“Tang” on the end of a male Morse taper?

[Andrew TinsleyParticipant @andrewtinsley63637]

I assume that "tang" is the correct description for the flats on the end of male Morse tapers?

I have always assumed that they were some locating device to ensure that the taper entered its socket in a defined orientation. But thinking about it, I have never seen the equivalent slot for the tang on a female Morse taper.

I ask because I have a multi position capstan turret that pushes into the tailstock Morse taper. With this device. It is essential that the MT goes into the tailstock in a precise position, for obvious reasons!

My tailstock MT is plain, so how is the best way to ensure the correct orientation for the capstan turret?

Andrew.

[Andrew TinsleyParticipant @andrewtinsley63637]

[Nick HulmeParticipant @nickhulme30114]

Posted by Andrew Tinsley on 06/01/2017 21:50:35:

I assume that "tang" is the correct description for the flats on the end of male Morse tapers?

I have always assumed that they were some locating device to ensure that the taper entered its socket in a defined orientation.

I think it was there specifically for machines with no auto-eject, no draw bar and a cross-slot in the quill where a taper wedge is driven in to release the tool,

– Nick

[Ian PParticipant @ianp]

There are many MT sockets that have the female feature, the main purpose of which is to eliminate the possibility of the taper surfaces getting scored under heavy load. The tailstock on my lathe is so equipped.

Its not obvious to me why the position of the capstan male taper is at all critical as the selected tool shoudl be exactly on the same axis.

Ian P

[MWParticipant @mw27036]

Posted by Nick Hulme on 06/01/2017 22:02:27:

Posted by Andrew Tinsley on 06/01/2017 21:50:35:

I assume that "tang" is the correct description for the flats on the end of male Morse tapers?

I have always assumed that they were some locating device to ensure that the taper entered its socket in a defined orientation.

I think it was there specifically for machines with no auto-eject, no draw bar and a cross-slot in the quill where a taper wedge is driven in to release the tool,

– Nick

Yep, that's right, it's named a drill drift, one of the first things I made.

Michael W

[Michael GilliganParticipant @michaelgilligan61133]

Andrew,

Here is a picture clearly showing the extraction slot, as mentioned by Nick.

**LINK**

https://goo.gl/images/RD4VhE

… nothing special; just the first one I found.

MichaelG.

[EmgeeParticipant @emgee]

Andrew, fit a 25mm long false tool in the turret and grip lightly in the 3j sc chuck or collet, with the turret release knob in the operating position move the tailstock onto the MT shank to seat the MT into the tailstock, release from the chuck and set the turret finally with a copper or lead hammer. This will ensure concentricity of the turret in your chosen position. Most turrets are built on a MT shank with tang which aligns the tool as built.

Emgee

[VicParticipant @vic]

My milling machine also has some kind of slot in the quill to take the tang.

[not done it yetParticipant @notdoneityet]

The only tools with a tang are axial thrust types, so the morse taper tightens (if anything) as the pressure is applied. The tang is not there to impart any drive, but only to effect ejection with the aid of a wedge.

Drawbars are required for non-axial thrust duties, such as side milling, to avoid the tool loosening in the holder.

Drawbar versions can be converted by screwing in a tang, while many threaded male tapers need a bolt, or similar, fitted to enable them to eject from a tailstock, per eg.

Your morse taper is both your alignment and grip for the tool, so it is of the utmost importance to keep both male and female surfaces scrupulously clean.

[John ReeseParticipant @johnreese12848]

NDIY has the best description of the purpose of the tang I have seen. Thanks.

[Roger Provins 2Participant @rogerprovins2]

Posted by not done it yet on 06/01/2017 23:39:30:……, while many threaded male tapers need a bolt, or similar, fitted to enable them to eject from a tailstock, per eg.

I've often found this necessary but wondered if what I was doing was correct. Glad to now know it is the right method.

Roger

[Mike PooleParticipant @mikepoole82104]

Posted by Ian Phillips on 06/01/2017 22:05:45:

Its not obvious to me why the position of the capstan male taper is at all critical as the selected tool shoudl be exactly on the same axis.

Ian P

I agree with Ian, the tools mounted on the turret should be on the lathe axis and the position of the morse taper will not change this, if the tools do not align with the lathe axis then there is a problem with the turret indexing register and rotating the morse taper will not change this, it will only move the error around the axis.

