| 摘要 |
PURPOSE: To minimize edge contact and/or interference causing noises by plunge- cutting a rotating hob to the longitudinal axis of a blank in a point a little biased from the longitudinal middle point thereof from one side of a rotating worm wheel blank. CONSTITUTION: Raw material 50 of a combination gear having a double enveloping wormwheel portion 52 and a spur gear portion 54 is rotatably installed round a vertical axis 56, and a hobbing tool 58 having the substantially same tooth form as a skew gear is supported rotatably around the horizontal axis 60 to cut in the radial direction along a path 62. The hob 58 is smaller than a usually used hob to obtain a desired mismatch amount. The path 62 is biased from the middle point C by the amount 'A', and on reaching a predetermined cut position subsequently it passes an axial cut area indicated by 'B' striding over the axial center C along a path 64. Then, additional relative rotation is applied to the wormwheel to follow a desired twist angle, thereby creating curved portions regulated by radii R and R on both sides.
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