Posted by BillS on April 20, 2006 at 13:18:51:
In Reply to: Problem with Fellows 36-6 posted by Ron V on April 18, 2006 at 20:39:49:
I wonder if the retreating cutter tip is damaging the newly formed tooth surface? It seems to me that any backlash in the cutter axis (or in the work axis) of rotation could allow the cutter forces to push one flank and then the other.
The way you describe the marks seems to say they aren't caused by the smooth involute flank of the cutter tooth, but by the cutter tip. This is the same action that results in undercut i.e. the retreating tooth tip interferes with the tooth flank opposite the newly formed involute.
Another thought: Maybe its not due to any looseness but maybe due to the cutter form. Aren't shaper cutters ground for tooth ranges? Unlike a rack form hob cutter, the involute form of a shaper cutter is surely influenced by the number of teeth it's designed to cut. I think that a pinion cutter is ground differently from a general purpose cutter.
Maybe someone can shed some light on shaper cutter differences and tip interference that could explain what you are seeing.