Project for a Double End Lathe

Friends, I am planning something surprising, shocking, stupid maybe. It’s about a conventional machine tool, namely a double end lathe. Such an apparatus has a number of possibilities over the well-known asymmetrical lathe.

I have a mate who has a shop and needs work. Now, I am more the thinker while he is clearly the doer. Not that I am not capable of making chips and burrs, it’s also more the situation of mine inasmuch that I’m having time which he isn’t. The idea has been swirling around in my head for a year or two now. Of course did I do some research on the subject and as the situation presents itself there are only very few if not one single maker, namely in the empire of the middle.

A double-end lathe basically has a central, rather short, spindle with some means to clamp pieces and two carriages to both ends. Once a piece is set into rotation one can give both ends of it a flat face, a center, and so on. More or less symmetrical pieces are thus very quickly prepared for subsequent operations between centers, in one setup. Centers are very well in line with each other. From a little delibaration one understands that it is wiser to move two tools parallel from the machinist’s point of view, not in opposite directions. One would employ a RH and a LH center drill for that reason, a right and a left turning tool. There’s worse.

So here’s what I’d like to know from the sage and wise forum: Do you see a chance for a medium size product of that kind? Do you believe it could have a chance when being of a conventional concept with possibly mechanical feeds, say swappable cams? What if I’d aim at a heavy old-time cast iron layout, preferably heavier than today’s fashion, actually a long lasting product made to be easily maintained? I’m thinking of a two-inch spindle through right now.

Consider a mid lathe chuck and two tail stocks at each end and a tool post at each side. Perhaps a collect holding might be better than a chuck..Yes it might face, center drill and turn a diameter and a thread to each end. How straight might each end be to the center portion? with being automatic each end might be done at the same time.. manual and a wait for each side.

Might be good for a special machine to run a production part but for jobber work I think not such a good machine.

Perhaps a double tool holder to run two ends of parts at the same time might be good. Yes double lead screws and the works..Yes likely best for between centers work.... and perhaps center drilling on another machine.

I think it would be a pain to load with a tail stock in the way at each end.

likely a center rather short spindle machine to turn two ends at once would have made if such was a good idea. I am having difficulty seeing the use.

You mean like these, only smaller?
Lodge&Shipley double-end axle lathe
Bridgeford and L&S double-end axle lathes

Seems like a machine to solve a specific problem. Given the bottom has fallen out of the market for manual lathes of more general sorts (both of mine are full manual, not my fault. ), I don't think a smallish double-end lathe is an idea that will revolutionize the market. Especially since a CNC lathe with robot or a CNC lathe with subspindle can handle most of the jobs that a double-end manual would do.

sfriedberg said:

You mean like these, only smaller?
Lodge&Shipley double-end axle lathe
Bridgeford and L&S double-end axle lathes

Seems like a machine to solve a specific problem. Given the bottom has fallen out of the market for manual lathes of more general sorts (both of mine are full manual, not my fault. ), I don't think a smallish double-end lathe is an idea that will revolutionize the market. Especially since a CNC lathe with robot or a CNC lathe with subspindle can handle most of the jobs that a double-end manual would do.

Click to expand...

+1 They don't make much sense at less than a foot in diameter thru-bore, preferably twice and more of that.

"Back in the day" it had to do with reducing sag, bending stress, and the time and monkey-motion need to counter it with rests and their re-positioning, most especially if all, or nearly all, of the work was to be done only at or near the ends, and/or.. the work was so long it even had to be re-positioned, one end on roller rest, not centers.

In their element, they would have been four or more times as fast as same work done on a large enough 'conventional' lathe, yet required less floorspace.

Time has marched on. There isn't a lot of such work left around.

At TWO INCHES? There never was...

I'm sure who the target customer would be. It solves one problem while creating others.

Strictly from the perspective of bar end preparation, an HMC does this very accurately and efficiently.

