# Why Threaded Spindle Bore?



## Tozguy (Dec 18, 2015)

My new lathe came with female threads in the outboard end of the spindle. The inboard end of the spindle is D1-4 with an MT5 taper in the bore. The threads in question are 16 tip and go roughly 1,5'' down the bore and finish at a small shoulder.This detail was not mentioned in the specs for the lathe and I have not seen anything since that would explain why they are provided.
Is this a common feature for lathes and what do you folks actually use them for?


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## stupoty (Dec 18, 2015)

maybe for a "spider" or other lose collet to hold the free end of long bars put through the spindle.

Stuart


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## RJSakowski (Dec 18, 2015)

I threaded mine for a work stop. http://www.hobby-machinist.com/threads/lathe-headstock-work-stop-g0602.32809/

Bob


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## tomh (Dec 18, 2015)

It is common for spindles to be threaded on the out board side with threads on the out side or inside for attachments such as collets and spiders etc. Most people  don't  pay much attention as they rarely look at that end unless they are adjusting bearings  or changing gears etc.  Some makers will  leave the threads  on the OD to the end of the spindle others will not.   Having worked on many lathe over the years I have seen many variations.
Tomh


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## Ebel440 (Dec 18, 2015)

A long tube with male threads goes in to support long material hanging out the spindle


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## Bob Korves (Dec 18, 2015)

Tozguy said:


> (snip)
> Is this a common feature for lathes and what do you folks actually use them for?


Some lathes have it, some do not.  Use it for whatever you wish, it is your lathe.  Common uses already suggested above.  Be creative, with your lathe you can make whatever suits your needs and wants.  Just try not to do something dangerous...


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## RJSakowski (Dec 18, 2015)

Another use would be a hand crank to "jog" the spindle or for threading with a tap or die.


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## Ebel440 (Dec 18, 2015)

If you make the tube don't make it too long or it will bend. The purpose of it is to prevent thinner weaker material from whipping around.


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## Tozguy (Dec 18, 2015)

Thanks for the prompt replies. All good.
So far I have made a spider for stabilizing long thin stock that sticks out the back of the spindle, a crank hub for turning the spindle by hand, and an insert for centering a drawbar. I had not thought of mounting a work stop but it is an excellent idea. There is some work coming up that requires a work stop so that idea solves the problem for me.
Considering how useful it is to have those threads in the 'forgotten' end of the spindle its odd how little attention it gets.
I'm a bit disappointed that I can't do anything dangerous with it tho.


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## Bill C. (Dec 18, 2015)

If I understand your question there are threads on the back end of your spindle. Some lathes with high speed can whip small diameter material until it bends.  Be there and had it happen before I could stop it.  So some will make stock tubes the thread on to support such material.  Some of the larger spindle bore diameter lathes will have a three jaw chuck mounted on the end to support heavier material.  I hope this helps


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## chips&more (Dec 18, 2015)

Bill C. said:


> If I understand your question there are threads on the back end of your spindle. Some lathes with high speed can whip small diameter material until it bends.  Be there and had it happen before I could stop it.  So some will make stock tubes the thread on to support such material.  Some of the larger spindle bore diameter lathes will have a three jaw chuck mounted on the end to support heavier material.  I hope this helps


Yeah, happened to me too…once. And once is enough! My lathe is about 1,500 lbs and it was hopping on the floor when it happened. Lucky no damage done just had to go change my underwear.


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## Wreck™Wreck (Dec 18, 2015)

A tool manufacturer may do whatever they want as regards design, if they went through the added operations and associated costs of  threading the ID on the back of a lathe spindle there is a very good reason for doing so.


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## chi JBS (Dec 19, 2015)

Bill C. said:


> If I understand your question there are threads on the back end of your spindle. Some lathes with high speed can whip small diameter material until it bends.  Be there and had it happen before I could stop it.  So some will make stock tubes the thread on to support such material.  Some of the larger spindle bore diameter lathes will have a three jaw chuck mounted on the end to support heavier material.  I hope this helps



grin, before I knew what I was doing, I turned a perfectly straight 1/2" dia rod into a perfect  "j".  So it isn't just small dia stuff.


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