# Spindle Adapter



## Ken S (Jul 11, 2016)

I recently acquired a dividing head at the Grizzly tool sale in Springfield. I would like to use my lathe chuck on it but my lathe spindle is larger than the dividing head spindle. I thought about making a bushing  but my threading skills aren't too good yet and I'll need to make a boring bar. I haven't tried to thread internally yet so I expect I'll making more than one of these before I get it right.
My question for you guys is, will a bushing work (assuming I get it threaded right) or should I just forget it and buy a another chuck? I don't want to end up with something that might never be accurate but I'm cheap enough and dumb enough to try it.

The dividing head had a threaded backplate that I could turn to fit my lathe chuck but the one in the chuck now is pressed in and something tells me it's a bad idea to try to continually press these in and out of the chuck every time I want to use the dividing head. I'm not that cheap.

Ken


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## Wreck™Wreck (Jul 11, 2016)

Thread the ID and OD  and faces in the same setup and it will be as concentric as possible.


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## 4GSR (Jul 11, 2016)

There are several threads on this very subject on H-M.  Do a little searching and reading.  This is where you need to get your feet wet.  There are several varieties of boring bars out there to consider buying.  Rather is is an insert type of boring bar or one that accepts "square" shank tool bits, they are out there.  Since Grizzly is near you go do some shopping for tooling.  Also look for a insert boring bar that holds a threading insert so you can cut threads with.  Grizzly show them in their catalog and they should have them in stock at Springfield.
Feel free to ask more questions if you need help, that's what we are here for.


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## Ken S (Jul 12, 2016)

Thanks guys, I searched for an answer to this question before I posted this and found nothing and just tried again with no results. Maybe I'm asking the wrong question. I really just want some assurance that using a bushing to fit a chuck to a smaller spindle is something that is commonly done and does work out well.


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## 4GSR (Jul 12, 2016)

We call them back plates.  The word "bushing" maybe confusing many of us. But that's ok, you're learning.  And yes, this is commonly done and standard with most chucks out there.  Try searching using the word "back plate" and see if you get something.  If still no luck, let us know.  Ken


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## Ken S (Jul 12, 2016)

4gsr said:


> We call them back plates.  The word "bushing" maybe confusing many of us. But that's ok, you're learning.  And yes, this is commonly done and standard with most chucks out there.  Try searching using the word "back plate" and see if you get something.  If still no luck, let us know.  Ken[/QUO
> 
> 
> Thanks Ken, I found the posts.


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## Ken S (Jul 12, 2016)

Please don't slap me around for this but I still don't find anything related to my question. I found these adapter bushings on e-bay that are sold for wood lathes. I just can't find one for metal lathes and that is why I'm questioning whether it is done on metalworking machinery. I know I can eventually produce a bushing to fit but I want to know if others have done it and if there is any loss of precision through the use of a bushing.

http://www.ebay.com/itm/PSI-Woodwor...le-Adapter-for-a-1-Inch-by-8TPI-/152133924119

There was a threaded back plate that came on the dividing head but what I read says it needs to be turned for a press fit. I would rather be able to use a bushing than have to press back plates out and in  every time I want to use my chuck on the dividing head.  It seems doable to spin my chuck off the lathe spindle, insert threaded reducer bushing, and spin it on the dividing head spindle.


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## Billh50 (Jul 12, 2016)

Ken,
As long as the threads are a close fit and any shoulders are square to both you should be ok.


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## Randall Marx (Jul 12, 2016)

Hi Ken
I think I understand what you are trying to find and accomplish. Yes, this is quite doable and should be a good solution if made accurately.
In order to make the bushing/adapter as accurate as possible, using some form of a sequence of operations is necessary. If you read through the various descriptions about making back plates, you should notice a pattern. The first thing done is to get the rough stock mounted as concentric as possible, followed by facing, drilling, boring, and threading the spindle hole as necessary to thread onto the lathe spindle, all in one setup. Then, thread the adapter onto the spindle just as it will be used once completed. With it mounted this way, you can perform any operations needed to make it fit the chuck and the resulting work will be as accurate as your lathe is capable of producing.
Provided that you get good fits in each step, you should get a good overall result in mounting your chuck.
By the way, this is called the friendly machinist forum for a reason. We like to help each other and will NOT slap you around for asking questions and trying to understand what you are doing.
Good luck and if anything is unclear, just ask!


