityof cubic boron nitride （CBN） wheel and aluminum oxide （GB） wheel

five types of casehandening gear material. including20CrMnMo

20Cr2Ni4

20CrNi2Mo

15CrNi3Mo and 17CrNiMo6 are tested.It is shownthat the grindinfi specificity of CBN wheelis quite superior to that of alllminum oxide wheel.Calculation and Design of Uneven Film Chuck forGrinding Gear Holes Chen Chuxuen

et al. （45）Abstract The construction and calculation of thechuck introduced in the paper has been improved basedon the thesis [1.j

the even plate of .the film chuck ischanged into uneven one. After improving

deformation and streess distribution of the film plate is morereasonable and the property is better

and the life islonger.