Production Engineering | Isambard's Lad

How to get better! Boot-strapping.

A tweet by @Therese_LW on Sir Joseph Whitworth the Victorian engineer reminded The Lad [@isambardslad] of an interesting question. It sparked off an Twitter thread with @BillHarvey2

Whitworth was an engineer close to Brunel in any global ranking. He made enormous strides in improving the methods and accuracy of machine tools. In general, he greatly improved the efficiency of engineering manufacturing techniques. In this work he drove the Industrial Revolution into a higher gear.

Screw threads are an enormously important factor in engineering manufacture quite apart from their use in a multitude of types of fastener. In the form of lead screws they not only allow heavy masses to be moved but also, in many types of machine tools, allows the distance of movement to be very accurately controlled.

A lead screw on a simple lathe is an important example of this. Here a cutting tool is usually mounted on a saddle whose position is governed by the lead screw. Such a machine can, using the lead-screw as a controller and via gearbox in the headstock, cut another screw thread.

diagram lathe — The parts of a simple lathe

The point here though is that a new screw cut on such a lathe cannot have a better accuracy than the lead-screw that controls the cut. It can only be, at best, as accurate as the lead-screw or, to some degree, worse. This seems to be a completely general feature of machining.

So, this is the question. How can you get from a screw thread that looks, in a wine-press of the early 18^thC, like this….

….to one that looks, and is, much, much more accurate like, for example, this lead-screw?

The Lad and @BillHarvey2 had an interesting, if rather compressed discussion on Twitter on the topic. He made the point that, in the early days, the toolmakers would have improved the shape and accuracy of a thread like the wine press or somewhat smaller, manually with hand tools like files and scrapers. This could then be a master screw to make others similar.

The Lad believed that there would be a limit to what could be done this way as the threads got smaller in diameter and the required accuracy increased. As was said above, you cannot expect to make an identical screw in a lathe that is better than the lead-screw you are using. It can only be as accurate or worse.

Then Bill Harvey gave what seems to be a breakthrough idea. A lathe is not limited to making screw threads that are the same dimensions as the lead-screw. So, let us fit our best, hand-improved screw as the lead-screw in a lathe. Then we set the lathe gearing suitably to cut a smaller diameter and finer [more threads per inch] screw. This way, the inaccuracies in the existing lead-screw will still be there but reduced in absolute terms in the new lead-screw. Fitting this new, finer and smaller screw back as a lead-screw in the lathe [probably a specially designed lathe for the job], we can then use it, with another gear change, to make a large screw again. This new one could be improved even more by hand.

Then this process could be repeated, with an improvement in accuracy each time, over several cycles of large to small to large threads. This is a boot-strap type process that seems to make possible an improved thread. There are other aspects perhaps such as a wide-span follower on the lead-screw as part of the improvement process.

All this so far though is deduction and an element of supposition based upon engineering judgement. The Lad must therefore check it if possible. First port of call will be “Sir Joseph Whitworth – The Worlds’s Greatest Mechanician” by Atkinson. See if that supports our deductions.

Thanks to @BillHarvey2 for the original discussion and the large/small thread idea and to @Therese_LW for raising the matter of Whitworth that sparked us off. Bill Harvey also posted on this subject.

The engineer’s new coin

It’s 1968 and the Decimal Currency Board is planning decimalisation. This group of the great and good wanted to get rid of the Ten Shilling note. Change it, they decided, to a new coin that had not previously existed and worth what is now 50p: a value greater than the then biggest coin. Now a bigger value usually means a bigger coin. Not a good idea this time though: for, to fit into the purse or pocket, it needed to be not too large or too damagingly heavy.

What’s to be done?

Through the ages, for every State and its Mint, resistance to the counterfeiter has been vital. But modern coins need another feature too. They need to operate vending machines and be suitable for bank counting machines.

Therefore, their weight and thickness have to have the right relation to other value coins. But the major criterion, by far, is that when you pop it into the machine, however a coin is oriented, the machine recognises its value because the coin width is constant.

Ergo, the coin has to be circular. Right?

One of the great and the good was Sir Hugh Conway. He was a top notch engineer, having spent most of his career designing aero-engines and was a recent past President of the Institution of Mechanical Engineers.

