irby - thanks so much for posting those patent pictures. I had to leave town for business early this morning so I didn't have a chance to do that. I've got everything off the index plate side and have the clamping bolts removed. Unfortunately I will not be able to get back to this for a few days - but keep the ideas coming.
Thanks
Rick
Hey Rick, I read over the entire the patent on your dividing head. I'm interested in the workings of old dividing heads because I have one myself (a Garvin universal) that I will clean up and restore some day. Turns out that removing the worm-shaft "J" is very easy. Here is what the patent says about it (you have to refer to the patent drawings for all the part nomenclature):
"For rapid indexing or such work as milling reamers, taps, nuts, etc., and cutting spur wheels with less than forty teeth the worm-shaft is disengaged from the worm-wheel and a hand index-wheel U, Fig. 4, is employed. To remove the worm-shaft, it is only necessary to swing the spindle with its work-holding end down to the vertical position shown by the solid lines, Fig. 9, when the worm-shaft will register exactly with an opening c’ in the plate c. By now rotating the spindle to the left the worm-shaft will be ejected through the opening c', and can be laid aside until again wanted. It is inserted in a similar manner by rotating the spindle to the right. As the spindle is never used for work when set vertically in this position - that is, with its working end down - there is no danger of the accidental displacement of the worm-shaft, as it is always at other times held locked in place by the plate c."
The description above says Fig 9, but it's really Fig 10. And the opening "c’" is the big hole in the side plate.
The worm-shaft, collar "o", and the split nut "p" screwed onto the collar, all come out as a unit, shown in the picture below. Once out, the spindle can be removed by unscrewing the hollow plug "n" from the body "G", then pushing the spindle out. It appears in Fig 4 that the teeth of the worm wheel "I" are cut so that they curve around the teeth of the worm-shaft "J", preventing the spindle from being removed unless the worm-shaft is out.
The worm-shaft "J" to collar "o" fit is adjusted with the split nut "r" so that the worm-shaft turns in the collar but has no end play. Then the nut "r" is locked in position by screw "s". If this works like other split nut locking schemes I've worked on, tightening the locking screw changes the settings a little, so you have to iterate on the adjustments some.
The worm-shaft itself rotates on one end in a plug "t’" which is captured by the side plate "b" of the base. The other end rotates in the collar "o" which fits into a counterbore in the body "G" and is captured by the side plate "c". The fit of the worm-shaft "J" to the spindle worm-wheel "I" is set by adjusting the split nut "p" so that the spindle can rotate but there is a minimum of slop between the worm-shaft and the worm-wheel. The lateral position of the worm-shaft, and therefore the clearance between the worm-shaft and the worm-wheel, is set by the position of the split nut "p" on the collar "o" - how far the nut is screwed or unscrewed onto the collar. That adjustment is made when the collar "o" and it's locking screw "q" are visible in the side plate hole "c’". To keep the collar "o" in it's correct position in the body during this adjustment, you probably have to rotate the body "G" slightly so the collar is captured by the side plate and you still have access to adjust and lock the split nut.
One end of the worm-shaft fits into a gear "t" that meshes with a gear "u" on the indexing system, and serves to rotate the worm-shaft. The gear "t" is captured in the body "G" by the plug "t’" which is also the end bearing for the worm-shaft. Apparently the plug "t’" is only accessible when the body "G" is out of the side plates. It looks like there is a key or something between the far end of the worm-shaft and the gear. When putting the worm-shaft assembly back into the body, I guess you would have to rotate the gear by turning the indexing system so that the key lines up and engages.
Worm-shaft and collar when removed:
Hopefully I'm close to what this dividing head is really like in what I infer from the patent drawings and description. Sounds like fun working on it!
Irby