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John Stevenson
11-07-2009, 12:46 PM
The YATSDRO thread brought this back up in my mind.

Years ago someone came up with a design and it was widely copied and went down in time as the de facto design, the tailstock is one of these, not a ot you can do with one given that it has a ram, should be parallel and on centre and has a method of feeding forward.

This gives a loose set of constraints like the feeding forward, internal thread, external thread, hand wheel, lever or a mixture but they still do the same thing.

Now take the method of controlling it's travel as regards non rotation. This is usually something simple like a pin or a key that slides in a horizontal groove in the ram.

Given that depending on design we have plain beds, dovetail bed, double dove tail and all forms of keep plates and scraped surfaces to give a sliding surface with no play it amazes me that no thought was ever given to the tailstocks problems.

A sliding fit is easily obtained by precision boring and honing but anti-rotation is taken care of by this silly pin or key. The carriage is prevented from lifting by scraped and robust surfaces even though cutting forces are bearing down but the poor little orphan tailstock has to rely on a pin or key possibly 1/10 the size of the tang of a drill.

We are told that it's not the tangs job to do the driving but that is handled by the taper but anti-rotation is handles by this silly little pin.

Now take something like this:-

http://www.stevenson-engineers.co.uk/files/tailstocklock.jpg

Using a robust key that goes down onto, or close to the centre line of the ram it will have a far greater surface area to prevent the ram from rotating, counter rotation will be controlled by the side of the key.

It would be a relatively easy job to machine as all the surfaces are on plane lines respecting to centre lines or parallel.

Not shown is the metod of securing the key as there are many ways to do this and some can even have a degree of adjustment built into them.

Flames, bricks, used 20 notes all appreciated.

.

PeteM
11-07-2009, 01:02 PM
Sad comment on the state of the US economy, that there was no mention of bedraggled $20 notes.

See your point about a tiny key handling all the drilling rotational forces. But, is it a problem? Personally, I've never had a tailstock key shear. Wear, yes. Shear, no.

Alistair Hosie
11-07-2009, 01:09 PM
used 20 notes all appreciated

hey John that's not fair I was first.:D:DAlistair

GadgetBuilder
11-07-2009, 01:25 PM
Occasionally I need torque in the other direction from the tailstock so it seems like the ram's anti-rotation scheme should be symmetrical.

Something like a regular square key with a screw to keep the key from migrating out might work for this and should be more robust than the pin scheme. Would require slotting the base for a short distance to hold the key. A key should survive most any torque applied since the force to shear it would be considerable.

John

dp
11-07-2009, 02:15 PM
If the key were on the other side it would be held in place by forces on the quill. If the key were on both sides you could turn left-hand acme threads as well as right-hand, using a dead center.

If the keys were horizontal it would help keep crud from dropping, and help keep crud from gathering on the cutout.

Replace the keys with adjustable gibs and you have an interesting tailstock. Add a motor to the screw and you have a new CNC dimension.

John Stevenson
11-07-2009, 02:34 PM
No Dennis it is on the right side as it's looking from the front. Cutting forces want the take the barrel in the same rotation as the chuck, clockwise viewed from the front of the tailstock.
With a close fitting key it can also support on it's side for LH threads.

.

Black_Moons
11-07-2009, 03:26 PM
How about a V wedge with a flat bottom like an ACME thread form? into the 'center' of the tailstock ram, With two set screws to adjust it in as it wears, Vertical walls into the tailstock part but the acme threadform into the ram part.

dp
11-07-2009, 03:34 PM
No Dennis it is on the right side as it's looking from the front. Cutting forces want the take the barrel in the same rotation as the chuck, clockwise viewed from the front of the tailstock.
With a close fitting key it can also support on it's side for LH threads.

.

I've annotated your tailstock image - the arrow shows the direction of rotation imposed by work held in a dead center. The view is from the headstock end. I've also relocated the key. In this image it seems the key and quill are self-locking, no?

http://TheVirtualBarAndGrill.com/machinery/tstock/tstockkey.png

malbenbut
11-07-2009, 03:40 PM
To make a long wedge type key slot may be expensive to manufacture or machine. Cost of pin probably 2 pence to make, cost of additional metal to accomodate wedge pin, machining long key may cost 50 pence.
Machine manufacturers don't like anything new or costly, lathe designs have hardly changed since 1920.
MBB

J Tiers
11-07-2009, 08:41 PM
I have no clue why the round ram has lasted so long, when there were shapers and slotters to look at for better ideas.........

