# SouthBend Heavy 10" Gear Train Single Tumbler Gearbox



## Frederik (Aug 5, 2020)

Hi guys,
I am having a bit of a problem, the gear train of my Soutbend Heavy 10" consists of gears to make metric threads.
The hand drawn pictures are a representation of the configuration I have on my lathe right now.

I don`t have the gears to make imperial threads. I need to make a backing plate that will fit on the spindle of the lathe.

If any of you have this exact lathe (and it needs to be the exact same model, because the gear train for the others are totally different)
would you be so kind to tell me the number of teeth each gear has. (I have included a picture of all the components I need from the Southbend manual )

These are all the components I need info on, so i can make them on the milling machine and lathe (and hopefully show you all the pictures of the manufacturing process) :

Item Nr. 79 the gear stud                         --> close up picture ?
Item Nr. 80 PRI. Pinion    --> # teeth ?     --> close up picture ?
Item Nr. 82 Stud Gear      --> 24 teeth ?
Item Nr. 88 SL. GR. Shaft                           --> close up picture ?
Item Nr. 83 Gear           --> # teeth ?
Item Nr. 97 Gear           --> # teeth ?
Item Nr. 98 Gear           --> # teeth ?
Item Nr. 100 Knob Pinion   --> # teeth ?  --> close up picture ?

I know it is a lot to ask but if you have the same model(and the time), it would be an enormous help to me if you would take the individual gears of your lathe, 
together with :
Item Nr. 79 the gear stud, 
Item Nr. 80 PRI. Pinion, 
Item Nr. 88 SL. GR. Shaft, 
Item Nr. 100 Knob Pinion 

and measure and photograph them.

That way I could make exact replicas of them. 
I am sure that many other people in the world who have the same American model and live in the metric world,
are in the same position as me, stranded...

I would be extremely grateful if anyone would take the time to make some pictures and measurements.

Another thing I am going to have to make is the Telescopic Taper Attachment(see picture).
That thing gentlemen is an absolute technical beauty.
I actually understand how it works. When I`ll build it, I`ll take pictures of it and give a tutorial on it. The kind that EVERYBODY understands.
It is a bit tricky, but when you get it, I bet you are going to think, my God that is genius !! And it is, it`s a beautiful mechanical solution to a problem.

So if you have a SouthBend Telescopic Taper Attachment, make some measurements as well (how long, how high, how wide, how much is the travel, etc.)
Let`s have some fun, everyone on this forum needs one of these, I tell you, it is brilliant !


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## Sprocket (Aug 5, 2020)

I have a SB Heavy 10, but it isn't that model. No change gears, it's all done with the two tumblers. It does have the taper attachment as in your picture, so next time I'm out there I'll see if I can get dimensions.
Doug


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## Asm109 (Aug 6, 2020)

I have a SB heavy 10 with a single tumbler gear box.  It left the factory with metric transposing gears but they disappeared long before the lathe got to me. I will measure the gears I have,  they work to cut the english threads on the chart on the front.


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## Frederik (Aug 7, 2020)

You two are absolute Angels ! Thank you so much for helping me out !

I was thinking, there are 2 ways I can approach this : I could buy several Imperial gear cutters which cost about 80 euros a piece  (and I need a lot of them) OR I could buy an entire Metric Module gear cutters set for 180 -250 euro (and I already have the arbor for them) with which I can cut all the gears and all the teeth including some extra gears I need to thread metric. (see picture SouthBendPic7)
The problem is that, I will then have to change ALL the gears including the drive gear that is on the spindle. I don`t know if the drive or spindle gear is pressed on or not. If that is the case I will be very reluctant to take it off...

I could of course leave the drive gear (40T) in Imperial, the 2 (28T) gears in Imperial and the (40T) gear beneath them in Imperial, and from then on, change all the gears that come next (24T, 127T, 100T, 72T, 18T, 80T, 30T) in Module Metric (with a 14.5 deg. tooth angle)... (see picture CurrentGears)
The 24T gear sits on top of the 40T gear, a compound gear if you will. So I could leave the 40T gear in Imperial and change the 24T in Metric Module.
The 24T gear and the 40T gear do not mesh, so it could be a possibility.

It is the gear ratios and the number of teeth that are important, not the fact that the gears are cut with an Imperial or Module cutter (providing that the Imperial gear and Module gear do not mesh), nor their respective diameters for that matter or am I wrong ?
(The diameter of a 100T Imperial gear is bigger than a 100T Module gear, or the other way around)

The pictures are drawings of the Metric transposing chart on the lathe.
There is no Imperial chart on my lathe though.

