The teeth and cogging of bevel gears are all contracted, that is, the big end is wide and the small end is narrow. Although the indexing head has been raised by a root cone angle during machining, so that the big end of the outer conical surface of the bevel gear is slightly higher than the small end, the big end is deeper than the small end during milling, and the width of the tooth slot is slightly wider than the small end, but this difference can not meet the requirements, and more tooth slots need to be milled at the big end.