I posted a longer comment in the other thread, the gist of which is that rams are not supposed to spin, so what Einstein decided they should be round?

You can't gib them without a lot of effort, so from day one they get looser and looser, and nothing you can do about it.

Ken_Shea
11-07-2009, 10:21 PM
I have no clue why the round ram has lasted so long, when there were shapers and slotters to look at for better ideas.........

Sure you do, 1st, they are the least expensive solution, that's the bottom line, 2nd, make changes to what people are expecting to see and they will endlessly question the wisdom.

Paul Alciatore
11-08-2009, 04:44 AM
As can be seen from reading the David Gingery books, if you are building a lathe from scratch, the round shape of the tailstock ram is a great aid as the tailstock can be line bored after the headstock is working and it will be dead concentric with the headstock. So it should be no surprise that this shape was the first to be used. The fact that it works is good reason to keep it. "Don't fix it if it isn't broken."

As for the antirotation pin, it also is a simple solution that just plain works. A 3/16" or 1/4" diameter pin of a good grade of steel has considerable sheer strength. And all it takes to install it is a drilled and perhaps tapped hole.

I don't understand the idea that the tang on a taper is not for driving it. What the heck else is it for? If you answer it is for extraction, I will say that a simple pin on the small end of the taper is a lot simpler and will work just as well. I have installed such extractor pins on tapers that didn't have a tang and they work just fine. I say the tang IS for driving the tool. It really is!

Black_Moons
11-08-2009, 05:15 AM
Most lathes don't have anything to 'recive' the tang and drive it. Drill presses often do however.
Some lathes (cough mine) require the tang to be ground down a a little bit or it prevents the tool from seating in the taper correctly.

ptjw7uk
11-08-2009, 05:54 AM
Just a quick thought on this, why does the barrel have to be round - if it was square you could then shim it and it certainly wouldnt rotate.

Just a thought.

Peter

Weston Bye
11-08-2009, 06:45 AM
Sad comment on the state of the US economy, that there was no mention of bedraggled $20 notes.

See your point about a tiny key handling all the drilling rotational forces. But, is it a problem? Personally, I've never had a tailstock key shear. Wear, yes. Shear, no.

Done it a couple of times - 'course, was with an Atlas 6" lathe. The anti-rotate key is just a 1/8" roll pin. The little pin was not man enough for the 9/16 drill bit I was using.:o

J Tiers
11-08-2009, 09:34 AM
Sure you do, 1st, they are the least expensive solution, that's the bottom line, 2nd, make changes to what people are expecting to see and they will endlessly question the wisdom.

Read comments in other thread.........................


So it should be no surprise that this shape was the first to be used. The fact that it works is good reason to keep it. "Don't fix it if it isn't broken."

it's broken. You can't ever adjust it "in" after its loose, but for every other part of the lathe you can make adjustments and correct alighnments. The ram is the ONE place where nothing can be done except a major re-bore and sleeve, etc.



As for the antirotation pin, it also is a simple solution that just plain works. A 3/16" or 1/4" diameter pin of a good grade of steel has considerable sheer strength. And all it takes to install it is a drilled and perhaps tapped hole.

The PIN is plenty strong, or can be made so. and anyone who thinks about it for a minute will add a support lever anyway, riding on the topslide etc. I use a lathe dog, typically. The problem is as much the fact that the pin often is NOT "made so", AND that a simple pun will beat the jheck out of the guide slot. A long key would be lots better, but isn't always used.

[quote]
I don't understand the idea that the tang on a taper is not for driving it. What the heck else is it for? If you answer it is for extraction, I will say that a simple pin on the small end of the taper is a lot simpler and will work just as well. I have installed such extractor pins on tapers that didn't have a tang and they work just fine. I say the tang IS for driving the tool. It really is!

The tang *can* drive, but the friction of the taper is the real deal. The harder you feed, the more it grips. The tang will be twisted off if that is the sole drive. I've seen tangs that look like pretzels on account of that. It sure wasn't because the shop dog chewed on them.

AND I have a couple drills that DO just have a pin on the back.... looks like they were made that way, it wasn't just a modification.

lazlo
11-08-2009, 09:42 AM
I have no clue why the round ram has lasted so long, when there were shapers and slotters to look at for better ideas.........Sure you do, 1st, they are the least expensive solution, that's the bottom line, 2nd, make changes to what people are expecting to see and they will endlessly question the wisdom.

