# Repairing Threads / Reading gears HELP!!!



## FDoom (Jul 31, 2013)

I obtained a South Bend 9" lathe. By the Serial number it was manufactured about 1922. I posted some pictures in another thread. Now that I have gotten a chance to really look at it. I am stumped on what to do with some of the problems. 
1) The threads to move the jaws in both the 3 and 4 jaw chucks are bad! Most of the threads in the "normal working area of the working" are broken and missing.  I am not sure How or if this can be repaired or IF the chucks must be replaced. The jaws are fine, the adjustment screw threads are good. But the inside threads are extremely bad!
2) In the pieces/parts I got with the lathe. I can't seem to find any tapered shaft that fits properly. To test the tapered bearing surface, I 'Blued up" a drill chuck with the tapered shank I thought to be correct. BUT, when I inserted the drill chuck and twisted it to get bearing marks in the tail stock. The drill chuck only shows a ring around the very front ot the taper next to the chuck. Any bearing marks except a single ring near the opening. The taper in the Head and Tail stocks appear to be the same. Next step I will try is to measure the taper. 
3) I am stumped at how to change cutting feeds with the gears I have. I am really confused about gear ratios and gear placement for the gears I have. In the 2nd attachment picture, There is a small diagram. But it is very hard for me to read. 
4) As you can see in one of the pictures the gear on the far left side has "54" stamped into it.  Do I count the teeth on each gear?  Some of the gears on the lathe and some of the "extra" gears have numbers stamped onto the sides. I am hoping this will help, but I'm not sure how. ANY information would be greatly Appreciated.

Doom!


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## wa5cab (Jul 31, 2013)

Doom,

It's difficult to say without photographs, but from your description of the chucks, unless you luck into the same ones cheap and can use two to make one, you may have to replace them entirely.

On the gear questions, the numbers stamped on the gears should be the tooth count.  The numbers on the chart, except for the FIG and decimal ones, are tooth count.  

Having said that, I'm not personally familiar with SB lathes and what I can see of the threading chart I don't understand, either.  Fig 4 shows 5 gears with tooth count, but the chart only lists 3 or 2.  Maybe if I could see the entire chart, I could decipher it.

Robert D.


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## GK1918 (Jul 31, 2013)

As far as the chuck, thats anybodys guess, by now I'd shop for a new or better one, (which is like car tires) they wear, thats not a problem. Problem is you have to take a good look at the chart, its all there in the chart. If you post a full picture of the chart we can help. The concern is the combination of these gears to obtain the feed you want on the right side of the chart.  All this is online can't remember, could be south bend site I got it saved and will 
look for it.  Although change gear models a little annoying but gets the job done when understood.  I will look sam


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## martik777 (Jul 31, 2013)

This any clearer? Most of the common threads, except 32tpi, are covered by Fig2, so you just need to change the stud and screw gears and leave the 80T idler in place.  I hope you have the gear cover, if not, make something - very dangerous without. 

Here is the catalog and specs for your model: http://www.wswells.com/data/catalog/1935_catalog_15-W/1935_catalog__15-W.pdf   It says MT2 for head and tail but I don't understand how the MT2 works with a 3/4" thru hole in the spindle.

Couple more links:

http://www.stingersplace.com/lathe/

http://www.lathes.co.uk/southbend9-inch/

DO you have some pictures of the chucks?


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## wa5cab (Aug 1, 2013)

Ahh.  Seeing the complete chart, I can see that the approach to the whole matter is different from what it is on the various size Atlas machines, which I'm familiar with.  The gears shown in a single Figure are always the same and the Stud gear and Screw gear change.  Instead of the other way around.

Robert D.


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## Tillerman6 (Oct 6, 2014)

It looks like you have some of your answer.  The nice gear chart in the thread tells you the gears required for the various feeds per inch.  You'd have to do some math to find the combinations that would give you some useable threading pitches, but basically a 1/4-20 machine screw is cut with 20 threads per inch which works out to 1.00 divided by 20 or .050".  So if you can throw some gears on your machine that give you that pitch, you can cut any diameter of bolt that uses 20 threads per inch and so on.  The thread chart on your machine does not spell it out for you, but that's one way to go about it.  

If you're looking to put a fine surface on a rod or tube, you want something more like 0.002" per revolution which is called "fine feed".

Maybe you could look for a book called "how to run a lathe" by South Bend lathe company. These are out of print, but can still be found on Ebay and should really help you out way beyond your questions on here.

As far as the scroll part of your chucks, they would be pretty difficult to fix.  the scrolls are cast iron and usually the only thing that will stick to that is bronze or brazing material.  If you were super patient and were good with a Dremel tool you MIGHT get lucky and be able to carve the missing parts of the scroll, but personally I don't know if it would be worth your time and effort, considering that you can get some workable 3 jaw chucks with a backing plate for something under 100.00 used on Ebay.


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## mainspring (Nov 5, 2014)

Doom,

     Toss the chucks! Not worth it. IMHO best cheap chucks are from Bison. The broken chuck screws indicate some doofus
      with a pipe cheater has had at them. Send them back to the furnace.
      Tail stock spindle: Number 2 Morse taper, I presume. Buy or borrow a #2 taper reamer, and give it 1 or 2 twists
      in the tailstock taper bore. See it contact improves. If you ream the spindle too deep, you'll be constantly bumping
      the chuck out of it when you withdraw a drill. Then it's new tailstock spindle time!

       Bad tooling is worse than No tooling!


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