There is only one to get them 100% true this come from the experience of manufacturing part for old bugatti engines if you want the this way you need to gun drill the hole leaving a mirror finish the place the bushing on to a precision made mandrel and either grind or turn bettween centers you will end up with it been 100% true then the run out should be tested but that would be extreme way of doing it
With case hardning you really need to grind them after hardning to take in to account any Stress (can't think of the right word). I think it best to use 316 stainless steel and have them made in one operation rough the od then spot drill the hole then drill and ream then finish turn then do a part transfer to the sub spindle then finish turn the face and chamfer the hole once made they should be test for any run out if there is any the spindle are out of alignment
