Posted by Jim Pollock on September 14, 2009 at 22:35:31:
I bought an old Barber Colman #12 gear hobber a while back and I am just now getting around to running it. I cut an 8620 steel spur gear that is 7 dp and it has 30 teeth. I was running the hob as slow as I could with the speed change gears that I have which is about 120 rpm. My hob 3" in dia. This is the first I have run a hobber so I didn't really know what to expect as far as depth of cut is concerned so I took a few cuts of .100" and it seemed to be cutting pretty nice. For my finish cut, I only took about .050" and the finish on the teeth is much worse than when I was taking .100. I was running about .060" feed per revolution of the gear. How much should I take for each cut? The finish looks like I was not loading the hob enough and causing it to kind of get out of sink with the gear slightly. The machine does have a flywheel on the side of the hob slide and it does a little backlash in the gears under the hob slide. Is there a way to tighten these up?