We mustn’t hold it against him that the company portrait gave him a strong resemblance to a Stage leading man of the 1950’s. Sorry, Sir Hugh.

Anyway, Conway was familiar with the processes used by his production engineers. They are the Company team who carefully engineer the methods for making amazingly-accurate engineering devices.

There are hundreds of different machining processes. Grinding is one way of making some highly accurate pieces. There are sub-types of grinding: some for flat items, others for cylinders.

Trying to avoid the cry, ‘Too much detail!’, The Lad resists the nerdy approach. One sub-type, see image below, squeezes the ‘work piece’ between two rotating wheels. The ‘moving’ wheel moves towards the other removing the metal; the other ‘stationary’ wheel rotates the work piece. As the machine removes material, the work piece will remain circular, won’t it?

No, not always. The work piece certainly does stay a constant width. So that’s circular, then? Not necessarily. If the engineers don’t set up the machine properly, the work piece will become – not circular but a lobed, non-circular shape. Certainly it is a strange shape but one which has a constant width. To the production engineers demanding a perfectly accurate, circular cylinder, this was nothing less than a pain in the butt.

To Conway though on the Decimal Currency Board, it was an opportunity. Make the 50p piece that shape and it will still work a vending machine while yet looking and feeling different to people.

Try this video to see a spritely take on the shapes.

To see this strange, lobed shape in real life, just look at a 50 p piece from your purse. Another thing is to put the coin on edge on a table. Then roll it, very carefully to stop it falling over, between a flat rule and the table. You will feel NO BUMPS at all. I guarantee you will think that your eyes are deceiving you.

In October 1969 the 50p coin was introduced, with the 10s note withdrawn on 20 November 1970.Now, in 2013 in the UK, the 50p is not the only coin this shape; the 20p coin is another. It was an announcement a couple of weeks ago of a new coin design that reminded The Lad of this story.

Not all think it was a good thing. Here is a ‘mint’ example of a truly ridiculous, bonkers, journo screed lauding romance apparently – by someone who does not calculate very much – his partner probably does it for him.

Engineering influences our daily lives in some ways that you may not expect. So, there it is: a new coinage by the engineer – both literally and metaphorically.

The Name of the Engineer

At the back of many of these posts lurks the definition as well as the name of the engineer. From the earliest posts to the more recent , The Lad implies a definition of what makes an engineer and what does not .

The core is that the engineer works with the various forces that exist in nature to turn them to the advantage of all humanity. At first, the ‘forces’ aspect seemed to be sufficient. Then recently he saw a newspaper [what else?] carry a picture of roustabouts on an oil platform and called them engineers. It is clear that they are vital workers, but, although central to the oil industry and estimable for their herculean work in terrible conditions, to all except the media they are not engineers.

From the newspaper — Such proud men probably do not call themselves ‘engineers’.

Why not? For aren’t they are wrestling with those natural forces in the massive rig and drill steelwork and the weather? Not half! Something similar can also be used to promote car mechanics to the ranks of engineers. A spanner and a hydraulic car lift certainly consist of natural forces, don’t they? They surely do.

The definition of the engineer, as The Lad knows her, needs to reflect how the roustabout and the mechanic are not engineers.

The mechanic and the roustabout do not design the equipment on which they work. This is the crucial difference.

The posts also implied that the benefit ought to be to all humankind. There are two difficulties here. One is to ask who knows whether an engineering artefact is really a benefit to all or only to some and also whether, in the long or medium term, it could damage. The other is that the engineering may be of benefit to some that are not of humankind. Think of a salmon ladder in civil hydraulic works or modern enclosures in a zoo.

Let us leave out Humankind. Let it stand as ‘benefit’ with the implication of ‘as best we know and can’.

So! Here we have it.

Update, June 22, 2013 – Realised that essential Production Engineering is not subsumed in the definition. To clear this most succinctly, the word ‘forming’ is added

Engineering directs for benefit any or all of the processes of imaginative conception, design definition, forming or analysis of devices or structures that use any of the forces acting in the universe.

3D Printing – Gift or the End of the World?

