During the process of overhauling and using of automobile engine, it requires the fit clearance between camshaft’s journal and plain bearing must be less than 0.15mm. When the clearance is greater than 0.15mm, the plain bearing should be re-repaired to restore to the normal fit clearance, thus to ensure the performance of car engine. In the actual repair process, it often use boring, reaming, or hand-scraping and other methods, but the above methods have a certain degree of difficulty to ensure the fit clearance’s size accuracy between the journal and plain bearing. To further enhance the size accuracy and also guarantee the repair quality of engine, it can use turning method to repair plain bearing.
　　In the turning process, the first step should to reasonably design & produce a wood mould supplying for the lathe, plain bearing which will be processed should place in the wood mould, and the fit between bearing outer circle & mould bore should be made under the cirumstance of the normal roundness error for bearing outer surface, then slightly push the bearing into the mould bore with hands. Secondly, adjust cutting tools for normal turning according to the required size accuracy for bearing inner bore, which is: "journal size + fit clearance + interference of bearing & cylinder bore."
　　1.Fit clearance
　　Generally 0.03-0.07 mm.
　　2.Interference
　　① Interference for slotted bearing generally is 0.07-0.19 mm.
　　② Interference for the overall bearing to load into aluminum alloy cylinder bore generally is 0.03-0.07 mm.
　　③ Interference for the overall bearing to load into cast iron cylinder bore generally is 0.05-0.13 mm.
　　3.Surface roughness
　　Ra for the surface roughness of turning bearing inner bore is 0.5-1.6 mm.
　　Based on the above technical requirements, one should make careful check and measurement to see whether it meets the technical requirements after bearing bores have been completely processed. If it is correct, please loading into the cylinder bore and inserting the camshaft for grinding experiments. If the fit is too tight, it can slightly scratch the bearing bore. When coating oil in the bearing bore and rotate the camshaft for a few laps, struck timing gear with fingers, it can flexibly rotate without freezing phenomenon; when toggling timing gear up & down, it should be no obvious sense of radial clearance. In this way, the quality assurance is superior to other processing methods.
　　Turning is much easier than hand scraping and other methods, which can both to ensure the concentricity of plain bearing, and to ensure the dimensional accuracy of the inner bore. In general, units with lathes can make processings, not only to improve economic efficiency, but also to ensure the repair quality for engine.