# How would I Convert SB9"B" to model "A" with quick change gear box?



## xalky

I would like to convert my 1938 southbend 9 model B to a model A with the quick change gearbox. Does anyone know of a write up to do this conversion?

Here's a picture of my current lathe.




I would like it to be like this.

http://www.hobby-machinist.com/attachment.php?attachmentid=40282&d=1347326689


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## Bill Gruby

There are some links here in another thread about the same conversion.

http://www.hobby-machinist.com/show...l-quot-B-quot-conversion-to-Model-quot-A-quot


  "Billy G" :thinking:


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## xalky

Hey Thanks Bill. I didn't realize I had to change the apron too. And then there's the issue of the "0" dial which my lathe does not have and neither does the one in the second photo I posted..I think? If I could find a good parts donor machine it would be worth doing but I'm not sure I want to invest a lot of money in this small lathe. I paid $100 for it and probably put another $400 in it for a chuck, AXA tool post and a better motor. I've been looking for a good 12" or 13"  x 4-5' lathe with a quick change for a while, but nothing has turned up yet.

Bill, We're practically neighbors. I'm up your way all the time.

Marcel


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## Bill Gruby

I just noticed that, we are neighbors (almost). 

 "Billy G" :thumbsup:


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## Hawkeye

The link Bill posted was for a C to A. Yours would be similar, but the apron should be the same between B and A. The gearbox info is what you need.

There appears to be a typo in the 'required parts' list for converting a C. It says you need an A or a C apron, but I'm sure you need an A or a B apron, so you're good.


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## joebiplane

xalky said:


> Hey Thanks Bill. I didn't realize I had to change the apron too. And then there's the issue of the "0" dial which my lathe does not have and neither does the one in the second photo I posted..I think? If I could find a good parts donor machine it would be worth doing but I'm not sure I want to invest a lot of money in this small lathe. I paid $100 for it and probably put another $400 in it for a chuck, AXA tool post and a better motor. I've been looking for a good 12" or 13"  x 4-5' lathe with a quick change for a while, but nothing has turned up yet.
> 
> I didn't have to change the apron on my B  to ecome an "A".... get the box and a leadscrew from another "A" with the same bed length your bed is.
> you will also need the 20 and 56 tooth syud gears that an "A" model requires  and the gear for the leadscrew that will reside in the gearbox on the end of your leadscrew.
> If you want , pplease feel free to contact me via e-mail   joe@oldetimemachines.com
> joe


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## Boot

I did the conversion of my SB9 last year.  Only trouble I had was putting the counterbore in the hardened V way.  I got it mostly in and then had to use a Dremel to grind it larger.  I was lucky enough to buy the QC gearbox, keywayed lead screw and the small I think 20t gear.  I did not want the cross feed to work ,but I needed an easier way to thread than the changing of gears provided. It works great. I have a homemade thread dial and it is great also.  I did 2 jobs on it and I have to make a new shank for my boring head.  I tried turning the shank  down that's in it and I didn't quite get it running "0" .  I must now unscrew it and turn and thread a new one between centers.  I only paid $125 for my gear box and it's in perfect shape.  I used the instructions given in a pdf file that you have access to.  Good luck to you, Boot


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## pjf134

The apron on the pic does not have a power feed selector lever or a clutch knob, just a half nut lever. It looks like a change gear type or "C" type if you perfer. So for power feed you would need a apron. See my 9A pic.
Paul


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## Hawkeye

I missed that too, Paul. That is a C.


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## joebiplane

xalky said:


> I would like to convert my 1938 southbend 9 model B to a model A with the quick change gearbox. Does anyone know of a write up to do this conversion?
> 
> Marcel,
> 
> I did the conversion and it was simple...just follow the advice you have been given in this thread.
> get the gear box,  the proper leadscrew, the required gears and put it together.
> 
> On my conversion i was perplexed with the binding of the lead screw until I realized that if the machine was to be a Model "A"  the factory properly *aligned the lead screw *with the *lathe  bed rack*
> I had to slightly shim the QCGB to get the screw in alignment and then All was well....simple matter once you know the problem.
> 
> you may not need to do this but if you have a problem once you tighten the screws on the QCGB to attach it to the bed....you know what it might be.    Don't turn on the machine untill it works smoothly after it is all set up.  Good luck and you will love it !
> joe


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## xalky

I'd love to do it, but finding the parts at the right price are the challenge. I really don't want to spend more than $300 for the whole shooting match, apron, QC, lead screw, etc. Which i know is a tall order. I'll just keep my eyes open and wait.


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## Boot

I converted my model C to an A by following those instructions given you.  I bought a QCGB and lead screw for mine and that was all it took.  Drilling the hole for the extra hole to hold the QCGB was aided by the use of my Dremel grinder.  I didn't have the right size counterbore so I improvised with a drill I ground for the job.  It didn't quite make the hole the right size so I had to Dremel it out a little. The QCGB I got works great. I didn't change the apron on the machine because I don't do that much facing with my machine. Boot


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## xalky

Don't you need the apron for the thread dial? Or is there a way to improvise a thread dial, you know the one that comes around to time your reengagement.

In the past, when threading, I could not disengage the half nut or I would lose my place. 

So the procedure would be to take the first pass, stop the machine, back off the tool, reverse the machine by hand back to the beginning, feed in tool, start second pass. A major PITA.

I think that's worse than having to change the gear sets. Actually i would rather have to change the gear sets than futz with that procedure to produce a thread. I've done it, but its tedious.


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## Boot

All aprons have a hole already drilled in them to accept a thread dial.  Also a tapped hole to put a set screw in to hold the thread dial either engaged with the lead screw or disengaged from the lead screw.  The thread dial is the the only way that is easy to thread parts. In our machine shop we always used even numbers on the thread dial for even numbered threads "ie. 16, 12, 6, 8 / inch and odd numbers on dial for odd number of threads on part "ie 13, 11, 11 1/2 and so forth .  Try it you'll like it. Hope this answers your question.    Boot.


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## xalky

The thread dial would make life a lot easier. Changing the gears aint quite so bad. 

OK, so where can i get a thread dial? Is it a southbend part or are there generic ones i can buy?  This is all new to me.

Marcel


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## xalky

The thread dial would make life a lot easier. Changing the gears aint quite so bad. 

OK, so where can i get a thread dial? Is it a southbend part or are there generic ones i can buy?  This is all new to me.


EDIT: http://www.ebay.com/itm/NEW-THREAD-...424?pt=LH_DefaultDomain_0&hash=item20ce0ba640  I just spotted the hole on my apron. So if I just get one of these, I should be golden. Right?

Marcel

EDIT again: I just ordered the thread dial. This is exciting. )


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## joebiplane

pjf134 said:


> The apron on the pic does not have a power feed selector lever or a clutch knob, just a half nut lever. It looks like a change gear type or "C" type if you perfer. So for power feed you would need a apron. See my 9A pic.
> Paul



i am old but the blue lathe i see in the photo has a clutch knob and a power feed selecter

Am i missing something ?????


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