# atlas tail stock



## talkingmonkey (Mar 7, 2013)

while using the tail stock on my atlas 12 x 36 lathe today i changed bits and had trouble with the drill spinning.  i would swear there was a recess that held the tang to prevent spinning yesterday. am i losing my mind?


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## iron man (Mar 7, 2013)

Mine did not have one and I got tired of it so with the proper reamer I reamed it out and then I set in and made a way to hold the tang in place. It worked well now I am making a new barrel out of chrome shaft and making it a little longer with some other simple mods I hope to make a better tail stock out of it.. Ray


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## pdentrem (Mar 7, 2013)

There was no tang recess in mine either. The socket has to be clean and in good shape to hold the chuck from turning.
Pierre


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## wa5cab (Mar 7, 2013)

Monkey,

While not being willing to comment on your state of mind, I can confirm that there is no slot in the Atlas tailstock rams to capture the tang on arbors that have one (not all do).

Robert D.


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## talkingmonkey (Mar 7, 2013)

Thank you to everyone who replied.  A mind is a terrible thing to lose.

Jeff :nuts:


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## Ulma Doctor (Mar 7, 2013)

i have an atlas th42 (10x42) 50's vintage, no tang slot in the tail stock here!


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## george wilson (Mar 8, 2013)

No tang in my Hardinge HLVH tailstock either. My 16" Grizzly lathe does have it,though,in the #4 MT tailstock. My first lathe,a 12" Craftsman did not have it.


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## Bubby Sharp in KY (Mar 10, 2013)

talkingmonkey , I put a little chalk on the taper to help hold it . Bubby Sharp in KY


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## DJ Bill (Mar 12, 2013)

Deleted, put post in wrong place.. Apologies.


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## Richard King (Mar 12, 2013)

Hey everyone take a look at this thread and please tell the others about it.  

Thanks.   Rich

http://www.hobby-machinist.com/showthread.php/13710-Method-for-Aligning-the-Tailstock-with-Headstock


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## smirlex (Mar 20, 2013)

talkingmonkey said:


> while using the tail stock on my atlas 12 x 36 lathe today i changed bits and had trouble with the drill spinning.  i would swear there was a recess that held the tang to prevent spinning yesterday. am i losing my mind?


  I was taught that the tang on a MT was there for removal only & not to secure the device. That the taper was all that was required. The taper, male & female had to be clean, free of grease or oil, & no high spots. & if the tang was called upon to prevent the device from tuning it could break it off. I've never seen this happen tho. Thanks
  Hope this keeps me from being deleted.


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## Bill C. (Mar 20, 2013)

talkingmonkey said:


> while using the tail stock on my atlas 12 x 36 lathe today i changed bits and had trouble with the drill spinning. i would swear there was a recess that held the tang to prevent spinning yesterday. am i losing my mind?



The tang is used by other machines like drill presses to keep the holders from spinning.  The tang fits inside a slot built into the spindle and/or adapters of these machines.  Lathes don't used these tangs. Manufacturers used common supply sources.


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## iron man (Mar 20, 2013)

I got tired of the chuck spinning so I re-reamed the taper till it was smooth again then in the key slot I installed a small setscrew no wider than the keyway with a drop of locktite the setscrew stays put and it reaches up and just touches the beginning of the tang closes to the taper I can drill with any drill now and the most that could happen is I could lose a setscrew this has worked for years on my other lathe and I would not change it for anything. more damage is done by spinning than anything else you could do.. Ray


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## timmeh (Jul 10, 2015)

The tang is not there to drive, it is only there for removal. Regardless of what machine it is in. The taper is what is designed to "drive".
"Taper shank drills have morse taper shanks for holding and driving. The tang at the end of the shank is used for ejecting the drill from socket or sleeve."
(Ron Culley's Fitting + Machining)


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## Bill C. (Jul 10, 2015)

Tangs are used in heavy duty drill presses, radial arm models.  I agree lathes as far as I can recall don't.  GE used to give each apprentice a set of sleeves to use with tang drill bits.


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## tertiaryjim (Jul 11, 2015)

One solution is to drill a offset hole in the tailstock quill so a spring-pin inserted in the hole will just clear the tang.
If the drill slips just a bit in the quill it will catch on the pin for an extra bit of hold.
The pin would, of course, have to be recessed in the quill enough to avoid any rubs.
I'm certain, considering the condition of many drill-presses I've seen, that the tang often helps drive the drills.
Have also seen twisted tangs and drills with the tangs gone.
Wish people would learn to clean and dry their holes. Ha!