3D printing is appearing more and more often in the media. Admittedly, it is mostly in the more excitable screeds, but nonetheless a lot of people see it as a game changer. But then they would: writing about it makes media content to sell. A more technical name is stereo-lithography. This gives a clue as to how the idea works. It is like printing slightly different images on successive sheets of paper from your printer. Cut out each image and stack them up and glue them together and, lo, you eventually get a solid shape.

This is how the 3D process works. Image thanks to Materialgeeza.

Some internet enthusiasts claim that it will let anyone make anything and everything in their office or even their bedroom. “Buy nothing ever again: just copy it from the internet.” They are apparently almost wetting themselves in their excitement.

Others on the other side of the divide forecast the end of the world as we know it. Anyone will be able to make guns from freely available data files from the internet. Horrors! Even that device has to have at least one metal part – the firing pin. Made from a nail, since you ask. The Lad would be wary of going near to such a weapon being used, let alone lifting it near to his head and firing it at someone Wouldn’t you be wary of it exploding into a myriad pieces like an old blunderbuss? Or even one part splitting under the propellant forces, taking your face with it.

The fact that 3D printers currently cost a fortune and are large is the central problem at present. This may not always be the case though; they may follow the same path as computers whose prices dropped like a stone over the years. The picture is of a simple machine.

This is a simple version of a 3D printer. Image thanks to Bart Dring

Actually the idea has its uses now. No doubt more will appear in time. Because it is expensive and fairly slow and available only in a small range of not very capable or strong materials, its main use is to produce models of hardware straight from CAD designs on the computer. Prototyping it’s called: making model parts without complex machining set-ups.

OK. Let’s get down to the nitty-gritty-the essentials. Yes, it’s engineering again. It’s all about the material of the parts. How much of your world is made of plastic. Yes, quite a lot but nowhere near everything. Even in your computer, the heart of the nerd’s world, much is made of metal especially the strong, structural parts and the electrically-conducting parts. Most load-bearing things everywhere are metal. Of those that are not, the majority are composite materials; not yet possible stereographically. Also, see the gun firing pin mentioned above. Many of those metal parts have to be heat treated too to give them enough strength.

The Lad’s view is that it is likely that the process will be a nine-day wonder like fluidics. What is fluidics? A previous erstwhile Great New Technology that came to very little. Ask any engineer active in the Sixties.

OK, wait for The Lad to be proved wrong.

Dreamliner and a Nightmare

Who wants to be an engineer?

Boeing 787 Dreamliners are still grounded around the globe in February 2013 after the lithium ion battery problems became very bad in January 2012. Boeing says currently that it expects the aircraft to be back in service in late March or April. Something similar, but on a smaller scale, has happened before with laptops bursting into flames because of their lithium ion batteries.

This is the sort of problem that an engineer can face when any of her creations takes to the sky or arrives in numbers in the big, bad world. It may an aircraft, a car or a washing machine. It is what sometimes comes after the creative struggle of the Design process. Of course she hopes that the problems are not too terrifyingly large.

Now here, though, we have dozens of planes grounded for months and each worth two hundred million dollars [according to the Boeing website]. Nonetheless, dealing with similar things on a smaller scale are part of his job description for any engineer.

What information that seems to have seeped into the public prints is that the Lithium Ion batteries have not been adequately cooled and have taken fire. This is not something that aeronautical engineers want to happen to their babies. The aircraft designers or their colleagues, the Power Electronics Engineers, will be looking to see if some fault external to the batteries was the cause or whether the batteries installation has been designed too close together or whether the cooling systems designed for them are not sufficient.

The Lad is not a battery design expert, but he knows that lithium ion batteries are more like little furnaces rather than the EVEREADY, zinc oxide dry-batteries of his boyhood ‘tin’ torch. We can discover that like a boxer, pound for pound, these batteries are six times better than the standard lead acid battery in a car. This feature is gold dust for plane design engineers. But as a consequence of this, the lithium components are bursting with energy and therefore can get very hot. This, together with the essential [but flammable] solvent, means that a battery if it is hard-driven is continually on the verge of losing control to a runaway reaction and getting either very hot or even bursting into flames.

If it is a battery cooling problem for a modern airliner the solution will not be simple. No one can just say let us move them apart from each other or away from other bits of kit so that then they won’t get so hot. An aircraft may look large roomy and smooth from the outside.

