# Making A Live Tailstock Chuck - Why Would You Need One ?



## randyc

A recent thread about re-buiding 18N Jacobs chuck reminded me of a project that I completed a while ago that involved modifying one of these excellent old chucks.  I’m going to reproduce a few of the comments that I made and the original thread can be found here:
http://www.hobby-machinist.com/threads/jacobs-drill-chuck-repair-info.34325/#post-294108

I had recently obtained three Albrecht chucks and already owned a couple of them so the old 18N became redundant although it still had a lot of life left.  I’d recently given a friend a massive ¾ drill chuck that came with some tooling I’d obtained from eBay as a lot buy.

My friend made a very nice live tailstock chuck from it. I was immediately envious and HAD to have one of my own.  So what IS a live tailstock chuck anyway ?

A live chuck is a chuck that is free to rotate while its shank is stationary.  The chuck has an internal shaft that is straight, not tapered, enclosed within a normal Morse tapered body.  The internal shaft is guided within the body by several bearings.

One bearing (or a pair) centers the chuck with the Morse taper body and allows free rotation.  Another bearing is required to accommodate axial thrust as will be shown below in a sketch of the internal details.

The tool, as I made it, is <ahem> somewhat lacking in fine workmanship as can be seen in the following photo:





A live tailstock chuck is useful for several applications, the most common is to grip and support the end of a workpiece while allowing the workpiece to freely rotate.  Of course a center in the tailstock or a steady rest performs the same function, right ?

Yes, and probably a bit better than a live chuck in most cases but there are situations in which the live chuck is a better alternative or even the only alternative.  Taking a light cut on worn commutators of armatures on generators and motors, for example, to expose a new conductive copper surface.

The bearing surfaces at the ends of the armature are usually hardened and centerless ground.  There is no existing center and the hardness usually precludes center drilling and the use of a tailstock center.

One could use a steady rest except that the carriage travel would be severely limited – a live chuck in the tailstock provides considerably more freedom.  This can often makes the difference in a task like the one described above.





If you look carefully at the photo on the left, you’ll note that the carriage is against the base of the steady rest – the carriage cannot get any closer to the end of the shaft.  (Note that a dead center is in the tailstock.  It's not applicable to this post - the center happened to be installed and I simply forgot to remove it.)

On the right, using the live chuck, the carriage is free to move as far as the tailstock base.  The cutting tool can actually reach the front face of the live chuck.  That’s a significant improvement in carriage travel !

This particular 18N chuck had a MT-2 shank, fitting the tailstock of a small Emco 8 x 18 lathe that is partly depicted in the above photos.  Because the MT-2 dimensions are fairly small, there was not much latitude in designing the internal parts.

Ball or roller bearings couldn’t be accommodated without reducing the diameter of the internal shaft of the chuck to a point that it would no longer be rigid enough to support work properly.  I chose to use a long “oilite” sleeve bearing to best support the rotating shaft to keep the shaft diameter as large as possible.

The thrust bearing is simply a hardened 3/8 inch ball.  A live tailstock doesn’t experience much (if any) axial thrust so this simple expedient is more than adequate.  The ball is lubricated with a dab of wheel bearing grease.  The oilite bearing is lubricated with spindle oil.  This is the CAD sketch of the live chuck:





The small #4-40 set screws protrude into a groove on the internal shaft.  In normal operation the screws don’t contact the stationary surface – they are there only to prevent the internal parts from separating.

Perhaps the usage of the live chuck as a work support, as described above would be uncommon.  There is another application for a live chuck that might be frequently useful however.  Some of my work is on a small scale and tapped holes can be as small as #0-80, although that is not common.  Most tapped holes for small work range from #4-40 to #10-32 in my experience.

Smaller tapped holes require some detailed attention to prevent breaking taps.  Perhaps breaking a tap that cost less than $5 U.S. isn’t a major concern but when the tap breaks off in a part that one has expended several hours of work … well, that IS a concern since removing the tap may not be possible.

There are a number of ways to safely tap small holes but most of them require manual methods and can be time-consuming.  The live chuck can allow power tapping with taps as small as #6-32 if the chuck is well-aligned with the spindle axis.  (Smaller taps have been successfully used with this technique but I don’t know if consistent performance is likely.)