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## turnitupper (Jul 11, 2015)

tertiaryjim said:


> One solution is to drill a offset hole in the tailstock quill so a spring-pin inserted in the hole will just clear the tang.
> If the drill slips just a bit in the quill it will catch on the pin for an extra bit of hold.
> The pin would, of course, have to be recessed in the quill enough to avoid any rubs.
> I'm certain, considering the condition of many drill-presses I've seen, that the tang often helps drive the drills.
> ...


What would you use? A bidet?.
John.


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## tertiaryjim (Jul 11, 2015)

John
A bidit might be appropriate for some of the yahoos I've worked with.
Gotta go spread some paint on the frames for the wheels to go under my grinder.
Need to be able to role this machine out of the way so I've room to tear something else apart.


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## RJSakowski (Jul 11, 2015)

If the tang was designed for ejecting the taper and not as an anti-rotation device, why would it have two flats?  You could eject it with just a reduced diameter stub on the end.


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## John Hasler (Jul 11, 2015)

RJSakowski said:


> If the tang was designed for ejecting the taper and not as an anti-rotation device, why would it have two flats?  You could eject it with just a reduced diameter stub on the end.


I suspect that when tapers first came into use they could not  be consistently made with sufficient accuracy to work without a tang to prevent rotation.


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## RJSakowski (Jul 11, 2015)

Although Stephen A. Morse invented the Morse taper as a means of driving his newly patented twist drills, there was no attribution of the taper in a patent search under his name.  He did send a master standard to the National Bureau of Standards where is was accepted as a standard.  There have been numerous references to the tang as an anti-rotation device in the literature that I have reviewed , but no reference to a patent. A shame because that would unequivocally answer the question.

A final thought.  Why go to the bother of broaching a socket for the tang if not to prevent rotation?


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## Round in circles (Jul 11, 2015)

RJSakowski said:


> If the tang was designed for ejecting the taper and not as an anti-rotation device, why would it have two flats?  You could eject it with just a reduced diameter stub on the end.



The tang is so that when you use a sleeve  and drive the separating  feather /key in to the sleeve to separate the drill you don't mushroom the softer dead  end of the drill & cause it to jam in the sleeve .
Remember , morse tapers are a system of using friction at /in precision faces to drive the drill  , they are not specific to one model of lathe .
So an 8 mm MT2 could be sleeved up to fit into an MT4 or MT5.

Thinking about it a bit more & still thinking about what I've already said perhaps by only taking the taper so far down and then making the slot for the feather at the end of  it just happens that the tang goes into the slot area as the slot may well be at the end of the length /depth of the taper quite by accident rather than by design . 
I've not found any tangs that fit snugly in the taper at 90 degrees to the feather slot they all stop well before that and you have to rotate the drill to get it to go in any further. 
Could this be because the feather slot has been hot punched in the blank sleeve to make broaching /milling it out easier ?  

I do however had a couple of morse taper drills that  came with the lathe that have been badly ground or turned down on the tang end .
I assumed it was done because of the mushrooming of the tang happening when being brayed out using the wrong face of the feather or an incorrect sort of feather such as one made from ground down tool steel .  or   When someone has walloped the drill in a slipping/ scored /burred /dirty  taper to make it hold and then couldn't easily get it undone again .


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## John Hasler (Jul 11, 2015)

Round in circles said:


> The tang is so that when you use a sleeve  and drive the separating  feather /key in to the sleeve to separate the drill you don't mushroom the softer dead  end of the drill & cause it to jam in the sleeve .


A reduced diameter stub would work as well for that and be easier to make.


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## RJSakowski (Jul 11, 2015)

Round in circles said:


> The tang is so that when you use a sleeve  and drive the separating  feather /key in to the sleeve to separate the drill you don't mushroom the softer dead  end of the drill & cause it to jam in the sleeve .
> Remember , morse tapers are a system of using friction at /in precision faces to drive the drill  , they are not specific to one model of lathe .
> So an 8 mm MT2 could be sleeved up to fit into an MT4 or MT5


Ah, but you don't need a tang with flat sides and corresponding broached socket to be able to drive the the taper out.  A reduced diameter cylindrical sleeve would work as well.  Even if you have the tang as it exists currently, you wouldn't need a broached socket to mate.  A cylindrical; bore will work.  

The hypothesis that I presenting is that the flat sided tang would have been designed with a purpose.  It would cost more to make the taper as designed which would not be good engineering practice unless it was also intended to be an anti-rotation mechanism.

(John, your post came through as I was typing, so please excuse the redundancy)


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## timmeh (Jul 11, 2015)

RJSakowski said:


> The hypothesis that I presenting is that the flat sided tang would have been designed with a purpose.


