Stringer EW lathe

[alan smith 6Participant @alansmith6]

Edited By alan smith 6 on 24/08/2012 11:03:07

[alan smith 6Participant @alansmith6]

Hi,

I tried to upload a word doc for my last posting without success. What I had to do was print out the doc and then scan it in a pdf format which I then uploaded into the photo album and then I was able to upload the doc as a photo into the posting box.

The result was, as you can see, a reproduction almost too small to read.

Can anyone tell me the way to upload a word doc successfully into the posting box.

Alan

[Steve GarnettParticipant @stevegarnett62550]

Have you tried simply cutting and pasting from Word? If you use Times Roman, and a suitable font size it should work fine, but I think that there may be difficulties with a few characters. I never do this myself – I just type stuff in directly, like most people do.

[alan smith 6Participant @alansmith6]

Thank you Steve,

I find it easier to use Word for longer posts and thought that as the word symbol was on the top of the page I would copy and paste into the post box. I used Times Roman and font size 11 with no success. After pushing the copy button and then clicking on the "paste in from Word" button there was no response. I`m probably doing something wrong but I don`t know what.

Alan

[Peter TuckerParticipant @petertucker86088]

Hi Alan,

I copy from "MS word" just Ctrl A, Ctrl C in word then activate the posting box and Ctrl V. Some times a popup asks if I want the word document cleaned up, I click ok. No problems so far.

Hope this helps.

Peter.

[Sub MandrelParticipant @submandrel]

Hi Alan, Peter

The fifth icon from top left is a 'past from word' function that automatically cleans out dodgy formatting and presumably allows for Word's curious backwards use of return and newline…

Neil

[alan smith 6Participant @alansmith6]

Thank you Peter and Neil,

I`m working on a longish posting and will try your advice when it`s finished.

Alan

[alan smith 6Participant @alansmith6]

Hi EW Grafters,

Further to my previous posting where I expounded at length on the differences between the social conditions during the 1970`s and today, The nub of which was that today`s modelers are mostly much better off and certainly have a huge choice of new and second hand machinery to choose from than their fathers did in the 70`s The other main difference is that nowadays time is much more precious and some of the kit designed by contributors to the ME in the 70`s would be deemed too elaborate and work intensive by today’s standards.

As promised I will take a look at Martin Cleeves designs for the EW and hopefully make some sensible comments about them. We must not forget that Martin was being paid for his contributions and it did not harm his bank balance if the number of designs was more than necessary. I also wonder how many EW owners incorporated Martin`s designs into their own lathes as none of the photos in the thread display any deviations from the norm except for the countershaft which are all home made.

I already posted the impressive front cover heralding the coming of the Cleeve articles. Upon reading the articles I found that they mostly did not give a satisfactory explanation in the text of what was happening which would have probably deterred some beginners. I suppose that this was due to having to condense the articles to fit the space available. Any comments are my own opinion and by publishing them, I welcome any criticism by forum participants.

Starting with:

2926 Some Modifications to an EW lathe.

Her Martin puts forward the reasons for modifying the EW and shows before and after photos. The lathe in the unmodified photo is exactly the same as the one that was delivered to me in 1953. The modified lathe is mounted on a gigantic frame which is rather over designed. There is a shelf upon which are displayed like trophies, the products of his toils, which would be better put in a cupboard where swarf and dust could not get at them. The concept of the flat belt drive with fast and loose pulleys harks back to Victorian times and shows that Martin was from an older generation at the time of writing.

He captions a photo showing all his EW designs ”An orgy of fabrication” he wasn`t exaggerating!

There is also a close-up photo depicting the layout of the modified lathe clearly showing the ”grandfather clock” slow feed gearbox which would be better tucked around the back and a gear cover placed there instead to satisfy Health and Safety issues.

2929 The lathe stand.

Martin continues with the description of the lathe stand. Firstly he tries to justify his choice of a stand in preference to the standard countershaft layout and then trawls through his reasoning for the chosen pulley ratios to give a top speed of 1500 rpm at the lathe spindle. There is no photo, description or drawing of the motor installation. The sketch of the stand is shown with dimensions and a cutting list for the steel lengths.

