I purchased my South bend lathe at an auction perhaps 30 years ago. Have chased a bazillion standard threads,but when attempting to produce a template for checking an internal thread for the standard 8" chuck thread on my lathe, I ran into the problem of a thread that is not standard. I believe the gearing is off somewhat, due to perhaps a wrong combination of gears installed on the lathe prior to the auction. This was used in, I believe, a technical school training facility associated with the former Norfolk, VA, College of William and Mary extension.
So if there have not been other modifications to the double tumbler gearbox, what are the proper gears for the spindle driven gear train which drives the input to the double tumbler Gearbox? I suspect that there were some gear substitutions that don't follow the data as listed on the gearbox for setting up to cut threads. I had never had a need to chase an 8 T.P.I. mandrel until recently. I then discovered that what I hoped were the right threads were about a .032 wider spaced than hoped for. I have played around with gear changes with the gears available, and nothing seems to work for the thread I am attempting to machine.
I have looked through all sorts of South Bend literature, but nowhere have I seen a layout of the gear sizes required to produce what I am attempting to chase on the lathe. It would appear that there are one or more gears that did not come with the machine when purchased that will give me the desired results. If anyone has a diagram that states number of teeth in each gear in the assembly, it would be a great help.
The South Bend parts catalog only state gear numbers etc. For the most part the catalog does not include the number of gear teeth on those gears.
So if there have not been other modifications to the double tumbler gearbox, what are the proper gears for the spindle driven gear train which drives the input to the double tumbler Gearbox? I suspect that there were some gear substitutions that don't follow the data as listed on the gearbox for setting up to cut threads. I had never had a need to chase an 8 T.P.I. mandrel until recently. I then discovered that what I hoped were the right threads were about a .032 wider spaced than hoped for. I have played around with gear changes with the gears available, and nothing seems to work for the thread I am attempting to machine.
I have looked through all sorts of South Bend literature, but nowhere have I seen a layout of the gear sizes required to produce what I am attempting to chase on the lathe. It would appear that there are one or more gears that did not come with the machine when purchased that will give me the desired results. If anyone has a diagram that states number of teeth in each gear in the assembly, it would be a great help.
The South Bend parts catalog only state gear numbers etc. For the most part the catalog does not include the number of gear teeth on those gears.