Mike

[Andrew TinsleyParticipant @andrewtinsley63637]

Thanks gentlemen,

Emgee, that is exactly what I would do to align a tool position of the turret, to the axis of the lathe. Those of you who doubt that any alignment is required, please think again! The turret rotates between indented positions. So if one tool happens to be on lathe centres (highly unlikely) then rotating the turret around the MT will most certainly put it off alignment. Simply by inserting the turret into the MT and rotating the turret about the axis of the MT will show this to be true.

I have probably made a poor description of the turret and hence the incorrect answers! I should have realised that the tang was for ejection purposes only, in conjunction with a slot in the female taper. Heavens knows that I have done this enough times! The brain seems to fade when confronted with simple model engineering problems. Very odd as I am up to speed on my other (practical) hobbies. I suspect that I get overawed by things machine tool!

Thanks again,

Andrew.

Edited By Andrew Tinsley on 07/01/2017 10:45:56

[Anonymous]

Posted by Andrew Tinsley on 07/01/2017 10:44:20:

Those of you who doubt that any alignment is required, please think again!

Really? It must be a very oddly designed capstan unit if by twisting it the selected tool moves off the axis of the lathe.

A properly designed tailstock capstan unit will have the axis of the indexed tool hole coincident with the axis of morse taper shank that goes into the tailstock. That being the case rotating the whole capstan unit doesn't change the alignment of the tool relative to the lathe axis. Always assuming of course that the tailstock is properly aligned with the lathe axis in the first place.

I don't have a tailstock mounted capstan on my manual lathe (I've got a proper bed mounted one) but I do have a tailstock capstan on the repetition lathe:

It doesn't need aligning.

It would be interesting to see a picture of your capstan unit, to see if it really does need alignment.

Andrew

[Clive FosterParticipant @clivefoster55965]

Andrew is correct in stating that toolholder positions should align with the tailstock socket. In practice not having tang location and being able to rotate the assembly could be an advantage. The tang on the MT mount of the hefty, professional, one I have for my Smart & Brown 1024 and Pratt & Whitney B locates it with the unused tools to the back of the bed. A decent idea in must cases but swinging things round by 45° to put them more or less upwards would make it far easier to tool clashing with the coolant pipe mount on the 1024. Plenty of room on the bigger P & W model B. As is I have to carefully set the cross-slide position before using the capstan and there are limitations when using longer drills. Sometimes I'm tempted to dig out the smaller cheap import I got in SouthBend 9" driving days which doesn't have a tang, just a round button, but it always looks silly flimsy to me. Works but care needed.

The 1024 tailstock barrel has both drift slot and self eject which, I think, is unusual.

Clive.

[Andrew TinsleyParticipant @andrewtinsley63637]

Hello Andrew,

Your capstan unit has the axis of rotation of the toolholding disc at right angles to the lathe axis. Mine is at approx. 45 degrees to the lathe axis, just like a dedicated capstan lathe.This explains the difference, I hope!

My apologies for not describing the turret alignment correctly in the first place!

Andrew.

Edited By Andrew Tinsley on 07/01/2017 12:06:09

[Andrew TinsleyParticipant @andrewtinsley63637]

Hello All,

I have made a big mistake! Andrew is quite correct in what he says, The tooling socket is always in coaxial alignment with the lathe (chuck) axis! Providing it is in one of the detent positions!

I had checked previously and for some idiotic reason thought that the axes did not align. So egg on my face and some embarrassment too! I think that my current medication has a lot to do with my errors. Maybe I should be very careful when using rotating machinery. The medication definitely says that I should not. A very depressing thought!

Apologies to everyone for time wasting,

Andrew.

[Chris HembryParticipant @chrishembry84309]

Posted by Andrew Tinsley on 07/01/2017 12:05:34:

Your capstan unit has the axis of rotation of the toolholding disc at right angles to the lathe axis. Mine is at approx. 45 degrees to the lathe axis, just like a dedicated capstan lathe.This explains the difference, I hope!

Not really, a production capstan lathe has the capstan pivoted vertically at 90 degrees. The bores are finish machined once fitted on the lathe to guarantee absolute axiality. If your capstan attachment is putting the tools out of alignment with the tailstock, it is at fault.

Regards, Chris

[Mike PooleParticipant @mikepoole82104]

Assuming the unit is made correctly, even with the capstan at an angle how will rotating it about the lathe axis change anything other than moving the error from say, the top to the side? I stand by my assertion that if it doesn't align then the problem is the registration of the turret or maybe the tail stock is not set true to the lathe axis?

