The steering knuckle bushing is interference fit in its seat hole, and the axis of the upper and lower holes is the same straight line. Because of the deformation of steering knuckle, conical and circular bearing holes, deviation of axes of two bearing holes and interference shrinkage of bushing pressed into seat holes, standard bushing and main pin fit are used, and there is no suitable clearance. Reamer reaming is needed to fit the main pin journal. However, because the upper and lower holes of steering knuckle have a certain distance, and the reamer length of reaming bushing is insufficient, two holes can not be reamed at a time, only the upper holes are reamed first, and then the lower holes are reamed. This will inevitably result in two different holes, the main pin can not pass through the lower hole after it is put into the upper hole, and finally only one hole is reamed and enlarged to make the main pin in place in the two holes. Result There are only four contact surfaces between the main pin journal and the inner hole of the bushing. When the car is running for a period of time, the four contact surfaces in the two bushings are quickly abraded by the main pin journal, resulting in large clearance, which forms the main pin and bushing of steering knuckle loose.

To ream the bearing hole of the main pin bushing of steering knuckle with adjustable reamer can ensure its concentricity. The method is to add a cylindrical guide rod longer than the main pin to the end of the reamer before reaming the bushing. The guide rod is tightened at the end of the reamer, and then a 60 degree taper sleeve is made. Its inner hole slides with the cylindrical guide rod. When reaming the first hole of the bearing hole of the main pin bushing of steering knuckle, the cone sleeve is used to locate the second hole, and when turning the head to ream the second hole, the cone sleeve is used to locate the first hole. The two holes can not be reamed in the same direction at once. The above steps must be followed, otherwise the concentricity of the two bearing holes can not be guaranteed. The joint of the main pin and bushing should be more than 70% so that the main pin bushing can be used durably.