releasing tapers

[John Brown 18Participant @johnbrown18]

A complete beginner, I have purchased a Warco WM250 lathe. I am nervous about inserting the tapers in the tailstock (MT2) and headstock MT3 in case I can't get them out again. The tailstock taper is supposed to be self releasing which, I guess, means that if I wind the arbor right in it will pop out. Can you confirm this? Is it OK to release the headstock taper by threading a drift into the open end of the headstock and whacking it with a rubber hammer? I have bought a drill chuck for the tailstock but it is visibly shorter than the supplied MT2 centre. It is threaded M10. Could I simple lengthen it with threaded rod to reach a length suitable for the self eject to work?

[John Brown 18Participant @johnbrown18]

[Chris TriceParticipant @christrice43267]

The answer is yes to all your questions. As you've surmised, you need to make sure the small end of the taper has a tang or piece of studding making it long enough to self eject.

[Nick WheelerParticipant @nickwheeler]

The tailstock ought to release when the scale on it is at zero. I must investigate why my WM250 has stopped doing this. If you can get to the back of the taper, when using one in a spindle, then a light tap with a decent hammer is by far the easiest and best way of releasing it. Just like releasing the balljoints on car suspensions

[Michael GilliganParticipant @michaelgilligan61133]

Posted by John Brown 18 on 10/02/2019 21:54:00:

… Is it OK to release the headstock taper by threading a drift into the open end of the headstock and whacking it with a rubber hammer?

.

Yes, as Chris said, it's O.K.

But my personal preference is a copper hammer, which gives a shorter & sharper shock.

MichaelG.

[Mike PooleParticipant @mikepoole82104]

A taper with a thread in the small end is for use with a drawbar which is not really needed for drilling, Arceurotrade have screw in tangs to facilitate using a taper like this in self ejecting tailstocks and the use of a tapered drift in typical drilling machine spindles. If you do not need a drawbar type taper it can probably be changed for a tang type morse taper.

Mike

[SillyOldDufferModerator @sillyoldduffer]

Hi John,

Q. The tailstock taper is supposed to be self releasing which, I guess, means that if I wind the arbor right in it will pop out. Can you confirm this?

A. Yes. But not if the taper is too short to reach the rod inside that pushes it out. (They sometimes are.) You can find out without risk of jamming the taper by winding the tailstock fully in (ie reading 0 or less than zero on the plunger scale). Then gently feed the taper in. If it won't go in far enough to wedge you are OK. If it does wedge, you need to either:

1. Replace the taper with a longer one. (They're not very dear), or
2. Cut a short length of loose rod and pop it inside the female so the taper is pushed out by it, or
3. You have the type that can be extended with a short bit of M10 studding and that's what I'd do. Test for length as above.

A stuck taper can generally be released fairly easily by pulling or tapping it out or with a home made wedge. More a nuisance than a crisis unless the taper has been hammered in (don't) or has corroded in place. Tapers are usually made of hardened steel and are difficult to modify: if you want to shorten one use a grinder.

Q. Is it OK to release the headstock taper by threading a drift into the open end of the headstock and whacking it with a rubber hammer? A. yes, but make sure it doesn't fly out and dent the bed. Put a bit of plank on the ways to protect them, also when swapping chucks – in case you drop one!

Have fun,

Dave

PS Owned a lathe for a few years now and have yet to use the headstock taper for anything.  Most work is held with chucks.

PPS.  Everyone else types faster than me…

 

Edited By SillyOldDuffer on 10/02/2019 22:27:25

[not done it yetParticipant @notdoneityet]

Wedges are probably preferable to thumping, but a soft metal hammer is OK to use – but not use a steel headed one!

The headstock taper is mostly only used for turning between centres (work can be removed and replaced without fear of concentricity problems). If milling with the lathe a tool holder would need a drawbar, just like a mill.

Tangs on Morse tapers were there, I believe, mainly for ease of removal with a wedge (through the quill), but also helped prevent the taper turning and screwing up the machine if it jammed up or was not insered tightly enough before starting work.