An early DreamLiner at Farnborough Air Show

In truth, inside there is packed a 3D maze of structure, engines, fuel tanks and cargo…sorry, passengers. Below is a picture that gives an indication of the complexity of the structure even before all the rest of the kit is installed.

An early Production Engineering Test Rig

Agreed! It is not a very informative graphic but it is the only one that seems to be available. Remember, that the Dreamliner has much clever engineering to allow the use of vast amounts of non-metallic components in its structure. How they do this is a close Boeing secret and not one they are likely to share with anyone in public anytime soon.

Certainly, the plane will be crammed inside with frames and stringers between which the batteries will be shoe-horned into their position. What is to be done then in these jam-packed spaces? Currently, rumour has it that

“Boeing has proposed insulating the battery’s lithium-ion cells from one another to prevent fire spreading, encasing the battery in a fire-proof shell and installing sensors.
It also proposes a venting mechanism to remove fumes which led to the emergency landing.”

The view of The Lad is that this can only be seen as a ‘workaround’ rather than a definitive solution which should involve arranging for the batteries not to over-heat. We can only await events.

A final thought on those ‘events’ is that, if the experience of The Lad is anything to go by, major problems like this will be astonishingly more complicated than The Lad is able to deduce in this post. The points that he makes above will only be the beginning of the beginning.

Such problems will have a large team entirely devoted to solving them. Such a team will consist of dozens of engineers. There will be design and development engineers, metallurgists, electrical and electronic engineers. As a team, they will be working, certainly, seven days a week and probably 24hrs a day. That’s what engineers do: their best efforts sometimes produce a problem so then they have to race to solve it. All the while that they struggle, massive present and future costs result in cash haemorrhaging straight down the drain – to waste.

Note that, while Boeing may say all will be well by March or April, at least one major customer airline expecting to be without its planes till May. So – that the above Boeing team list does not include the groups of programme guys working at the airlines. They are struggling to arrange replacement flights for passenger already booked to fly in planes are no longer available. The costs of this group and plane hire will undoubtedly land on the Boeing doormat in due course.

It emphasises that the professional engineer must always work with not only the obvious factors of ‘materials’ and the ‘forces’ developed by the machines but also with essential factor of ‘finance’.

How about this thought though. Problems such as this Dreamliner may be exhilarating – provided no one thinks that you were to blame. If you are in charge of the team solving them, The Lad guesses, that it can be satisfying. So! If you are the person who says ‘Bring it on!’ then maybe you are a worthy successor to Isambard Kingdom Brunel.

Do you want to be an engineer?

Coffee Cups, a Cauldron and Containers

Gavin Turk told a newspaper [sadly, behind a pay wall] about a day in his life. He was one of the original Young British Artists and is a busy man employing several people. We learned about some of his past work. There were the 1000, signed sheets of paper each just marked with a ring from a cup of tea. Then there were the bronze casts of bite-marked, polystyrene cups painted to look real. He also took a single bite out of lots of Rich Tea biscuits (because, he said, of his interest in ideas about identity and how he could manipulate his image and name) signed each one and then sold them for £25 each.

The Lad looked up at the very moment after reading this piece. A shipping container on a lorry passed by the window.

Arbitrary Container — Engineers designed Containers like this one.

The conception, design and value of the container were different to Turk’s works. The concept and design of the container has transformed international commerce. That transformation, without exaggeration, is equal to the change from the stagecoach to the High Speed Train. That has changed the World. If you want to discover more about how it happened there is a very readable book. It is called “The Box. How the Shipping Container Made the World Smaller and the World Economy Bigger”. It is a marvellous story of how Containers did for shipping what computing did for engineering. Astonishingly there are no illustrations at all and only one simple graphic in the book and that is a line diagram on the title page.

One of the pleasures of the engineer’s tasks is the justified satisfaction in plucking out of her mind a design to do something and turning into a new object. True, the engineer is kin to the artist in that most artists also have a similar satisfaction in a task well done; that is of making something in their case mostly to give pleasure to the onlooker or to achieve a particular effect in their mind. It must be emphasised that there are occasions though when high artistry is vital. Even when it is not vital, it can still, combined with the right product or structure, add immeasurably to its quality. Few engineers can provide both qualities.