I won`t elaborate more as I feel that this stand is completely irrelevant and a waste of time and money.

I will present a design to you combining both the countershaft and slow feed based on the original EW countershaft design shortly.

2931 A Saddle dead Stop.

This article in which martin describes an adjustable dead stop is enabled by replacing the original front spindle trunnion bolt by a new bolt which has a square head drilled to receive the round bar which is the stop and a tightening clamp screw with handle and ball which works by deforming the hole in which a slot has been made.

I do not approve of this for two reasons, the first because it disturbs the setting of the spindle front trunnion, secondly because if the saddle is run into the stop during slow feed it could damage something, which Martin does warn against in the text.

I have had stops on my various lathes over the years but never used them because of the possibility of damage. I used the calibrated dials to calculate distances, it worked for me!

In my book, all this is unnecessary work.

TO BE CONTINUED

[alan smith 6Participant @alansmith6]

2936 Improved Fixing for the Leadscrew Nut.

In this article Martin makes a different fixing for the leadscrew nut which increases the travel of the cross slide slightly. For me the gain does not warrant the time spent. In a later article Martin describes making a longer tee-slotted cross slide, put the time into making this.

I seem to remember that I made some spacers which I inserted between the cross slide front plate on which the feedscrew is mounted and the cross slide itself. This seemed to do the trick without all that palaver.

2941 How to Make Ball Handles.

Martin devoted a whole article to making ball handles. One can easily see how to make matching handles by looking at the ones already on the lathe. This article is really superfluous as far as the EW is concerned.

2942 A Leadscrew clutch.

Martin puts down his ideas for a dog clutch in the leadscrew that could be used during screwcutting or when using the slow speed for the saddle. This is really a ”must” for the EW.

However there are some points about Martin`s design that I don`t approve of. The most unusual point in my eyes is the method of attaching a trunnion to the lathe bed to support the split leadscrew which is done by drilling a hole in the lathe bed casting. Also to avoid any keyways in the clutch, Martin designed the part of the leadscrew, which incorporated the drive, to move in and out of engagement as a whole, which means that the gear on the end of the leadscrew slides back and forth whilst in mesh with the idler gear.

I really can`t bring myself do this on my lathe as it upsets my Engineering sensibilities, all I can say is that Martin did not look long enough to find a proper solution.

I will submit my amendments for the clutch when I can get to the drawing board and do the drawings.

2952 An Independent Feed for the Saddle Part 1.

In this article Martin gives his reasons for designing a gearbox for the slow feed. As usual he designs something completely feasible but which in my opinion lacked in-depth thought. I`ve already given my reasons in a previous posting but to re-iterate, the ”grandfather clock” gearbox would have been better located behind the headstock so that a cover for the headstock gears could be fitted. There is also a problem in driving the gearbox if the longer spindle, which Martin proposes in a later article, is not fitted.

Included in this article is a screwcutting chart, this was never provided by E W Stringer as far as I know. As well as cutting the threads mentioned in the Stringer catalogue one can also cut 9, 11 & 13 tpi.

2955 An Independent Feed for the Saddle Part 2.

This continuation describes and provides sketches for the gearbox construction and to bring home to the reader the danger of the saddle accidentally striking the adjustable stop, Martin recommends that a 3/16” spring belt be used so that it will slip to avoid damage in such an eventuality.

Obviously in the light of this information Martin was not advocating a heavy cut when using the slow feed. Better not to fit the saddle stop and take some decent cuts. I rest my Case.

I will be submitting a design for a ”gearbox” as mentioned in a previous posting.

TO BE CONTINUED

PS. It worked thank you.

Edited By alan smith 6 on 27/08/2012 23:08:36

[Michael GilliganParticipant @michaelgilligan61133]

Just a couple of thoughts …

Looking at the Exactus article; the Ratchet [which is, quite reasonably, worrying folks], is a modified 55 tooth changewheel driven by a long rod from an Eccentric.

1. I suspect that this will run more quietly than you fear … whilst I have done no analysis of the mechanism; it does look much more "progressive" than simple Pawl.