[BazyleParticipant @bazyle]

Sometimes you get second hand tapers that have been shortened because someone whinged that it was ejecting before the tailstock got to zero when screwed back. Then in another lathe it is too short If you don't get round to a permanent lengthening have a ball bearing rather than a bit of rod to put in the tailstock ahead of the taper (Above SOD post item 2) When the taper is withdrawn later on the bearing just rolls out. (and disappears under the bench so have more than one)

[Chris TriceParticipant @christrice43267]

Posted by not done it yet on 10/02/2019 22:50:44:

Tangs on Morse tapers were there, I believe, mainly for ease of removal with a wedge (through the quill), but also helped prevent the taper turning and screwing up the machine if it jammed up or was not insered tightly enough before starting work.

Pretty certain tangs were never intended for anti rotation duties in respect of resisting machining forces in the same way that the slot on the side some collets is only there to resist rotation while being done up. The actual cutting force is taken (or should be) by the taper surface I believe but happy to be proven wrong. If the tang or slot is taking the load, the collet or taper is not fitted sufficiently firmly.

[HopperParticipant @hopper]

Yep. Tang is not designed to transmit load, ie stop rotation. I've seen more than one tang twisted off on large drill bits over the years where the taper was not doing the driving due to swarf, damage etc. The tang is put there for ejection purposes.

[not done it yetParticipant @notdoneityet]

Posted by Chris Trice on 11/02/2019 00:56:15:

Posted by not done it yet on 10/02/2019 22:50:44:

Tangs on Morse tapers were there, I believe, mainly for ease of removal with a wedge (through the quill), but also helped prevent the taper turning and screwing up the machine if it jammed up or was not insered tightly enough before starting work.

Pretty certain tangs were never intended for anti rotation duties in respect of resisting machining forces in the same way that the slot on the side some collets is only there to resist rotation while being done up. The actual cutting force is taken (or should be) by the taper surface I believe but happy to be proven wrong. If the tang or slot is taking the load, the collet or taper is not fitted sufficiently firmly.

Chris,

l entirely agree with you. But I have seen a few tangs that have been severely twisted, which would have really screwed up the morse taper surfaces had the tang not been there and the drill had continued to run! Tanged drills clearly were all of the same length Morse taper, not like the modern day tool-holding fittings. They also only fitted in a fixed position – so the wedge went in over the tang….

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, both Chris and Hopper are correct, the tang is for ejection purpose only. see page 19 of this **LINK**. The driving force on a taper drill should only be transmitted by the friction between the drill taper and the machine socket, therefore these should always be kept in good condition. Many times in industry, the unworthy have used the closest taper drill they could lay their hands on, to use as a hammer on the drift to knock out the drill that is still in the machine, which puts small dents in the taper and stops them from fitting correctly, thus when used next time often twists the tang and with heavy cuts, will rip it off completely.

Regards Nick.

[JasonBModerator @jasonb]

Using a screw in tang on your tailstock arbor will cost you about 20-25mm of tailstock travel. Easier to saw off a bit of studding or end of a bolt to suit the thread, saw a screwdriver slot across one end and then just screw that into the arbors end.

[Nicholas FarrParticipant @nicholasfarr14254]

Posted by not done it yet on 11/02/2019 07:23:17:

Posted by Chris Trice on 11/02/2019 00:56:15:

Posted by not done it yet on 10/02/2019 22:50:44:

Tangs on Morse tapers were there, I believe, mainly for ease of removal with a wedge (through the quill), but also helped prevent the taper turning and screwing up the machine if it jammed up or was not insered tightly enough before starting work.

Pretty certain tangs were never intended for anti rotation duties in respect of resisting machining forces in the same way that the slot on the side some collets is only there to resist rotation while being done up. The actual cutting force is taken (or should be) by the taper surface I believe but happy to be proven wrong. If the tang or slot is taking the load, the collet or taper is not fitted sufficiently firmly.

Chris,

l entirely agree with you. But I have seen a few tangs that have been severely twisted, which would have really screwed up the morse taper surfaces had the tang not been there and the drill had continued to run! Tanged drills clearly were all of the same length Morse taper, not like the modern day tool-holding fittings. They also only fitted in a fixed position – so the wedge went in over the tang….

Hi NDIY, if this happens, then this usually means that the socket in the machine is badly worn or damaged already, or the taper on the drill is badly worn or damaged. If it is the drill, then it is not worthy of use, if it's the machine socket then steps should be taken to correct it.

Regards Nick.