The tang does have a purpose, that is to assist in removal. It is the taper(self locking) that is designed to provide sufficient friction with which to drive the drill.
If tapers slip it means they are dirty/damaged, and if being driven as they were designed to be, any slippage would result in a sheared tang. Under light load they may slip and catch and appear to have sustained no damage, but i can say from experience that even this can fail. Long story short, if you rely on the tang as an anti rotation device, eventually you will lose a tang.
Grind/turn a tang down, see how long the stub lasts before it mashrooms/bends/breaks.
Make some sleeves as you describe them, let me know how that goes. i.e. trying to separate.
Do a bit of research on levers/wedges first, and have a closer look at a drawing of a morse taper
to see how and why they are made the way they are.
Did my time, broke plenty of drills along the way. Thats life.


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## timmeh (Jul 11, 2015)

Further research through my copy of "Fitting and Machining" (Ron Culley), a text from TAFE studies prior to starting apprenticeship, iv'e found another direct reference.
"Taper shank drills are driven by the taper and not the tang. The tang is designed for ejection not driving.It is essential that the drill shank and socket are a good fit and free of burrs and grit, otherwise slippage will twist the tang."
Not trying to be a wa**er, passing on some information. It is very common, this misconception about taper shank drills.


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## RJSakowski (Jul 12, 2015)

I understand the principle of a locking taper.  I have designed devices with locking tapers in the past.  I have also used Morse tapers for more than forty years.  I also understand the use of a drift to unseat a Morse taper.

My original question was why are there flats on the tang?


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## RJSakowski (Jul 12, 2015)

BTW, Over the years, I have collected a number of straight shank drill bits that have tangs with flats.  Here is an example.
*Besly
Jobbers Length
Tanged
Twist Drills*

High Speed Steel 
Straight Shank

Wire Gage, 
Letter and 
Fractional Sizes
*Catalog Number:  T-105-T*



These surface treated automotive series drills are of the same design and general dimensions as Catl No. T-105 except for the addition of a tang to fit drill holders for the purpose of driving the drill.


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## timmeh (Jul 12, 2015)

Due to the way the sleeve/socket/spindles are made. To reach up the slot to where the drift will be when used for removal. Note that the tang has a considerable amount of clearance in all directions.
Straight shank drills wont fit a morse taper, different kettle of fish altogether.


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## wa5cab (Jul 12, 2015)

RJ (please set up your Signature or sign your posts).

Unless someone turns up an old textbook with a proper bibliography referencing someone's patent, I don't think that you are going to get anything but everyone's opinion.  Of the textbooks that just state a reason without attribution, most seem to go with for removal.

My personal opinion is that it must be for extraction from drill press spindles.  This is based upon experience using taper shank drill bits or arbors with tangs in drill presses.  If the taper comes loose, the tang will continue to drive it but it won't turn true and will drop out noisily as soon as you raise the quill.  So under that circumstance the tang's turning ability makes things worse, not better.


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## tertiaryjim (Jul 12, 2015)

A simple reduced Dia. on the end of the taper with a matching female hole in the bore would have been easyer and cheaper to make.
Yes they would still have to mill a slot in the spindle for removal, on drill presses and such,not tailstocks, but tooling would be easyer to produce.
The tang gives a bit of added holding ability while pressure against the work helps re-seat the taper.
In job shops, there's always those who don't clean the tooling or the bore and the taper cant fully hold due to oil or dirt.
The tang helped prevent tool rotation then and still works now.


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## T Bredehoft (Jul 12, 2015)

This is anecdotal, but I've seen too many sheared tangs to believe they are meant to drive the drill.


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## The Liberal Arts Garage (Jul 12, 2015)

In the course of many years I have seen tapered shank drills turned undersized at
the end- probably shop made........JHBLAG.


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## tertiaryjim (Jul 12, 2015)

Tom
I don't mean to imply the taper shank drive's the bit. That would clearly fail and we all know the taper should hold firmly.
Only mean that the shank can help a little if the bit slips in the fit, at least giving the taper a chance to better grip.


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## Tony Wells (Jul 12, 2015)

If you look at the very end (face) of the tang, you will see that they are not flat, straight across perpendicular to the axis of the tool. This can be a large radius or two angles. This is done to match the angle of the drift key used to remove them. A round stub in the middle could have a bevel, but at the max diameter that would fit where the tang does, it wouldn't function as well as the end of the tang as they are designed.


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## Andre (Jul 12, 2015)

My 13" small spindle south bend, circa 40-50 (guess) does not have a tang holder.

As long as your tapers are clean and for the most part undamaged, you shouldn't have a problem with spinning as long as you are feeding in with the tailstock. Self holding tapers (No drawbar, coller nut, etc) are not very strong without axial clamping force and like to come out.