2. There are plenty of small Stepper Motors available [typically salvaged from Printers] with 48 steps per rev. and it would seem a very simple matter to replace the Ratchet with one of these.

MichaelG.

[alan smith 6Participant @alansmith6]

Thank you MichaelG for your erudite posting, I suppose like a lot of "golden oldies" I have not embraced the electronic age. There is a difference between submitting an idea and making a practical solution for the application of that idea.

I suppose the stepper motor would have to be mounted somewhere so we would have to know the size and rating so that it can be placed without affecting the other workings of the lathe. A mounting bracket would have to be designed, an electrical supply would have to be created and switchgear put in place. Frankly I don`t know how to do this, so would you please put some flesh on your idea so that we can all see the potential benefit to our EW`s.

Alan

[Michael GilliganParticipant @michaelgilligan61133]

Alan,

Thanks for the kind comment.

I will try to post something regarding motors and controllers, this evening.

If the concept looks good to you, then EW Owners will need to design a suitable motor bracket … I regret that I am not a member of that elite club.

MichaelG.

Edited By Michael Gilligan on 28/08/2012 12:53:56

[alan smith 6Participant @alansmith6]

Excellent MichaelG,

I look forward to seeing your solution as it may be the way forward for us.

Just a quick word to confirm the actual operation of the slow feed. The idea is to have the leadscrew rotate at a speed relative to the actual spindle speed, in this case we are looking for around .002" of feed per rev of the spindle and the exciting thing for me is the possibility that the rate of feed would be easily adjustable by some means which I`m sure that you will tell us.

I anticipate that the motor will drive the leadscrew as already proposed and there will be a clutch of sorts to be designed, probably based on the Cleeve dog clutch, as with the Exactus clutch a screwcutting indicator will be required. We will have to do a torque test on the leadscrew with the lathe under a reasonable cut on steel just around the belt slipping torque to determine the torque of the motor required.

Alan

[Michael GilliganParticipant @michaelgilligan61133]

First thoughts on updating the Exactus Fine Feed:

The Eccentric drive and Ratchet arrangement is very ingeneous; but I believe it could usefully be replaced by a simple pulse generator, driver circuit, and stepper motor.

The new generation of stepper motor drivers is extremely efficient and very easy to implement.

For our purposes, the best option is probably the A3983 from Allegro Microsystems.

This extraordinary little device takes all the hard work out of the job. [for a full description, see the dataheet hyperlinked above].

The device comes as a "Surface Mount" package, and the thought of soldering it would worry most of us!

Fortunately, it is readily available built into a plug-in module … and we only need basic soldering skills to complete the job. Modules are available from several suppliers, but I have been very impressed with the JAFmotion MicroStep.

I won't labour it here … the details are on the website, and it really is as easy as it looks!

Highlights are:

Wide voltage range

Presettable current

Choice of stepping modes [full steps, 1/2, 1/4, or 1/8 steps]

Stepping mode can be changed whilst the circuit is powered.

So far as I can see; the only way to destroy this is by disconnecting the motor whilst powered.

Power requirements are 5V for the circuitry and something suitable for the motor

… I start with 12V, but the chip can handle up to 35V.

Both voltages are DC, and various laptop or games console power supplies may be suitable if you don't want to build one.

A pulse generator might be as simple as a Reed Switch, actuated by a small magnet.

… There are numerous alternatives, according to taste.

As supplied, and without additional cooling, the A3983 will safely drive up to 1.2A per phase.

… This is sufficient for a surprisingly powerful stepper motor.

Now to Stepper Motors:

For years these were a mystery to many … not least because of the wide variety of wiring arrangements.

Anything between four and eight leads, and no apparent standard for the colour code.

It's much easier now, because A3983 and similar are BiPolar drivers [i.e. the outputs change polarity], and we only need connect four leads to the driver: The others are either joined together, or left unconnected, according to the impedance that we want for each phase [happy to explain this further if anyone needs help].

So [assuming we use A3983] we need a stepper motor with four or more leads, that will provide adequate torque when pulling no more than 1.2A. There should be plenty to choose from.

