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releasing tapers

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John Brown 1810/02/2019 21:54:00
3 forum posts

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?

Chris Trice10/02/2019 22:03:27
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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.

Nicholas Wheeler 110/02/2019 22:10:55
257 forum posts
13 photos

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 Gilligan10/02/2019 22:11:51
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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 Poole10/02/2019 22:20:34
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2012 forum posts
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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

SillyOldDuffer10/02/2019 22:23:12
4521 forum posts
971 photos

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 yet10/02/2019 22:50:44
3145 forum posts
11 photos

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.

Bazyle11/02/2019 00:25:12
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4647 forum posts
185 photos

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 Trice11/02/2019 00:56:15
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1362 forum posts
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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.

Hopper11/02/2019 07:10:18
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3651 forum posts
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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 yet11/02/2019 07:23:17
3145 forum posts
11 photos
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 Farr11/02/2019 07:27:50
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1902 forum posts
920 photos

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.

JasonB11/02/2019 07:37:26
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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 Farr11/02/2019 07:40:17
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1902 forum posts
920 photos
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 Farr11/02/2019 07:52:57
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1902 forum posts
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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 yet11/02/2019 08:26:08
3145 forum posts
11 photos

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 1811/02/2019 10:05:08
3 forum posts

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 Gilligan11/02/2019 10:20:48
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13547 forum posts
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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.

Hopper11/02/2019 10:43:05
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3651 forum posts
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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 Trice11/02/2019 10:52:20
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1362 forum posts
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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.

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