Southbend Change Gears

[Paul LousickParticipant @paullousick59116]

(This question has been asked hundreds of times on various sites and the answers are overwhelming)

I am looking for a chart for the manual change gears on a 9″ Soutthbend (Boxford) lathe to cut metric threads.

The lathe has an 8 tpi leadscrew and I have a 47/37 tooth transposing gear.

Thread pitch required = 1.0mm, 1.25mm, 1.5mm, 2.0mm

[Speedy Builder5Participant @speedybuilder5]

Not sure about your transposing gears, page 75 from Know Your Lathe:-

[Paul LousickParticipant @paullousick59116]

A 47/37 gear has a ratio of 1.27027 instead of 1.27000 which is good enough for most applications.

This table is not in my Southbend manual and the text is a bit unclear but I think it refers to a gearbox position. My lathe does not have a gearbox.

Thanks Speedy,

[DC31kParticipant @dc31k]

Two places to look, that would be as good as definitive, are the South Bend section of Practical Machinist forum and the South Bend literature available at vintagemachinery.org

You can locate a pdf copy of ‘Know your lathe’, which will have a clear chart in it. I think the answer above is intended to point you in the correct direction rather than hand you something on a plate.

[Gerard O’TooleParticipant @gerardotoole60348]

The left chart that ‘Speedy Builder5 posted,, labelled fig. 127 shows the gears for lathes without the gearbox.

Here it is again without the other chart or text

 

[BazyleParticipant @bazyle]

The main forum for SB/Boxford is on Groups.io
https://groups.io/g/BoxfordLathe-UserGroup/topics

47/37 is not in the mainstream of conversion gears that I have heard of but if you have one does it look like a home made custom one of more match the others. Which other gears do you have? Most lathes have sets that go in steps of 5 but the SB/Boxfords use even numbers.

[Brian WoodParticipant @brianwood45127]

Paul,

I don’t have a table for Southbend , but I have calculated a generic table applicable to ALL lathes with 8 tpi leadscrews. There are no transposing gears, but a 63T gear will be needed.

Gearing layout is as follows:-

A is the driver after the reversing cluster, B the first driven gear, linked to C the onward driver for D on the leadscrew

Required 1.00   A = 30, B = 60, C = 40, D = 63       Result= 1.008 mm

Required 1.25   A = 20, B = 55, C = 65, D = 60       Result= 1.251 mm

Required 1.50   A = 30, B = 50, C = 55, D = 70       Result= 1.497 mm

Required 1.75   A = 30, B = 35, C = 45, D = 70       Result= 1.749 mm

Required 2.00   A = 40, B = 50, C = 55, D = 70       Result= 1.998 mm

I hope this helps

Regards   Brian

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