I have put some photos in an album, showing an old Burroughs Dot Matrix printer that I stripped for parts. Both motors are 48 steps per rev, but the coil impedances are quite different … one is 8.5 Ohms per phase, the other is 50 Ohms per phase. Note that there is no voltage specified.

These are "tin can" motors, simply fixed via two screws.

The other standard frame is NEMA, which comes in various frame sizes; the most likely candidates being 17 and 23

Note that these are usually 200 steps per rev.

… There are useful details in [for example] the ArcEuroTrade catalogue.

Sorry if this post is a little disjointed … but hopefully there is enough to spark some interest.

If someone could please check what torque is reasonably required to drive the leadscrew, then we can make some informed choices.

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

A note about NEMA:

Most drawings show the mounting holes on a square pattern, dimensioned as rectangular coordinates.

Regardless of the units chosen, these will always look inconvenient [unless grossly approximated].

The reason is very simple …. NEMA originally specified the mounting centers [*] in fractional inches, equispaced on a pitch circle.

MichaelG.

 

[*] NEMA is an American association, so we should grant them the spelling.

Edited By Michael Gilligan on 29/08/2012 08:13:25

[IanTParticipant @iant]

I've been watching these postings with great interest, particularly the very useful discussion of the electronic replacement of the proposed pawl arrangement.

Quite apart from my EW – I also have an Adept hand shaper – and had looked at the various arrangements for automatically stepping the head so far published. They all involve a pawl-type arrangement of some sort e.g. a mechanical stepping drive. On the Adept I have developed a two-handed method of pulling the handle and turning the feed-screw simultaneouly but it is far from convenient (or comfortable) and I had thought of a stepper-drive solution but never got beyond "thinking about it".

There are probably quite a few situations where a very simple (e.g. not full CNC set-up) stepper motor on a single axis would be very useful gaget. I'd like something that stepped so many (adjustable) steps on a 'go' pulse (microswitch). If it was a 'portable' unit – I could use it on the Adept, the EW and perhaps on other things – rotary table for instance? A small black-box and a simple way to attach/remove a stepper motor in 2-3 minutes (via an Oldham coupling?) would make it multi-usel and not overly expensive

Just some more food for thought!

Regards,

IanT

[Michael GilliganParticipant @michaelgilligan61133]

An excellent idea Ian …

A while ago, there was a suggestion [see this thread] that people engage in some sort of "Open Source" design project. This might be the ideal project.

MichaelG.

Edited By Michael Gilligan on 29/08/2012 09:16:33

[Michael GilliganParticipant @michaelgilligan61133]

Posted by IanT on 29/08/2012 08:58:25:

I'd like something that stepped so many (adjustable) steps on a 'go' pulse (microswitch). If it was a 'portable' unit – I could use it on the Adept, the EW and perhaps on other things – rotary table for instance? A small black-box and a simple way to attach/remove a stepper motor in 2-3 minutes (via an Oldham coupling?) would make it multi-usel and not overly expensive

Ian,

Whilst we are pondering … Toothed belts are a very useful alternative to the in-line couplings.

We could have a flanged pulley on the drive module, and [appropriate ratio] plain pulleys on each machine. …. That's versatile.

MichaelG.

[IanTParticipant @iant]

Well great minds (OK – this maybe an exageration in my case) think alike Michael – I was just checking the belt used on my Taig milling head.

It's a 'Gates 3M315' – 3mm wide/narrow and very strong. They are available in various lengths – so yes – I think that would be a very simple way to do it on reflection. Also some form of 'gearing' (2:1) on the pulleys would help increasde the torque available.

So that's sorted then – you design it and I'll build one!

I'm pretty sure David would also like an article about it in MEW too!

IanT

PS Looked at the JAFMotion device and it seems to fit the bill – and it's even within my price range – even better!

[Michael GilliganParticipant @michaelgilligan61133]

Posted by IanT on 29/08/2012 08:58:25:

I'd like something that stepped so many (adjustable) steps on a 'go' pulse (microswitch).

 

Ian,

Have a look at Electrozone UK … Their ESMC-02 driver is VERY clever

… It's only 750mA current, but might be just what you are looking for.