Edited By Nicholas Farr on 11/02/2019 07:55:52

[Nicholas FarrParticipant @nicholasfarr14254]

Posted by JasonB on 11/02/2019 07:37:26:

Using a screw in tang on your tailstock arbor will cost you about 20-25mm of tailstock travel. Easier to saw off a bit of studding or end of a bolt to suit the thread, saw a screwdriver slot across one end and then just screw that into the arbors end.

Hi, I have one that I just use a grub screw in when needed.

Regards Nick.

[not done it yetParticipant @notdoneityet]

Look guys, I know the drive should be friction between the tapers, but answer me this: Why was a tang fitted, when a dome (or even flat surface) would have sufficed as a point of action for the wedge? Why was the drill only able to be inserted in that orientaion.

In other words, was the tang a poor design or was it there as a back up tell-tale sign (that all was not well) before the taper surfaces were totally screwed up?

I’m not a mechanical engineer, so please give me a good design reason why the tang was developed in that shape, ‘cos those guys that designed it had a good reason for that shape. If it would have been better just flat topped, that is how they would have done it – simpler and faster not to have to locate the tang in the spindle slot, for instance.

[John Brown 18Participant @johnbrown18]

Many thanks to all of you who have replied. Much appreciated and will certainly allow me to proceed. Daresay I will be back with more.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by not done it yet on 11/02/2019 08:26:08:

Look guys, I know the drive should be friction between the tapers, but answer me this: Why was a tang fitted …

.

The definitive source of information would be the original patent … but I have yet to locate a copy.

What I have learned, however, is that the taper drive with tang was patented by Samuel Colt, before Stephen Morse patented his drill.

Ref: **LINK**

https://books.google.co.uk/books?id=mkoSDQAAQBAJ&pg=PT130&lpg=PT130&dq=morse+taper+shank+patent&source=bl&ots=oJYnUYVVTC&sig=ACfU3U1OYvbO47dqoJ1JUE_dl7bZF5XpIg&hl=en&sa=X&ved=2ahUKEwiitPDvrbPgAhWt6uAKHa2ADZsQ6AEwGXoECAkQAQ#v=onepage&q=morse%20taper%20shank%20patent&f=false

MichaelG.

[HopperParticipant @hopper]

NDIY raises a good point indeed. Why a tang captive in a slot and unable to rotate if purpose, as has traditionally been claimed, is merely ejection? A round hump would indeed do the same job for ejection purposes.

Is it like the woodruff key used on a tapered shaft where it fits in a tapered hole, as commonly used on motorbike engine sprockets etc? The drive, supposedly, is all by the taper. But the key, as traditionally claimed, is there just in case the taper lets go momentarily. It supposedly holds the pieces in place so the taper can pick up its grip again.

In this case, I don't think the woodruff key alone would transmit the full power of a, say, 80hp engine if the shaft were a parallel sliding fit in the sprocket so all load was on the key. But its enough to hold the tapered pieces in line if they begin to partially lose their grip.

So maybe the tang acts the same way? It won't transmit the full power as evidenced by drills with snapped off tangs. But it could be just enough to catch a slightly shifting taper before it fully lets loose, and allow it to regain its grip?

Can't find any specific reference in Machinery's Handbook or others either way. Would be interesting to learn where the traditional wisdom originated.

 

Edited By Hopper on 11/02/2019 10:48:17

[Chris TriceParticipant @christrice43267]

I have a recollection that it's something to do with stopping the drill rotating when being advanced or held by a tailstock centre (same as a reamer). Most taper shank drills have centres drilled in them. The rounded end is merely to avoid a corner being burred over if removed by a drift. I've no idea why some lathe tailstocks only allow a drill to fit in a particular position.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Hopper on 11/02/2019 10:43:05:

NDIY raises a good point indeed. Why a tang captive in a slot and unable to rotate if purpose, as has traditionally been claimed, is merely ejection? A round hump would indeed do the same job for ejection purposes.

[ … ]

Can't find any specific reference in Machinery's Handbook or others either way. Would be interesting to learn where the traditional wisdom originated.

.

The best I can find in Machinery's is under 'Twist Drills'

Tang: The flattened end of a taper shank, intended to fit into a driving slot in the socket.

Tang Drive: Two opposite parallel driving flats on the end of a straight shank.

.

I'm sure NDIY can take that as some endorsement

MichaelG.

