Re: barber colman #12 gear hobber questions

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Posted by BillS on September 15, 2009 at 00:03:46:

In Reply to: barber colman #12 gear hobber questions posted by Jim Pollock on September 14, 2009 at 22:35:31:

I would look for play in the following areas:

Your index worm/worm gear may have slack motion. Put an arbor and gear in place. Put a dial indicator on a tooth, then torque the arbor back and forth. You should not see any appreciable motion. There are two adjustments - one for worm end play, and one for worm mesh. Don't try to take it all out, otherwise heat will cause it to seize up. Be sure there is a good bath of gear oil in the worm gear housing, up close to the inspection port.

Next put the dial on the end of the hob cutter shaft. Using a pry bar, try to move the cutter back and forth in the direction of its shaft. Again, there should be no motion.

The no. 12 as I recall, has a taper bronze bearing and cutter shaft.

Wear in the taper bearing will allow the shaft flange to ride on the bearing thrust surface, and the taper will not keep the shaft supported. You can see this play as axial motion of the cutter shaft, i.e. up and down. There is no variable adjustment here. You will need to decrease thrust washer thickness, or turn off a small amount of the shaft flange to get a good bearing fit.

That's about it. Usually slack in index and hob cutter show up when the machine is lightly loaded, i.e. finish cut. Also make sure the flywheel is a tight fit on the cutter shaft.

Other Wear Areas:
The feed screw has an adjusting nut, but when the feed screw has worn in a small range, adjusting the nut will only cause it to bind when drawn over the unworn part of the screw. Someone with a thread mill could likely remake the feed screw.

The table slide has a taper gib for adjustment, but once a saddle is worn in the machine ways, adjusting out play will result in binding when the slide moves off the worn area. This kind of wear is normally removed by someone experienced in manually resurfacing machine ways.

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