MichaelG.

Edited By Michael Gilligan on 29/08/2012 09:46:20

[IanTParticipant @iant]

Sorry Michael – just re-read your post.

You meant a toothed belt – e.g. timing belt.

Yes that might be better – I was thinking of something simple (and slim) – the pulleys for the Gates belt would only be about 5-6mm thick – excluding any need for a 'boss' – and would be (are) simple to turn from ali plate. I guess it depends whether slip would be a problem or not. Not on the EW or Adept applications probably – but more so on a rotary table.

Just a small detail really and perhaps more a matter of the actual application/space available. But a 'belt' attachment method is the way to go (or at least the way I will go!)

Ian T

[IanTParticipant @iant]

And just looked at the ESMC device too Michael – downloaded the date sheet. Even I may be able to figure this out as it gives various wiring set-ups

Would the ESMC unit handle sufficient current to power a large enough stepper? (how large is large enough?) .

At £40 for this device, say £30-40 for a stepper motor and something for a PSU it would be about £100

Need to read the datesheet and think about how I'd use it.

IanT

[Michael GilliganParticipant @michaelgilligan61133]

Ian,

Personally, I do prefer toothed belts [timing belts] for this sort of application, for peace-of-mind.

… also, they often only need to be very lightly tensioned.

There are very small versions available [look inside any modern flatbed scanner], and:

To a man with a Shaper, knocking out flangeless toothed pulleys would be a doddle.

Good to hear from you … let's keep this going!

MichaelG.

[alan smith 6Participant @alansmith6]

Ian & Michael,

I think that we already are participating in an open source design project, the cross fertilisation of ideas is always beneficial.

What this thread is leading up to is a common direction for our endeavours. For the torque measurement probably IanT is the person most enabled to do this, as unlike myself, he has a working lathe, so what about it Ian, can you do this for us?

Michael, you gave us a lot of information in your posting which, alas, I was unable to immediately comprehend, I will have to do a crash course in stepper motors and their control.

Ian put his finger on the essence of what we want, which is a simple deign for the feed only. not full CNC.

In order to help myself and probably others, I will put down my expectations from the stepper drive and let MichaelG tell us whether my expectations can be fulfilled. Then we can get down to the nitty gritty of the design itself.

Firstly to see whether we need a leadscrew clutch, can the motor be instantly reversed? If it can, then we could probably do away with the clutch.

Can this reversal be controlled manually? This is to do away with the complication of micro switches or their modern equivalent.

To get the feed relative to the spindle speed, I assume that there will be some kind of optical device mounted on the headstock somewhere which sends a signal to the control box for the motor. This feed rate would be around .002" per rev of the spindle, which would be approximately 6 degrees of rotation of the leadscrew but I would expect that this rate of feed to be immediately adjustable to suit the type of material being machined.

In my experience simplicity is king and I see in my imagination that the motor would be controlled just like a model train set. All we would need is a forward, stop and reverse switch to control the feed with another rotating switch to control the speed of the feed. Perhaps we should choose a motor with more torque than initially deemed necessary, so that we would then need a way of controlling the torque of the motor.

All one would have to do is to set the spindle speed, switch on and bring the tool to the work by means of the leadscrew handle, set the cut and then switch on the feed. At the end of the cut the feed would be stopped and either reversed at a faster rate by the motor, or reversed using the leadscrew handle.

There you are Michael, can this be done?

Alan

 

 

 

Edited By alan smith 6 on 29/08/2012 10:29:22

Edited By alan smith 6 on 29/08/2012 10:34:27

[Michael GilliganParticipant @michaelgilligan61133]

Posted by IanT on 29/08/2012 10:08:14:

(how large is large enough?) .

That's where we need some torque measurements, from various machines doing various jobs.

e.g. What torque needs to be applied to the leadscrew of an EW lathe, to take [say] a 0.02" deep cut in various materials at a feed rate of [say] 0.002" per rev of the workpiece.

Note: for those so inclined … Metric approximations are welcome

Must go for now; I need to tidy the workshop.

MichaelG.

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