Mike

Edited By Mike Poole on 07/01/2017 13:03:56

Just read your post Andrew, sometimes clarity of thought evades us, glad it has all fallen into place now.

Edited By Mike Poole on 07/01/2017 13:09:29

[EmgeeParticipant @emgee]

Posted by Andrew Johnston on 07/01/2017 11:12:03:

Posted by Andrew Tinsley on 07/01/2017 10:44:20:

Those of you who doubt that any alignment is required, please think again!

Really? It must be a very oddly designed capstan unit if by twisting it the selected tool moves off the axis of the lathe.

A properly designed tailstock capstan unit will have the axis of the indexed tool hole coincident with the axis of morse taper shank that goes into the tailstock. That being the case rotating the whole capstan unit doesn't change the alignment of the tool relative to the lathe axis. Always assuming of course that the tailstock is properly aligned with the lathe axis in the first place.

I don't have a tailstock mounted capstan on my manual lathe (I've got a proper bed mounted one) but I do have a tailstock capstan on the repetition lathe:

It doesn't need aligning.

It would be interesting to see a picture of your capstan unit, to see if it really does need alignment.

Andrew.

 

Andrew, the 8 tool turret shown in your pictures album demonstrates the need to locate the turret in the correct plane, otherwise why have a keyway groove machined in the turret mounting shaft ? The key will no doubt align all of the turret tool holders centres with the lathe centre when indexed to any tool position.

Emgee

Text edit

Edited By Emgee on 07/01/2017 13:15:05

[Tim StevensParticipant @timstevens64731]

Sorry to learn about the problems which Andrew ascribes to his medicine.

My medicine says in big letters: KEEP AWAY FROM CHILDREN

So I do.

Cheers, Tim

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Andrew Tinsley on 07/01/2017 12:31:12:

Hello All,

I have made a big mistake! Andrew is quite correct in what he says, The tooling socket is always in coaxial alignment with the lathe (chuck) axis! Providing it is in one of the detent positions!

I had checked previously and for some idiotic reason thought that the axes did not align. So egg on my face and some embarrassment too! I think that my current medication has a lot to do with my errors. Maybe I should be very careful when using rotating machinery. The medication definitely says that I should not. A very depressing thought!

Apologies to everyone for time wasting,

Andrew.

.

Not necessarily an idiotic reason … Maybe a recollection of seeing a Jacot Tool.

**LINK**

https://goo.gl/images/wollIo

MichaelG.

[Anonymous]

Posted by Chris Hembry on 07/01/2017 12:34:37

Not really, a production capstan lathe has the capstan pivoted vertically at 90 degrees.

For non-capstan lathes it seems to depend upon the whim of the designer, and on tool clearance. A bed mounted capstan with the turret at an angle has more clearance as the tools index round. For clarity this is an example of a capstan unit with the turret at right-angles to the bed:

Andrew

[Anonymous]

Posted by Andrew Tinsley on 07/01/2017 12:31:12:

So egg on my face and some embarrassment too!

I wouldn't worry about it; I'm an expert at making mistakes.

Andrew

[Anonymous]

Posted by Emgee on 07/01/2017 13:00:05:

Andrew, the 8 tool turret shown in your pictures album demonstrates the need to locate the turret in the correct plane, otherwise why have a keyway groove machined in the turret mounting shaft ? The key will no doubt align all of the turret tool holders centres with the lathe centre when indexed to any tool position.

Errr, I don't follow?

The capstan and indexing mechanism are mounted on a 'solid' collet. The grooves in the large diameter are the indexing grooves and index each tool location axially in line with the mounting collet. The mounting collet has a keyway, but this is a loose fit on the corresponding internal pin in the tailstock shaft. The capstan mechanism and shaft can be rotated several degrees before the collet is tightened. The collet is held in place with a drawbar similar to the R8 system. This may help illustrate the arrangement:

There is no external keyway in the mounting shaft. The only thing that stops the whole shebang rotating is the lever operating mechanism that mates with a pair of the series of holes to the right. As shown here:

The mechanism is pretty loose, so the capstan unit can rotate several degrees either way. Indeed it does so when operating, depending upon the direction of cut. However, alignment is not lost. I have never done anything special as regards alignment when fitting the capstan unit.

As an aside indexing is done when the capstan is pulled back against the tailstock casting. This pushes on a spring loaded lever which disengages the indexing pin allowing the capstan to be spun by hand to the wanted position.

Andrew

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