# 9" south bend



## Kernbigo (Jan 17, 2014)

I have a 9" south bend wide bed, they use 1/2" face boston gears some of the bores are 5/8" and some are 3/4" depending where you put them. Dos any one know what came with the lathe as a set of change gears? For now just want the change gears and later on the thread gears.


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## tonylathes (Jan 18, 2014)

Kernbigo said:


> I have a 9" south bend wide bed, they use 1/2" face boston gears some of the bores are 5/8" and some are 3/4" depending where you put them. Dos any one know what came with the lathe as a set of change gears? For now just want the change gears and later on the thread gears.



Here is the screwcutting data you need: 

All South Bend 9-inch changewheels are 18 D.P. with a 14.5-degree pressure angle and a 0.125" depth of tooth. They are 3/8" wide.have a 9/16" bore, a 1/8" keyway. 
The idler and compound gears (two gears on one shaft) are different: they have have a 5/8" bore with no keyway and are fitted to a hardened bush held in place with a through bolt. 

Model C 
"English" threading lathes with an 8-tpi leadscrew and changewheels for screwcutting (i.e. without a screwcutting Gearbox) were supplied with the following changewheels as standard: 
*16 (stud gear on tumble-reverse output), 24, 36, 40, 44, 46, 48, 52, 54, 56, 60, *80,  *72/18 compound,  *80 idler (with boss)
(* Gears fitted on the lathe as dispatched from factory for standard feeds and as shown on page 60 of the manual)
To convert a non-gearbox English-specification lathe to cut metric threads the following gears are needed: 
20, 100, 127/100 combination
In addition, to cut the following five pitches extra gears are required as follows: 
0.45 mm = 18t gear
0.55 mm = 22t gear
0.65 mm = 26t gear 
0.7 mm and 3.5 mm = 28t gear

************************************************
Model C
Metric threading lathes with a mm pitch leadscrew and changewheels for screwcutting (i.e. without a screwcutting gearbox): were supplied with the following gears as standard:
 *16 (stud gear on tumble-reverse output), 24, 28, 30, 36, 40, 44, 48, 52, 56, 60,  *80,  *72/18 compound,  *54/18 compound,  *80 idler (with boss).
(* Gears on machine as dispatched from factory for standard feeds)

To convert a non-gearbox Metric-leadscrew lathe to cut English threads the following gears are needed: 
18, 22, 26, 38, 54, 64, 88, 135/127 compound, 48/24 compound.

127/135t compound gear (Metric to English conversion):
48/24t compound gear: 
18t 
22t 
26t 
38t 
54t
64t 
88t

"English" threading lathes with a screwcutting gearbox had a standard ex-factory drive train consisting of: 
20t, 40t, 56t and an 80t idler.
Fitted with these gears the full range of threads as shown on the front of the gearbox can be generated.
To convert this gearbox to cut a full range of Metric threads the following gears are needed: 24, 26, 28, 32, 36, 44, 48, 127/100 compound

************************************************
Metric threading lathes with a screwcutting gearbox had a standard ex-factory drive train consisting of: 
20t, 45t, 50t and an 80t idler. Fitted with these gears the full range of threads as shown on the front of the gearbox can be generated.
To convert this gearbox to cut English threads the following gears are needed: 
38, 40, 44, 52, 56, and a 135/127 compound

My best wishes,

Tony. 
lathes.co.uk


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## stevecmo (Jan 18, 2014)

Welcome, Tony!


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## Kernbigo (Jan 18, 2014)

Thanks much for the information. My lathe is a 1937 wide bed r series, and it takes boston gears 16dp 1/2" face and 5/8" bore so i 'am not sure what they supplied with that lathe will be the same for change gears?


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## mrflashlite (Jan 18, 2014)

Hi Tony I know that the thread started out asking about the 1937 9" wide bed, but I was told that my 1927 9" south bend jr used change gears that were 1/2" face, 5/8"bore but they used a 16 D.P. Do you know if this is correct and if it is would it use the same set as below only with the 16 D.P., also do you know if they are the 14.5 pressure angle.




tonylathes said:


> Here is the screwcutting data you need:
> 
> All South Bend 9-inch changewheels are 18 D.P. with a 14.5-degree pressure angle and a 0.125" depth of tooth. They are 3/8" wide.have a 9/16" bore, a 1/8" keyway.
> The idler and compound gears (two gears on one shaft) are different: they have have a 5/8" bore with no keyway and are fitted to a hardened bush held in place with a through bolt.
> ...


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## Kernbigo (Jan 19, 2014)

I know if yours are 16dp like mine the pressure angle is 14 1/2 degree, now to find out if what was sent with that machine is the same as the ones with 18dp?  Also is the gear chart going to be different which seems like it would for sure?


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