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## Ken S (Jul 12, 2016)

Billh50 said:


> Ken,
> As long as the threads are a close fit and any shoulders are square to both you should be ok.



Thank you Bill


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## 4GSR (Jul 12, 2016)

I now see what you are talking about.  I've never ran across using one of these.  As Bill said, if it's all good and square and running true it should work.
Sorry for the confusion.  Learn something new today.


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## Andre (Jul 12, 2016)

On wood lathe chucks (Nova, and on my 4 jaw scroll chuck made by WoodRiver) they use a large chuck ID thread and use replaceable threaded bushing inserts so you buy the correct one to fit your lathe. My wood lathe has a 1"-8 thread, but many use 1 1/2-8"  spindle threads, and some older Walker Turner lathe have a 1"-11 thread. 

At least on a wood lathe, the inserts work well. On both threaded surfaces the alignment is controlled by shoulders (per usual), not thread fit. In case you were curious


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## Ken S (Jul 12, 2016)

Thank you Randall, This forum has been great and I usually can find an answer without posting a question.
I guess I've been conditioned from being part of other groups to expect some impatience and ridicule from the more experienced. The world is getting less and less patient and encouraging but I certainly have not seen that here and I apologize for even anticipating it. You guys deserve better.
Thanks again


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## Ken S (Jul 12, 2016)

Thanks for jumping in to help Ken


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## Ken S (Jul 12, 2016)

Andre said:


> On wood lathe chucks (Nova, and on my 4 jaw scroll chuck made by WoodRiver) they use a large chuck ID thread and use replaceable threaded bushing inserts so you buy the correct one to fit your lathe. My wood lathe has a 1"-8 thread, but many use 1 1/2-8"  spindle threads, and some older Walker Turner lathe have a 1"-11 thread.
> 
> At least on a wood lathe, the inserts work well. On both threaded surfaces the alignment is controlled by shoulders (per usual), not thread fit. In case you were curious




Andre,
Yes, I was wondering if the shoulder would maybe forgive the imperfections of my work. That's good to know. My lathe spindle is right at 2" and I wasn't able to find a bushing over 1-1/2. I think I'm gonna cinch up my big bot pants and try to expand my skill set on this one.


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## Randall Marx (Jul 12, 2016)

If I may, I would like to suggest practicing on a plastic type of material to hone your skill if you are unsure about single-pointing threads. The material might be less expensive and is surely more forgiving of something like a crash. I've used that in the past to good effect. Again, good luck!


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## Andre (Jul 12, 2016)

Ken S said:


> Andre,
> Yes, I was wondering if the shoulder would maybe forgive the imperfections of my work. That's good to know. My lathe spindle is right at 2" and I wasn't able to find a bushing over 1-1/2. I think I'm gonna cinch up my big bot pants and try to expand my skill set on this one.



Threads just hold the piece on, it's the shoulder that aligns everything. Make sure you add a small relief where the thread meets the shoulder. A radius or where the thread tapers off can prevent the shoulders sitting right and possibly causing a misalignment.


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## 4GSR (Jul 12, 2016)

I don't know about other lathes out there, on my 9" South Bend lathe, it has 1-1/2-8 thread spindle.  And at the back end of the thread next to the shoulder, is a OD turn that is about 1.504" in diameter by about 3/16" long.  This is done so you machine a small counterbore about 1/4" deep x 1.505" diameter in the adapter or backplate. Doing this creates a register for the chuck back plate or adapter to locate on along with the face of the shoulder of the spindle when made up.


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## Ken S (Jul 12, 2016)

Ken, I had to read that several times before I understood it. Interesting 
I'll have to look at the back plate on mine to see if it's the same. 
Thanks


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## Billh50 (Jul 13, 2016)

4gsr is right about the shoulder on the spindle. The shoulder is usually what will make the chuck run concentric with the spindle. The back face makes it run square to the spindle.


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## Ken S (Jul 13, 2016)

There isn't a collar on my lathe spindle. It's a step shaft but the OD is larger the the back plate bore. There is, however a collar on the dividing head spindle that looks like it would make a good register inside the bushing. I'm stopping down from 2-14" to 1-1/2 with 1-5/8 collar. That should work out real good. 
Thanks for all the advice and info.


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## Ken S (Jul 13, 2016)

2-1/4


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