I should note that there are many other methods that are useful for power tapping small holes – this is just one of them.





With the lathe turning at slowest spindle RPM and the pilot hole + tap lubed with cutting oil, the tapping process is initiated with the operator lightly gripping the body of the live chuck with his left hand (I used my right hand just for the purposes of this photo).  The loosened tailstock is slowly fed into the work, engaging the tap while gently pushed by the operator’s right hand.





There is no need to be concerned about the depth of the tap because any resistance to the process will be immediately detected by the operator’s left hand.  When the tap bottoms out in the pilot hole (or when flutes are jammed with chips), the live chuck will slip in the operator’s hand and freely rotate, preventing tap breakage.

Note:  this is an appropriate time to suggest that power tapping should be done with spiral taps, not straight-fluted taps.  Chips are cleared more effectively and breakage is minimized using this configuration.

Stopping the lathe and rotating the live chuck CW and CCW slightly to break the chips, the tap can be carefully withdrawn from the work while slowly retracting the tailstock.  To be absolutely safe,you could loosen the live chuck from the tap and withdraw the tailstock, then unthread the tap by hand or with the help of a small tap wrench.

This process can also be used for reaming IF the amount of material to be removed is small – on the order of .001.  This is always contingent on the material and hardness, of course.


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## RJSakowski

randyc said:


> A live chuck is a chuck that is free to rotate while its shank is stationary.  The chuck has an internal shaft that is straight, not tapered, enclosed within a normal Morse tapered body.  The internal shaft is guided within the body by several bearings.


An interesting idea>  How well can you control runout in the chuck?


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## Franko

I have a ball bearing live chuck that I've found pretty useful for several things. It doesn't seem like it would be that useful for threading, since you'd need to crank the tail stock to feed it into a rod. I don't think my tailstock will move unless you turn the handle.

I have a tap holder and a die holder for my tailstock that slide on a rod with a M2 taper that fits my tailstock and freely rotates. You clutch it with your hand and let it slip if it jams or gets too stiff, and it just feeds itself into the work.


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## randyc

RJSakowski said:


> An interesting idea>  How well can you control runout in the chuck?



The use of a live chuck for tapping is not my idea, of course.  I've seen similar (and mostly better) tapping chucks that are both live _and _slide, so that it's not necessary to move the tailstock to feed the tap.  Frankly, I didn't even think of tapping applications when I modified the old 18N, I just wanted a live chuck for those few applications where it might be handy ...

Most of us HSM guys seem to spend a lot - if not most - of our time making tooling to make ..... what ?  That certainly describes me and looking around at the projects that are posted here it describes almost everyone   Certainly nothing wrong with that of course.  I believe that exercising the mind may be even more important than exercising the body once one achieves a certain amount of years.

Controlling the run-out of the chuck is very difficult, there are many variables.  Some dimensional variations can be improved by machining critical dimensions with the device assembled, which is what I did wherever possible.  (I posted a process for truing a drill chuck some time ago.  The same technique was useful for making the live chuck as well.)

But bearing clearance, multiplied by the distance from the chuck to the bearing is a problem with this type of design.  The MT-2 taper dimensions didn't permit the use of precision bearings and the oilite sleeve bearing necessarily must have clearance.

But the live chuck is perfectly workable as is.  When using it for it's intended purpose a couple of times, I dialed in the workpiece by slightly shifting the tailstock offset.

Many would regard this as a major, time-consuming alteration to machine set-up, LOL, but on an old lathe (both of mine are pretty old) it's a common practice since wear along the ways all but assures that the tailstock axis isn't aligned with the spindle axis when moved from one point to another.

Doesn't take any more time than aligning a 4-jaw chuck


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## randyc

Franko said:


> I have a ball bearing live chuck that I've found pretty useful for several things. It doesn't seem like it would be that useful for threading, since you'd need to crank the tail stock to feed it into a rod. I don't think my tailstock will move unless you turn the handle.
> 
> I have a tap holder and a die holder for my tailstock that slide on a rod with a M2 taper that fits my tailstock and freely rotates. You clutch it with your hand and let it slip if it jams or gets too stiff, and it just feeds itself into the work.



