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South Bend 13 lathe - 19tpi

Brannigan

Plastic
Joined
Jan 8, 2018
Does any wise person know which non-standard stud gear can be used on single tumbler, South Bend 13" lathe, from around 1940? Unfortunately the banjo does not allow for any change gears... Currently got a second lathe clogging up my workshop just to cut 19tpi as it's a common English thread. Also hoping to get 100% thread accuracy and maintain use of the thread dial. If not possible, reckon I'll have to go down the route of making a new banjo that will allow alternate change gears between the stud gear and gearbox.

All thoughts much appreciated - thanks!
 

johnoder

Diamond
Joined
Jul 16, 2004
Location
Houston, TX USA
All thoughts much appreciated
Get down to basics - like the over all ratio compared to the 6 TPI lead screw

20 TPI is 3 1/3 to 1 (.16666 / .050 )

19 TPI is very close to 3 1/6 to 1 (.16666 / .05263 )

And work from there to come up with tooth count
 

TGTool

Titanium
Joined
Sep 22, 2006
Location
Stillwater, Oklahoma
I think there's not enough information in your original question for anyone to develop real suggestions. It would help to know how many teeth in the stud gear now. Also, we can only presume the machine has a QC gearbox with some thread choices not including 19.

First, there's no likely stud gear possible for just a quick change from 20 to 19. That would require a fractional tooth number unless it happened to be 20 teeth now and you could replace it with a 19 tooth. If your QC has an option for 38 teeth, you could install a stud gear with half the teeth it has now, not very likely.

You're probably up against getting or making a banjo that lets you make more gear choices.
 

SBLatheman

Titanium
Joined
Jul 7, 2008
Location
South Bend, In
I don’t know if you can read this document….
It says that the closest you can get is 19.019 TPI with a special stud gear (53 teeth)
That’s .00005 error in lead.
Ted

After previewing the picture…it is hard to read
 

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Brannigan

Plastic
Joined
Jan 8, 2018
I don’t know if you can read this document….
It says that the closest you can get is 19.019 TPI with a special stud gear (53 teeth)
That’s .00005 error in lead.
Ted

After previewing the picture…it is hard to read

Hi SBlatheman, thank you for this. Any idea where I can find a readable copy of this document? Looks useful. Thank you!
 








 
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