There must be more to it than that. Megabuck price-is-no-object toolroom lathes like the Schaublin, Monarch 10EE, Hardinge HLV, Cazeneuve, ... had round tailstock quills.

All those machines had unique, some say weird, features that defied conventional wisdom.

The first thing that comes to mind is fitting a square quill to the bore. The tailstock socket/bore (don't know the proper term) is honed to fit the quill within a couple of tenths. I don't know how the heck you'd do that with a square quill.

My Bridgeport slotting head is one of the very few machines I've seen that has a square quill. It has a long flat gib on one side to center the quill, and even then, I doubt it's centered particularly accurately.

J Tiers
11-08-2009, 09:47 AM
The first thing that comes to mind is fitting a square quill to the bore. The tailstock socket/bore (don't know the proper term) is honed to fit the quill within a couple of tenths. I don't know how the heck you'd do that with a square quill.


thinking IN the box still.............

Who says the ram has to be enclosed? Is there a federal law?

it could be set up similar to a bed turret ram, for instance.

And even in a square hole, you can gib it on two sides. That takes the need for tenth fitting away, and substitutes merely being flat and straight. Lathe builders are typically fairly good at flat and straight.

John Stevenson
11-08-2009, 09:53 AM
The first thing that comes to mind is fitting a square quill to the bore. The tailstock socket/bore (don't know the proper term) is honed to fit the quill within a couple of tenths. I don't know how the heck you'd do that with a square quill.



Look at some of the power hacksaws, they had two square rams carried in split housings that were easily milled or ground using a normal cutter of grinding wheel set over at 45 degrees.
They were often built with shims to control wear at a later date and remember these did more sliding work that a tailstock would ever do.

.

lazlo
11-08-2009, 09:54 AM
thinking IN the box still.............

Who says the ram has to be enclosed? Is there a federal law?
it could be set up similar to a bed turret ram, for instance.

I was just brainstorming ideas why lathe designers haven't used round tailstock quills.

The best and brightest machine designers for the last 100 years haven't used them on lathes, despite being used in other machines. So square quills were well-known, and on toolroom lathes cost was not an issue, so what was the reason?

J Tiers
11-08-2009, 10:14 AM
Some things , no matter how smart, just won't be accepted by the prospective purchasers.

"it's always been round".......

"our competitor's square ram can easily wear out of alignment or become loose".......

"boring a round ram bore on the machine it will be used on ensures concentricity, unlike our competitor, who assembles theirs in a different part of the factory and hopes they are concentric when some random tailstock is put on the lathe you buy............"

"why has nobody else tried that if the round ram is so bad? Generations of machines have proven it best........."

All bogus, but all sound good if pitched by a good salesman. Tradition is great, you don't have to argue FOR it, it is ASSUMED valid and best, you must prove the contrary..

lazlo
11-08-2009, 10:22 AM
All bogus, but all sound good if pitched by a good salesman. Tradition is great, you don't have to argue FOR it, it is ASSUMED valid and best, you must prove the contrary..

I don't buy it. Look at some of the crazy (innovative) features on those toolroom lathes: hardened toolsteel bed (beds should be made from Cast Iron! :)) and Turcite-lined saddle on the Hardinge, ancillary ballscrew with a captive nut for power feed on the Schaublin, the powered tailstock on the Cazeneuve, the odd sloped, "double-height" bed, aluminum apron and wildly complicated electromagnetic gearbox on the Graziano ...

wierdscience
11-08-2009, 01:40 PM
What about those huge roll turning lathes like the Binns Superlathe that feature square tailstocks?

Fully adjustable and able to carry huge loads.

J Tiers
11-08-2009, 08:59 PM
I don't buy it. Look at some of the crazy (innovative) features on those toolroom lathes: hardened toolsteel bed (beds should be made from Cast Iron! :)) and Turcite-lined saddle on the Hardinge, ancillary ballscrew with a captive nut for power feed on the Schaublin, the powered tailstock on the Cazeneuve, the odd sloped, "double-height" bed, aluminum apron and wildly complicated electromagnetic gearbox on the Graziano ...

Better get out yer money.......

ONE company can do anything, the true test is if anyone else picks it up.

And, you can do a lot of things if it still LOOKS the same.....

it's easy to list the problems of a round non-adjustable tailstock ram.

It's also easy to show that a better design would not have those problems. But, it would not be possible to have that sort of tailstock and have it LOOK like a standard lathe. It will look different, and look is what drives people.

if it LOOKS odd, who wants to be the one to spend a lot of money on it and maybe find out it has bad problems?