Mechanola,
I can't help with your new design, but I recall some double-ended lathes have been discussed before. I can't now find the thread with one lathe I recall (not a big axle lathe, but a 'normal' workshop lathe, say 6" centre height).

I did find one lathe, seen at Naysmyth's works in 1856. This was posted by Asquith in post #287 of his epic "Galloways" thread. Image from Asquith's Photobucket. The post said that one young boy was operating both ends of the lathe turning bolts.



http://www.practicalmachinist.com/v...oways-rolling-mill-engines-146469/index8.html

Peter, thank you for this

Werkzeugmaschinenbau Sinsheim – Fit fur die Zukunft. ...

My idea is of a smaller entity than this CNC one.

Just think of the possibilities, you have a chuck and two tailstocks. At least one of them must go out of the way which is, I think, not too fifficult to accomplish. One possible system would provide a swing-back feature. To center a part longitudinally is done by the aid of two movable wedges. The chuck is exchanged by a collet spanning unit.

One doesn’t need to do identical work on both sides, neither at the same time. The very point of the arrangement is that both sides are accessible in one clamping. Add a tailstock, you can work on pieces shaped like that ├-----------. Second operations are not on an end. Unless one wants to grind center bores for ultimate precision a piece given centers can also be taken to grinding, say only a roughing.

I know that demand for new manual machines is ephemeral. Some conventional machine tooling will remain in use, though, hopefully with professional formation.

That Nasmyth’s would be good if CNC so one could load a part while the other was being turned… certainly might save floor space.

We used to do that on a horizontal mill.. Load the other part while milling the first.

Note that the Nasmyth double lathe is a double or twin lathe, not a double end. You have two chucks with independent belt pulleys and centers.

Like the others, I see this having a very, very limited market. You have described the potential advantage - being able to work on both ends with one chucking. But let's also describe the accompanying disadvantages:

1) You can work on the ends, but not the middle. So if you are making a shaft, for example, you're still going to have to remove it from the chucks to get to the middle section ... and even if you now have beautifully prepared centers for center-turning the piece, you also have a lathe that is only half as long as the floor space that it occupies to try to turn between centers. In other words, you might have to move it to another machine to finish the middle features.

2) And do you actually wind up with beautifully concentric centers? When you chuck it in the middle, you are going to have to make sure that it is chucked concentrically, presumably with a chuck on either side of the drive. If you're using 3-jaw chucks with .005 runout on each end, then you could introduce a .01 wobble to the piece just between the two chucks ... and out at the ends of the piece, the wobble could be ... let's just say, interesting. So instead you'd probably need to use 4-jaw chucks or adjustable chucks of some sort to get your piece concentrically lined up, so that you actually wind up with concentrically machined ends. And frankly, that sounds like a BIG hassle, particularly compared to the old fashioned way of putting in a center on one end, and then turning it between centers.

No doubt there is some highly specialized need for which the benefit outweighs the deficits -- just as the lathes pictured in the posts above were apparently specialized for a certain type of rail or locomotive work. But is that specialized need going to provide a sufficient market to support the cost of development? I note with interest that among the hundreds of used lathes that I have seen for sale, not a one has been one of those double-ended variety ...

Oil country lathes have a chuck at both ends of the headstock to steady long joints of pipe, but if there were a tailstock or tools at the back end you couldn't load the workpiece. Something would have to swing out of the way, and then there would be repeatability issues.

Every once in a while I used to obsess over an idea for a manual machine tool, like a bench-size lathe with a three-inch hole thru the spindle--on the theory that there has never been a lathe whose spindle hole was big enough to be convenient--but the day for stuff like that has passed.

Mechanola, if we had been young and ambitious in 1900 we'd have all been great captains of industry.
And sometimes I think I'd like a do-over of high school, but then I figure I'd have ended up the same, so WTF.

+1 on the multiple good caveats mentioned.
A good option for similar work is an automated dual spindle lathe, with 1 or 2 Ts.
These exist as cnc.
As in 2 primary spindles (and or 1 or 2 secondary spindles (with +/- TS support)).