I noted that the tool is used on an Emco 8 x 18 lathe.  The small tailstock on that particular machine moves quite easily and the live chuck is _very _useful - at least for me.

The tap/die holder that you describe is precisely what I referred to in my last post.  As I said, they are a better solution for threading.  As I _also _said, that wasn't even in my mind when I made the live chuck


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## Franko

I didn't mean to sound critical, Randy. I was careless reading what you wrote, being mostly dazzled by the pictures. 

I've often thought it would be useful to have a small live 3-jaw chuck for my tailstock for working with tubing that is too big for a live center or my steady rest.


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## f350ca

Good project Randy. I have a live 3 jaw I use to support pipe as Franko said. It would be easy to turn an adaptor that fits inside the tube that can be held in your live chuck.




Greg


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## randyc

Franko said:


> I didn't mean to sound critical, Randy. I was careless reading what you wrote, being mostly dazzled by the pictures.
> 
> I've often thought it would be useful to have a small live 3-jaw chuck for my tailstock for working with tubing that is too big for a live center or my steady rest.



Frank, no sweat, I understood what you meant but it took me a while, LOL.  Using the live chuck for tapping was an afterthought me, not part of my original thought process - your sliding tap holder configuration is better and probably the only practical option for large lathes, where moving the tailstock by hand would be awkward.

Regarding a small live tailstock 3-jaw, take a look at darkzero's post #18 in this thread - very nice set-up:

http://www.hobby-machinist.com/threads/jacobs-drill-chuck-repair-info.34325/#post-294789


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## Franko

Yeah, I like darkzero's live chuck. I will probably rig something up like that. Most of my effort is directed toward making a stand for my soon to be here PM1127, and I've been doing some mill upgrades.

I mentioned in another thread that I discovered the bolts holding the column to the base were very loose, finger loose. I have no idea how long they've been that way or how it happened. The last few weeks I've been tuning it up, adjusting the ways, installing a power feed, DROs, and checking for square. This was after I discovered the ways on my lathe were too loose causing me to break an insert a month ago.

I have a suitable chuck that I got to attach to a small rotary table. The trick will be coming up with a spinning backplate. I can't see where the bearing is on my live drill chuck with a m2 taper. If it will come out and is a jacobs or threaded, I might be able to make a backplate to switch them around.


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## Franko

I have tapped with my lathe using the regular tailstock drill chuck, turning it by hand and feeding it with the tailstock handwheel.


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## chips&more

Very nice…I was lucky enough to find an armature turner and I harvested the chuck off of it. I fitted the chuck with a #3 Morse and made new fingers for it, works great. Can’t say that I have used it much for turning commutators. But, I sure have used it when a long project did not have a center hole. With this technique there really is no worry about run-out. And for tapping, I usually just chuck the gun tap into the chuck. But, I do have one of those sliding spinning things. On really small taps I will just start it with a couple of threads and then finish the job over in the bench vise. And I do have a spinning tail stock chuck somewhere? I got it about 20 years ago from Enco. Thought I needed it and I just might one of these days, if I can find it…Good Luck, Dave.


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## randyc

chips&more said:


> Very nice…I was lucky enough to find an armature turner and I harvested the chuck off of it. I fitted the chuck with a #3 Morse and made new fingers for it, works great. Can’t say that I have used it much for turning commutators. But, I sure have used it when a long project did not have a center hole. With this technique there really is no worry about run-out. And for tapping, I usually just chuck the gun tap into the chuck. But, I do have one of those sliding spinning things. On really small taps I will just start it with a couple of threads and then finish the job over in the bench vise. And I do have a spinning tail stock chuck somewhere? I got it about 20 years ago from Enco. Thought I needed it and I just might one of these days, if I can find it…Good Luck, Dave.