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## iron man (Jul 15, 2015)

If the tang was just used just to eject it they would or could just be a round pin but instead they made it fit into a nice pocket a lot of work for just an ejection pin. At any rate mine does not spin anymore and ruining the taper all it takes is one spin and the taper is done. It worked so well I made a new barrel with a pocket inside for the tang.. I would not have it any other way now.. do as you will..Ray..

And according to this there are several different drills with a drive tang.

http://www.mfg.mtu.edu/marc/primers/drilling/nomen.html

http://www.amesweb.info/Tooling/TaperShankTwistDrills.aspx


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## Round in circles (Jul 16, 2015)

This thing about the tang on the drill and attachments has puzzled me for a few days as none of the explanations seemed 100% watertight in thought and deed .

Today I picked up a 1 & 1/4 inch morse taper drill, suddenly it dawned on me that most of us  were / are part right and part wrong.

I now strongly feel that the tang is ground on the blank along with the center point hole at both ends  most likely as the first operation in making the drill .
So that the drill/sleeve or mandrel  blank can be held in a device similar to being driven between centres and driven by a dog that the tang locates in/onto so it can be ground between centres on a special multi tooled machine . Once the taper is accurately ground on the drill the mandrel end  can now be accurately /securely held for the flutes to be ground on the drill & for it to be machine sharpened . 

Yes the tang is also ground up for extraction & clearance purposes as well 

The more I looked at the drills , the tang , the centre point in the tang  and the sleeves  etc it became hard to think why none of us had  though of it before .
Can anyone now say otherwise with a greater level of reasoning . ?


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## wa5cab (Jul 17, 2015)

Nope.  Your analysis is quite logical.  You may well have hit the nail on the head.  Although I have seen (and have at least two of) arbors without the tang, I can't ever recall seeing a taper shank drill bit without it.


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## The Liberal Arts Garage (Jul 26, 2015)

More unnecessary advice: why is there a " scar " in your taper socket ? someone
didn't  ( very carefully ) clean the sexy parts before mating.


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## louosten (Aug 21, 2015)

Interesting thread about what the tang is there for...so assuming that it was the original 'driver' for the rotating piece to be made, how do they (the manufacturers) make an MT arbor with no tang, but drawbar threads?

The reason I'm asking this question is that I recently ordered two MT-2 arbors with drawbar threads on Ebay, only to find that the drawbar threads were out of concentricity with the Morse Taper. In other words, if you mount the arbor on the drawbar and rotate it with your fingers (off the machine), the arbor wobbles enough to see in plain sight...almost like the drawbar threads were the last operation and the tap was not plumb.
No harm done other than aggravation, and I got a refund, but it's definitely poor manufacturing repeating itself.

Thanks in advance for comments.


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## Round in circles (Aug 21, 2015)

Machinery has progressed over the years .. 
In days of yore the drawbar  threading  would have been put in place before the taper was made then a live centre or free rotating /live tailstock chuck with a threaded bar in it  be used to support the taper being turned/ground.  
There must be numerous ways of doing it in truth for the above method is just straight out of my imagination .

Doing it on a fair  quality CNC machine nowadays with a capstan head & multi directional capstan work piece holder as part of a the  production event used when making the arbor would be just so easy to get it perfectly right .

Lousten,
  What you said about the draw bar not being central .........  Does it really need to be such a precision alignment  for the draw bar , for the male taper is drawn into the female , so it should fit well no matter if the screw is not true to the central axis .
Your thoughts please.


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## wa5cab (Aug 21, 2015)

The allowable eccentricity of the tapped hole is if nothing else limited by the actual diameter of the hole through the spindle for the draw bar.  The hole will normally be a nominal 3/8".  The tapped hole cannot be eccentric enough that you can't screw the drawbar fully into the arbor without use of a wrench.


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## louosten (Aug 28, 2015)

Gentlemen;

I have sourced some MT-2 arbors with the 3/8" x 16 drawbar threads from Little Machine Shop. When I checked them with my rudimentary method and poor eyesight, they seemed to be properly fabricated and concentric with the rotating drawbar. My gut feel is that the previous items purchased were poorly made, and maybe 1 or 2 steps shy of a full CNC operation.

While I'm still not sure of the actual steps necessary to make the arbors with the drawbar, I' fairly sure that they are initially turned between centers, and the drawbar threads added as a final step. Whether or not it's really important for the threads to be concentric with the piece, I don't know...but when you order an item advertised as a 'precision MT-2 arbor', you certainly don't expect this kind of defect.

Lou O.


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## wa5cab (Aug 28, 2015)

I agree.  The drawbar threads should be concentric with the taper and with the hole for the milling cutter.  Besides the potential difficulty in getting the drawbar to screw into them that I mentioned earlier, it doesn't help the dynamic balance of the machine any to have the drawbar spinning off center.


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