Posted by Ron on December 13, 2005 at 22:49:08:
In Reply to: Gear Hobbing on a lathe posted by John Burridge on December 10, 2005 at 22:18:54:
You can only hob a worm wheel on a lathe. Because the job is "free wheeling" it can only be plunged into the hob. The wheel is usually gashed in a milling machine first to provide points where the helix of the hob can pick on to provide the drive to rotate the wheel. In answer to your question: No you can't use power feed because of the configuration.
Bill, the hob is mounted and driven between centers. The job is mounted to a fixture and then held horizontaly in the tool post and allowed to rotate freely. It is then plunged radially into the hob. As mentioned this only works on worm wheels. It can also be done in a milling machine. Usually it's only the fine pitches and usually a tap such as an acme thread is used in place of the hob.
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