I like both of those tools !  The little blue one would work great for taps smaller than #4-40


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## benmychree

randyc said:


> A recent thread about re-buiding 18N Jacobs chuck reminded me of a project that I completed a while ago that involved modifying one of these excellent old chucks.  I’m going to reproduce a few of the comments that I made and the original thread can be found here:
> http://www.hobby-machinist.com/threads/jacobs-drill-chuck-repair-info.34325/#post-294108
> 
> I had recently obtained three Albrecht chucks and already owned a couple of them so the old 18N became redundant although it still had a lot of life left.  I’d recently given a friend a massive ¾ drill chuck that came with some tooling I’d obtained from eBay as a lot buy.
> 
> My friend made a very nice live tailstock chuck from it. I was immediately envious and HAD to have one of my own.  So what IS a live tailstock chuck anyway ?
> 
> A live chuck is a chuck that is free to rotate while its shank is stationary.  The chuck has an internal shaft that is straight, not tapered, enclosed within a normal Morse tapered body.  The internal shaft is guided within the body by several bearings.
> 
> One bearing (or a pair) centers the chuck with the Morse taper body and allows free rotation.  Another bearing is required to accommodate axial thrust as will be shown below in a sketch of the internal details.
> 
> The tool, as I made it, is <ahem> somewhat lacking in fine workmanship as can be seen in the following photo:
> 
> 
> 
> 
> 
> A live tailstock chuck is useful for several applications, the most common is to grip and support the end of a workpiece while allowing the workpiece to freely rotate.  Of course a center in the tailstock or a steady rest performs the same function, right ?
> 
> Yes, and probably a bit better than a live chuck in most cases but there are situations in which the live chuck is a better alternative or even the only alternative.  Taking a light cut on worn commutators of armatures on generators and motors, for example, to expose a new conductive copper surface.
> 
> The bearing surfaces at the ends of the armature are usually hardened and centerless ground.  There is no existing center and the hardness usually precludes center drilling and the use of a tailstock center.
> 
> One could use a steady rest except that the carriage travel would be severely limited – a live chuck in the tailstock provides considerably more freedom.  This can often makes the difference in a task like the one described above.
> 
> 
> 
> 
> 
> If you look carefully at the photo on the left, you’ll note that the carriage is against the base of the steady rest – the carriage cannot get any closer to the end of the shaft.  (Note that a dead center is in the tailstock.  It's not applicable to this post - the center happened to be installed and I simply forgot to remove it.)
> 
> On the right, using the live chuck, the carriage is free to move as far as the tailstock base.  The cutting tool can actually reach the front face of the live chuck.  That’s a significant improvement in carriage travel !
> 
> This particular 18N chuck had a MT-2 shank, fitting the tailstock of a small Emco 8 x 18 lathe that is partly depicted in the above photos.  Because the MT-2 dimensions are fairly small, there was not much latitude in designing the internal parts.
> 
> Ball or roller bearings couldn’t be accommodated without reducing the diameter of the internal shaft of the chuck to a point that it would no longer be rigid enough to support work properly.  I chose to use a long “oilite” sleeve bearing to best support the rotating shaft to keep the shaft diameter as large as possible.
> 
> The thrust bearing is simply a hardened 3/8 inch ball.  A live tailstock doesn’t experience much (if any) axial thrust so this simple expedient is more than adequate.  The ball is lubricated with a dab of wheel bearing grease.  The oilite bearing is lubricated with spindle oil.  This is the CAD sketch of the live chuck:
> 
> 
> 
> 
> 
> The small #4-40 set screws protrude into a groove on the internal shaft.  In normal operation the screws don’t contact the stationary surface – they are there only to prevent the internal parts from separating.
> 
> Perhaps the usage of the live chuck as a work support, as described above would be uncommon.  There is another application for a live chuck that might be frequently useful however.  Some of my work is on a small scale and tapped holes can be as small as #0-80, although that is not common.  Most tapped holes for small work range from #4-40 to #10-32 in my experience.
> 
> Smaller tapped holes require some detailed attention to prevent breaking taps.  Perhaps breaking a tap that cost less than $5 U.S. isn’t a major concern but when the tap breaks off in a part that one has expended several hours of work … well, that IS a concern since removing the tap may not be possible.
> 
> There are a number of ways to safely tap small holes but most of them require manual methods and can be time-consuming.  The live chuck can allow power tapping with taps as small as #6-32 if the chuck is well-aligned with the spindle axis.  (Smaller taps have been successfully used with this technique but I don’t know if consistent performance is likely.)
> 
> I should note that there are many other methods that are useful for power tapping small holes – this is just one of them.
> 
> 
> 
> 
> 
> With the lathe turning at slowest spindle RPM and the pilot hole + tap lubed with cutting oil, the tapping process is initiated with the operator lightly gripping the body of the live chuck with his left hand (I used my right hand just for the purposes of this photo).  The loosened tailstock is slowly fed into the work, engaging the tap while gently pushed by the operator’s right hand.
> 
> 
> 
> 
> 
> There is no need to be concerned about the depth of the tap because any resistance to the process will be immediately detected by the operator’s left hand.  When the tap bottoms out in the pilot hole (or when flutes are jammed with chips), the live chuck will slip in the operator’s hand and freely rotate, preventing tap breakage.
> 
> Note:  this is an appropriate time to suggest that power tapping should be done with spiral taps, not straight-fluted taps.  Chips are cleared more effectively and breakage is minimized using this configuration.
> 
> Stopping the lathe and rotating the live chuck CW and CCW slightly to break the chips, the tap can be carefully withdrawn from the work while slowly retracting the tailstock.  To be absolutely safe,you could loosen the live chuck from the tap and withdraw the tailstock, then unthread the tap by hand or with the help of a small tap wrench.
> 
> This process can also be used for reaming IF the amount of material to be removed is small – on the order of .001.  This is always contingent on the material and hardness, of course.


