Southbend 127 teeth gear

[hermesj]

I have recently purchased a 9" (8TPI) Southbend lathe and ran into a little unexpected problem. I wanted to copy a thread and realized that it was metric. no matter how hard I tried to chase the thread, I could not match it with my gears.
I understand that I need a 127 teeth gear and wonder just where I might get something like that.

Thanks for your help. Jurgen

[Steven L Jones]

<font face="Verdana, Arial" size="2">Originally posted by hermesj:
I have recently purchased a 9" (8TPI) Southbend lathe and ran into a little unexpected problem. I wanted to copy a thread and realized that it was metric. no matter how hard I tried to chase the thread, I could not match it with my gears.
I understand that I need a 127 teeth gear and wonder just where I might get something like that.

Thanks for your help. Jurgen</font>

I thought you might find my venture in the metric thread cutting interesting interesting . I have an old south bend lathe made in the early 19 something. about 2 years ago I decided that i needed a 127 tooth translating gear .I have made several gears for the change gear collection .so i decided to attempt to make this one also.first i needed a blank 9.214 . which i found a torch burnout about3 in too big and rough as a cob.but managed to get the blank made on my old lathe. i have a dividing head .so I figured no problem .Next I made an arbor to hold the blank . got set up in my milling machine. then proceeded to start indexing, as it required the compound indexing. method i wanted to just barely scratch the blank with the cutter just to make sure that the indexing would be correct . well ,I tried 6 times to get around that blank correctly . finnaly I gave up on that. just too many moves for me. so i took the blank out an set it aside . In the meantime I decided to subscribe to the home shop machinist magazine, and what to my wondering eyes should appear in the Jan-Feb issue but an article on a wonderous idea for a 100 division indexing plate to solve all problems,(grin)Just this evening I completed that project.Will rest up and give the gear blank another try. so have fun surely some one has that gear for sale.

[SGW]

Something that might be easier: It turns out that a 47/37 gear combination is *very* close to 127/100, and may be easier/cheaper to get.
It will certainly be close enough for anything you're likely to do.

[artificer in metal]

If you plan on making only Class 1 threads an approximation will do - otherwise I wouldn't bother. It is tough enough to make a nice class 3 without having lateral inaccuracies.

[SGW]

We're talking about an error of about .0002" per inch. "Close enough for all practical purposes."

[roberlt]

Check out "A claytons change wheel" bw Terry Sexton PIM Dec 1998.
Rob