All pieces are machined with .0001 precision. The front & back bearing mounts are concentric within .0001 also. The ball of the universal (.3125 dia) & the center shaft (O-1 tool steel) are machined as one piece to ensure concentricity. Notice the blue colored ball end (spring temper) which allows a .001 interference fit of the 4mm (.1575 dowel pin), without splitting the ball. This pin NEVER comes out & can be replaced when worn. This procedure is done in a fixture.