Jacobs made a chuck especially for armatures, but not to this plan, which I suspect would have problems with runout; they made their chuck with bronze jaws to bear on the armature shaft, this is immune from the runout issue.


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## randyc

benmychree said:


> Jacobs made a chuck especially for armatures, but not to this plan, which I suspect would have problems with runout; they made their chuck with bronze jaws to bear on the armature shaft, this is immune from the runout issue.



Yes, I've owned one of those for an old Atlas and Dave attached a photo in post #11 above.  The design is not immune from runout, however, since it is exactly the same as their drill chuck design and the drill chucks are _definitely_ susceptible to runout.

The biggest problem with bronze jaws is that they ARE the bearing contact and therefore must always run on smooth surfaces.  A live chuck like the one I described can be used on _any_ surface, rough or smooth because it's bearings are self-contained.


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## BillWood

Hello,

Nice idea, am puzzled about how you manage to seat the ballbearing inside the bottom of the morse taper.

See attached picture for question.

I could make the recess in the end of the straight shaft but not at the bottom of the internal morse taper.

Bill


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## randyc

BillWood said:


> Hello,
> 
> Nice idea, am puzzled about how you manage to seat the ballbearing inside the bottom of the morse taper.
> 
> See attached picture for question.
> 
> I could make the recess in the end of the straight shaft but not at the bottom of the internal morse taper.
> 
> Bill



I used a ball end mill in the lathe tailstock.  Gotta' run the lathe REAL slow or the end mill will chatter like crazy !





There should be very little thrust on the ball so countersunk holes would work just as well IF one has a l-o-n-g center drill or countersink.  You can eliminate that problem completely by making a separate disc with the ball socket machined in it; just drop it down the reamed hole - it's not going anywhere   In fact, as I think about it, that would be better than the original design because the disc would self-align with the ball -


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## randyc

I posted a thread some time back about tailstock tooling and I just recalled one of the suggestions in that thread that relates to live tailstock chucks.  This is an expediency and only useful for smaller diameter work.  In the photo below, an oilite bearing is held in a drill chuck.  The bore of the bearing is selected to accommodate the work, which rides within and is supported by the bearing.





There are several obvious limitations, the first being the size of the drill chuck.  The work must also be small enough and of an appropriate diameter to fit the bore of the bearing (although it is certainly possible to modify the bore to fit the work piece diameter).  The workpiece, at least that portion that is supported by the oilite bearing, must have a very smooth surface.


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## BillWood

Does this mean that an el cheapo  live centre could be made by turning the end of the workpiece down to an appropriate diameter and running any type of bearing in a tailstock mounted Jacobs chuck ?


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## randyc

BillWood said:


> Does this mean that an el cheapo  live centre could be made by turning the end of the workpiece down to an appropriate diameter and running any type of bearing in a tailstock mounted Jacobs chuck ?



Yes, you're exactly right.  One limitation, of course, is the concentricity/alignment of the drill chuck with the spindle axis.  It would be a good idea to check this and, if required, rotate the chuck in the tailstock to a couple of different positions until the best one is found.


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