Even better with dual-cutting options on the spindle 1, if possible.

A manual dual-end lathe would run fine, of course.
Face both ends independently.

For accuracy, later, one could
center-drill them as needed, if needed, run between centers, if needed,
and one more op to turn OD true.

But, imho.
Complex.
Has mechanical constraints, possibly.

Has no profitable economic benefit, imho.
It will never be a super-fast manual machine for making say boat drive shafts or something semi-accurate.

If You build it to be a super-accurate machine (perfectly doable, imo, ime), it will be expensive.
So, again, where is the beef ?

E.
There are lots of corner cases where something unusual is profitable.
-
I no-quoted one, and recommended a competitors (MS) japanese turning center to a customer, once.
They needed very fast reliable production of one part, for 3M units over many years, no variations.
No spec, accuracy, drawing, etc. just do-as-it-falls-cosmetically-good.
(Casket rails.)

It was a very special case, where the More Expensive machine was the better choice for the customer, cutting 2 ops/op, reducing cycle time by 70%.
And is what we told the customer.
"We don´t think we are the right choice on technical reasons, and do not recommend our stuff for this app., and as such do not have an offer at this time."

On some quotes, some potential customers were upset.
These were on 500k$+ deals.

I had to explain;
- look, whatever I sell, I am responsible for.
No matter what the contract says.
I don´t want You to blame me, later, for x, or y, or z, publicly.

- We cannot as a company (a global major MT dealer) fade from responsibility.
As such, I will not take risks, for Your deal, if my engineers do not think it is a good idea.

Eg2.
- I / we think Your idea on a,b,c (long live tools in major production to very high TIR/accuracy requirements, 600 mm deep to 0.01 mm TIR), will not work in production.
We do not wish to sell such tooling. (Tooling was from major global brands, to their spec.)
Tooling deal was == 200-300k€.


I personally learned a lot from that time.
The best stuff was that many customer want what is not possible.

And just like in other sectors I have lots of experience with, the earlier You tell the potential customer no, the easier it is.
The harder You say no at first, the better.

Soft-stepping things makes the customer expect stuff, but for I/me/You as a provider to not get any cash ever, and for both parties to spend lots of time, money, effort and executive energy on crap.
Do not do it. Just say no.
"We cannot, afawk, deliver abc as You currently want it."




REALLY IMPORTANT:
All the good executives/owners/principals always liked a fast no-way response (or ok, can be done for x $$$) on tech/money/possibilities.

Mostly, the execs and hang-arounds and managers always saw me as a dangerous liability, focused on reality and technical execution vs political-correctness and supporting existing supply-chains.

This made my principals over 2M£ in a short amount of time, for example (4 months).
All who hired me, made lots of money.
Unfortunately, I was mostly toxic with local managers, later on.

A usable wheel already exists. Doing both ends at the same time means that the parts need to fit your machine. Twin turret sub spindle lathe could do the same thing with one huge advantage. First spindle set up with bar feeder, second spindle set up with parts catcher. Bar stock goes in, finished parts come out. Finished parts of most any length. Unless you have invented the ".500 thick powered head-stock. Then I bow to thee.

Thank you everybody, very interesting contributions

Those who follow me a little will recognise that I think like an engineer from 1920. Double-end lathe, axial chuck, clockwork movie cameras, and manual. Thanks again

A double lathe to face and center a short parts with having manual load with a chuck, tail and tool post to the left to only CNC face and drill center one end at a time then manual turn part for other end..., and a CNC part center held lathe to the left to run part features. Yes like two lathes on a common bed.. the advantage being a short distance to load second operation and operator only has to load not think about operation except to tweek program and change inserts, and all machining being done at same time, and save floor space. Disadvantage almost as costly as twe lathes.. and limited part length.

Yes some swiss (and the like) machines can flip the part and do all this on a single lathe.