[chrisbec]

I ground the chamfer in the bottom of the outer BJ hole with my die grinder and a well dressed stone. Then I went over it with a flap disk to remove any burrs left over from grinding. To chamfer the sharp 90 degree edge that was left after boring is important so that the knurls on the ball joints don't get sheared off when the parts are pressed together. The chamfer will allow the knurls to dig into the inner bore of the arm so they remain effective in retaining the ball joint in the arm.