"Yeah we had to let him go, he wasted a bunch of money on a crazy lathe with some newfangled bright idea for a tailstock. None of our toolroom guys would use it, they said it was too strange. Cost us a bundle, and we had to sell it off cheap. He sure did like anything new and weird, but we need to make money."

Black_Moons
11-08-2009, 10:01 PM
How about we fix the problem then?
Someone here must be willing to make and sell some tailstock sized/shape raw castings.
Most people really into it seem to have the 12" or 14" swing lathes, ways vary but as I said, we would be milling it ourselfs.

johnnyd
11-08-2009, 11:25 PM
It seems to me that the simplest solution to ram wear, would be the addition of a simple "oil fitting" on the tailstock casting...along with a "spiral" groove on the inside of the tailstock bore. Sort of like they used on some of the old "babbit" type bearings years ago.

Peter S
11-09-2009, 07:06 AM
I don't buy it. Look at some of the crazy (innovative) features on those toolroom lathes: hardened toolsteel bed (beds should be made from Cast Iron! :)) and Turcite-lined saddle on the Hardinge, ancillary ballscrew with a captive nut for power feed on the Schaublin, the powered tailstock on the Cazeneuve, the odd sloped, "double-height" bed, aluminum apron and wildly complicated electromagnetic gearbox on the Graziano ...

Lazlo,

Sorry to veer off tailstocks (though it will touch on more important ways of updating the "lathe as we know it"), but I don't like to see Graziano mis-represented. Aluminium apron?? You must be joking, Grazianos are made from cast iron and hardened and ground steel, maybe an aluminium name plate or bezel or something like that, I can't recall any aluminium parts at all.

The double-height bed is truly a great leap forward because it allows the main bed ways to be covered in a most simple way, so Graziano ways cannot get swarf on them and they last forever if lubed. And of course the design means they have a huge natural gap. The Graziano bed shows how a modern lathe should be designed in my opinion, other types covered in swarf are just primitive in comparison.

When you work in a toolroom with a line of top quality lathes to choose from, the electro-magnetic gearbox is what makes a Graziano the first choice by toolmakers I have worked with. I am not exagerating, they are exceptionally good, and just darned good fun too. :) And very reliable and long-lived. I have one made around 1974, the electric transmission (or the whole lathe) has not been touched or had a cent spent on it.

By the way, Graziano made a line of lathes, and only the smallest model (SAG 12) had an electro-magnetic transmission, the other, larger models of the range had conventional manual-change gearboxes. They are great too! :) Later, it seems the SAG 210 came along with electro-magnetic clutches too, it was not part of the range that made Grazianos name in the 1960's and 70's.

Seriously, I think Graziano made sensible attempts at building a better, modern lathe for the end of the 20th century, they really had some improvements over the old that went before. The electric trans idea might scare you, but I can start the lathe, change gear four times, put it into reverse and change gear four times in the time it would take you to possibly change one gear in your manual clunker. Imagine how great that is when screw cutting, to be able to speed up to a shoulder, slow down, reverse out, speed up, slow down etc, all with a simple clicks all on the single 'stick' that controls everything. Its fantastic! A Reeves drive (e.g. Colchester Chipmaster) is a bad joke in comparison.

Oh, and a Graziano tailstock will never wear out, or break its large square "pin", its made for life.

Rif
11-09-2009, 09:53 AM
I have been wondering why most new lathes have the option to have a tailstock turret. (There is one exception, that I can think of. It looks like a Hardinge clone.)

lazlo
11-09-2009, 10:03 AM
Lazlo,

Sorry to veer off tailstocks (though it will touch on more important ways of updating the "lathe as we know it"), but I don't like to see Graziano mis-represented. Aluminium apron?? You must be joking, Grazianos are made from cast iron and hardened and ground steel, maybe an aluminium name plate or bezel or something like that, I can't recall any aluminium parts at all.

Peter, I wasn't conjecturing :) John (Texas Turnado) just disassembled his SAG12 to send the bed off to Commerce Grinding, and was surprised to find that the apron is cast aluminum.

I have the pictures that John sent, but I'll let him post them. If you PM me your email address, I'll forward them.

John, want to comment?

lazlo
11-09-2009, 10:23 AM
Seriously, I think Graziano made sensible attempts at building a better, modern lathe for the end of the 20th century, they really had some improvements over the old that went before. The electric trans idea might scare you, but I can start the lathe, change gear four times, put it into reverse and change gear four times in the time it would take you to possibly change one gear in your manual clunker.