I have been tempted to take the single tumbler off the lathe and count the teeth of all the gears inside, so I could calculate mathematically what all the gears do in relationship to each other. The problem is that, I then would have to take the entire spindle head off to get at the tumbler. I don`t want to do that, because I am afraid that will give me serious alignment problems, when I put the lathe back together. Then I`ll be even further from home...


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## ajholmz (Aug 8, 2020)

First - You have a beautifully clean lathe - nice 

Second - if you're not cutting or tapping over 20 mm consider commercially available kit that supports available taps and dies that runs off the tail stock


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## HMEL (Aug 15, 2020)

I have a South Bend Lathe 9,  The gear set up is similar.  There is a book called How to Run a Lathe  South Bend Indiana 46623 I purchased it just before they closed shop.  In that book you will find the gears required for both metric and imperial threads.  It will also give you the information you need for your spindle threads so you can make a backing plate.  I will guess that you may have a lead screw with imperial thread on it.  You must take the pitch of that lead screw into account when the gears are made.  I have been looking for a set of gears that would allow me to make metric threads.  Irony of sorts you need imperial and I am looking for metric.  The other issue according to the book is the thread dial indicator is different then the imperial one.  I purchased a knock off copy some time ago for the imperial threads.  I can try and copy most the tables if you can not find the book.  Its about 5 inches in width and six inches in length and is 128 pages long.  Not sure what the quality would be if I copied it.  If you can get your hands on the book you might be better off.  It has many other details I found quite useful.  It covers all of the South Bend lathe sizes.

I also recently removed the motor and installed a variable frequency drive leaving the jack shaft and pulleys intact.  The dc control wiring and control box went where the rotary drum switch was located.  I was able to fit in an emergency stop all using low voltages switches.  The master power switch is located in a separate control box.  I really like that modification.  

I dont have all the equipment to do some of the nice work I have seen done on this forum but I am willing to share information.  I think you will really like that South Bend once you get it set up the way you like it.


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## HMEL (Aug 16, 2020)

I was able to copy some of the information in the book.  It looks like you may have an all metric lathe.
However based on what is presented here there are transposing gears that can be used for either an empirical or a  metric lathe.

Good luck.


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## Frederik (Jan 28, 2021)

Thank you HMEL for your effort to help me out, but I just need to know what the number of teeth are on all of the gears of the imperial gear train, like on the picture of the lathe above. The picture above is NOT my lathe, it is a lathe I want mine to turn into. The picture of the lathe above has all the right gears that I want to emulate. My lathe has many more gears and is completely set up to cut metric threads. I am however going to buy a book explaining how to renovate this exact lathe type. Hopefully they will show all the gears and number of teeth per gear in the drawings. If they do, I will post them on this thread, so future owners of the same lathe I have, have all the information they need to cut their own gears for imperial threading. But again I am grateful for your commitment.


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## HMEL (Jan 28, 2021)

Frederik said:


> Thank you HMEL for your effort to help me out, but I just need to know what the number of teeth are on all of the gears of the imperial gear train, like on the picture of the lathe above. The picture above is NOT my lathe, it is a lathe I want mine to turn into. The picture of the lathe above has all the right gears that I want to emulate. My lathe has many more gears and is completely set up to cut metric threads. I am however going to buy a book explaining how to renovate this exact lathe type. Hopefully they will show all the gears and number of teeth per gear in the drawings. If they do, I will post them on this thread, so future owners of the same lathe I have, have all the information they need to cut their own gears for imperial threading. But again I am grateful for your commitment.


If you look closely at the information you will see the gear (teeth count) for imperial threads using a metric lead screw.  You will need to acquire a transposing compound gear of 100/127 teeth.  I have seen transposing gears with smaller ratios but they are not as accurate.  There is also one for metric threads using an imperial lead screw.  Usually there is an idler gear to make sure the rotation is correct on the lead screw.  Sometimes a compound gear like 2/1 is used to make twice as many threads per inch but dont let this confuse you.  To calculate the gears multiply the threads per inch to be cut and the lead screw pitch by the same number.  So to cut 10 threads per inch on a lead screw with a pitch of six using a multipler of 8  we have for the lead screw  10 times 8 =80 tooth gear on the lead screw. and for the stud gear 6 times 8 or 48.  You could use different multiplers of say 5 or 7.  Not sure this is going to help but hopefully it will point you in the right direction.  All of this is in the south bend book.


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## stanstocker (Jan 29, 2021)

Greetings!  I hope these two SB pages are what you need.


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