[egaParticipant @ega]

Posted by Nicholas Farr on 11/02/2019 07:27:50:

Hi, both Chris and Hopper are correct, the tang is for ejection purpose only. see page 19 of this **LINK**. The driving force on a taper drill should only be transmitted by the friction between the drill taper and the machine socket, therefore these should always be kept in good condition. Many times in industry, the unworthy have used the closest taper drill they could lay their hands on, to use as a hammer on the drift to knock out the drill that is still in the machine, which puts small dents in the taper and stops them from fitting correctly, thus when used next time often twists the tang and with heavy cuts, will rip it off completely.

Regards Nick.

Paragraph 4 on your linked page also makes the case for a draw bar – not, of course, possible with a normal MT shank drill. Interesting point, too, about the size of pilot holes.

I once saw a suggestion on an American site for the incorporation of an off centre cross pin in the lathe barrel positioned so as to engage with the tang.

As to the shape of the tang, this has to be such as to allow the taper drift inserted from the side through the slot in the quill to engage with it.

[Peter G. ShawParticipant @peterg-shaw75338]

My lathe, a Warco 220/Mashstroy C210T has a self-ejecting MT2 tailstock. Originally I used a drill chuck with a MT1 taper on the end which I fitted into a MT1-MT2 adaptor. In this mode it worked satisfactorily, but suffered from a large tailstock travel loss. Eventually I replaced the MT1 taper with the correct adaptor for the chuck and gained some, but not all of the missing travel. I then removed the tang, rounded the end, and found that I had removed too much! Ok mea culpa, but tool removal became difficult so I had to add a bit of metal back on to the end of the MT2 taper – a thick washer araldited in place.

Same thing happed with my running centre. (You would think I had learned from the drill chuck attempt, but actually I did them both at the same time.)

So, the point I am making is that in my case, there is a sweet spot for tang reduction to enable full travel of the tailstock, along with correct self-ejection. I think it may have been the late John Stevenson who, correctly I believe, said that this looks like poor tailstock design. However, bodging like this is possibly the best way forward for my lathe.

In respect of using them on other lathes etc, it will not happen here – I only have the one lathe. What happens when I have finished with this lathe is very unlikely to concern me – the lathe itself is not the best in the world and will only go for a low price. In anycase, if it is sold, it will probably be sold as a job lot, ie lathe & accessories. In any case, the adaptors are reasonably cheap and can be easily replaced if necessary.

Peter G. Shaw

[SillyOldDufferModerator @sillyoldduffer]

Posted by Michael Gilligan on 11/02/2019 11:04:51:

Posted by Hopper on 11/02/2019 10:43:05:

NDIY raises a good point indeed. Why a tang captive in a slot and unable to rotate if purpose, as has traditionally been claimed, is merely ejection? A round hump would indeed do the same job for ejection purposes.

[ … ]

Can't find any specific reference in Machinery's Handbook or others either way. Would be interesting to learn where the traditional wisdom originated.

.

The best I can find in Machinery's is under 'Twist Drills'

Tang: The flattened end of a taper shank, intended to fit into a driving slot in the socket.

Tang Drive: Two opposite parallel driving flats on the end of a straight shank.

.

I'm sure NDIY can take that as some endorsement

MichaelG.

Tapers are puzzling in other ways too – like the strange choice of angles! The reason some shanks are fitted with a tang may be lost in the mists of time, so here's my theory.

The quality of a taper's grip depends on the male and female being well matched in every respect. It's important for both to have a good finish. Carelessness, dirt, wear and dings all reduce the effectiveness of the joint, and it's not unknown for them to slip.

Allowing a taper shank to spin in its socket damages both rather badly. Galling, tears, scratches and loss of circularity. Once damaged, slipping and even more damage becomes ever more likely. Although shanks are cheap and easily replaced, the socket is part of the machine and fixing it less straightforward. In a world where machines not busy cutting metal are nothing but a waste of money it pays to protect the machine from outages due to accidental damage.

My guess is the tang is only there to stop an accidentally loose taper spinning in the socket and damaging the machine. Tangs might be less popular today, at least on automatics. I suspect many modern machines can detect when a tool isn't cutting properly and reject it automatically, or stop and alert the operator. Perhaps a CNC expert will tell me I'm dreaming again?

Dave

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