Dr. Hillbilly
Aluminum
- Joined
- Dec 6, 2019
- Location
- Oregonia, Ohio
As I slowly learn about vintage machining practice I realize that I have been inquiring about an index head for hobbing, when I do not need an index head at all, and I am once again sabotaging my searches with incorrect terms. (I need a Rosetta Stone to translate from CNC to Vint.!)
If I hob a worm gear there is no table motion at all, so rotation of the gear must be driven by the spindle (a gear set from the outboard end of the arbor?).
Helical and spur gears will require table motion for hobbing, but the the traverse rate is very slow. For example if I am hobbing a 20 tooth gear with a single tooth hob my spindle speed must be 20 times the table speed. So if the hob is turning 100 rpm the table must turn 5 rpm. If an index head with a 40:1 reduction ratio is used then the input shaft must be turning 5X40= 200 rpm. Gearing the slow rotation of table up to 200 rpm seems problematic.
So were simple tables without index plates or reduction worms ever used?
Was outboard arbor drive of the table every pursued?
How common was it to use the hob to drive the head, so there is no head drive from the table or the spindle?
If I hob a worm gear there is no table motion at all, so rotation of the gear must be driven by the spindle (a gear set from the outboard end of the arbor?).
Helical and spur gears will require table motion for hobbing, but the the traverse rate is very slow. For example if I am hobbing a 20 tooth gear with a single tooth hob my spindle speed must be 20 times the table speed. So if the hob is turning 100 rpm the table must turn 5 rpm. If an index head with a 40:1 reduction ratio is used then the input shaft must be turning 5X40= 200 rpm. Gearing the slow rotation of table up to 200 rpm seems problematic.
So were simple tables without index plates or reduction worms ever used?
Was outboard arbor drive of the table every pursued?
How common was it to use the hob to drive the head, so there is no head drive from the table or the spindle?