Oh, absolutely. I think Steve (S_J_H) summed it up well: the SAG's electromagnetic gearbox is machine art :) That's why I used it as an example of machine design innovation!

TexasTurnado
11-09-2009, 10:56 AM
Lazlo,

Sorry to veer off tailstocks (though it will touch on more important ways of updating the "lathe as we know it"), but I don't like to see Graziano mis-represented. Aluminium apron?? You must be joking, Grazianos are made from cast iron and hardened and ground steel, maybe an aluminium name plate or bezel or something like that, I can't recall any aluminium parts at all.



Sorry to disappoint you, but my SAG12 definately has an alumunum (definately not iron or steel - it's non-magnetic and lightweight) apron. I was vey surprised also, but there it is:

http://i288.photobucket.com/albums/ll168/TexasTurnado/PA170060.jpg

My first tip-off is when I lifted it - surprising light. Then I noticed no rust anywhere on it - so I did the magnet test....

I agree it's a great lathe - any idea where I might find parts like way wipers? I had to have the bed ground because of excessive wear - I'm not sure if the ways were not lubed or the PO was grinding on it. The way covers are missing leading me to speculate they were taken off to clean out the accumalation of something (grit?) and not replaced...

Here's a couple more shots:

http://i288.photobucket.com/albums/ll168/TexasTurnado/PA170062a.jpg

http://i288.photobucket.com/albums/ll168/TexasTurnado/PB020020.jpg

lazlo
11-09-2009, 11:19 AM
John, for those who aren't familiar with the SAG -- explain how the apron joystick works. That is so cool!

BadDog
11-09-2009, 12:00 PM
Going further OT, I'm also curious about the often mentioned "natural gap". Seems to me that's nothing more than a discontinuation of the upper tail stock ways, and really no benefit at all compared to a traditional bed of equivalent capacity where the TS rides on lower ways. And while I do like the raised TS ways and associated built in way covers, they don't extend to the place most needed, that being the "natural gap" area.

As for "lasting forever", I looked at a local SAG-12 some time back (before I got my current 17). I passed in part because of obvious wear near the headstock, though otherwise the machine was in great shape if it had not been for poor storage conditions.

That said, I do love the SAG design.

lazlo
11-09-2009, 12:09 PM
As for "lasting forever", I looked at a local SAG-12 some time back (before I got my current 17). I passed in part because of obvious wear near the headstock, though otherwise the machine was in great shape if it had not been for poor storage conditions.

Notice the grinding marks on John's SAG. That's post Commerce Grinding (this is a lathe from Reliable, after all...). They took off between 5 - 8 thou. John's getting really good at Turcite :)

TexasTurnado
11-09-2009, 05:46 PM
John, for those who aren't familiar with the SAG -- explain how the apron joystick works. That is so cool!

The joy stick is a joy to use.... :) It rotates on it's own axis to select one of four speeds using the electromechanical clutches mentioned earlier - and it also rotates up or down at the end to select the direction of rotation via two more of the electromechanical clutches. There is a button on the end of the joystick for braking, which turns on both the forward and reverse clutches at the same time (or so I've been told). You can see it on the right side of the apron in the first picture I posted with speed numbers around the skirt.

The four gears and six clutches are located at the bottom of the headstock end and three v-belts drive the headstock proper. Either standard or back gear speed ranges are selected in the headstock, giving a total of eight speeds. Here is a photo of the headstock end:

http://i288.photobucket.com/albums/ll168/TexasTurnado/PA090044.jpg

The little copper pipes are from the high pressure oil pump and provide oil to both ends of the clutched gearbox

TexasTurnado
11-09-2009, 05:56 PM
Going further OT, I'm also curious about the often mentioned "natural gap". Seems to me that's nothing more than a discontinuation of the upper tail stock ways, and really no benefit at all compared to a traditional bed of equivalent capacity where the TS rides on lower ways. And while I do like the raised TS ways and associated built in way covers, they don't extend to the place most needed, that being the "natural gap" area.




The "natural gap" is a result of truncating the tailstock ways short of the headstock by approximately the width of the saddle. If the ts ways had been extended all the way to hs, the swing would have been limited to approximately 12 inches (hence to "12" in SAG12). As it is, the swing is something over 17 inches until the ts ways start.

BadDog
11-09-2009, 06:43 PM
Thanks, that's what I was thinking. So it's roughly equivalent to a 17" lathe that has TS ways in the normal location, though without the larger spindle. Nice lathe you got there...