For the later, take the Olympic cauldron for London 2012 Games designed by Thomas Heatherwick. The concept needed an artistic intelligence of the highest order. It got it. Superb: there is no other word for it. First the artistic vision of many, separate petals: one for each of the countries taking part. Then the vision brought them together to become one cauldron. The engineering design then kicked in. It had to design the burners to produce the right flame picture; the fitting of the petals and the gas supply: the mechanism to raise them elegantly in synchrony into the air; to stand rigidly together in the stadium environment. A magnificent, dramatic blend of art and design.

Then there was the container that passed The Lad. Such ubiquity in modern life! Yet there is good engineering in this. You may argue that there is no artistry in the design of the shipping container. Even if you argue that fitness for purpose or form following function cannot be classed as such there is certainly intense creativity in its design. Then there are engineering drawings which have no artistic flourishes and are stripped down to the barest essentials to define any component or assembly of components. Nonetheless as an engineer The Lad finds in it, not surprisingly perhaps, a spare beauty. This is the General Assembly of a Shipping Container.

Standard Container example — An engineering assignment. "Design a Container"

One website sketched it as

20′ ISO shipping container, new
All listed shipping container types have a double door on one end which can be opened completely.
Walls made of corrugated steel sheets, profiled steel frames, wooden floor on steel cross members
certified by Germanischer Lloyd
steel plates made of Corten steel (anti corrosive)
forged and galvanised door locking bars

There is a Technical Specification here –

The heart of the design, however in the view of The Lad, lies with the corner fittings. They are not complex: they could even be called magnificently simple. They are the components that allow each container to be picked up and also to be firmly attached to the transporter or another container above or below itself. This is a drawing of one .

ISO Corner Drawing — The heart and core of the Container's design

Not all clever pieces of engineering are complicated. Some are quite simple. You will see that there are a number of holes or piercings in the corner fitting which are not circular. Each corner fitting is multiply connected as the mathematicians would put it. That combined with their need for some reliable strength makes their manufacture worth considerable thought. How would you make them? Machine them from solid? Or forge them? Stamp them? Weld them?

There is a good video talking of corner fitting features here by Tandemloc.

There is a hair-raising video showing the problems that the engineer seeks to design against here. Such a problem though is one of the invariants in any engineering design. Engineers load up a piece of the real world and any failures will have real consequences. Some of those consequences will be serious. Uncontrolled release of forces in the real world can have explosive effects; leading them to exert large effects somewhere undesirable – usually nearby. Such a risk is the shadow under which the professional engineer labours: it is for what she or he is paid. Every person in the world every hour of the day has to trust that they are successful.

Note that container corner fittings are actually cast and the cast components are then welded into the Container structure. Consider why this is so.

By the way, apparently, the Gavin Turk, Rich Tea biscuits are now priced at £108 on the Turk website. He does have insight about this though by saying that people would wonder why they should pay. The Turk response though clears that up because that’s what “I liked about it.” No doubt.

Does Gavin Turk find fulfilment in his daily work? Is he delighted (or at least, at the end of the day, reasonably satisfied) with having achieved something? More likely, he is punching the air at having discovered how gullible some people are. He must be having a larff (all the way to the bank).

Engineering is one of the three drivers advancing the human race. This blog describes real professional engineering as it is in the real world. It is not well served by the current media. An engineer is posting: not a ‘scientist’. Its target is the career seeker and also the general public.

Madeleine trumped by Ruby Loftus

Trefolex and Tufnol ride again in Mechanical Engineering 101.

Famously, the hero of Marcel Proust’s multi-volume novel, “A la Recherche du Temps Perdu”, found that memories of a period many years before were triggered by a smell and taste of tea and a dipped madeleine.

Immediately the old gray house on the street ….. rose up … and the entire town, with its people and houses, gardens, church, and surroundings, taking shape and solidity, sprang into being”
http://www.gutenberg.org/catalog/world/readfile?pageno=29&fk_files=1466063

Risking the bathetic after such a graceful idea and prose, The Lad found the opposite the other day: smells from his youth were triggered by this striking picture. It had been featured in a recent exhibition, Women War Artists (now closed), at the Imperial War Museum, London – website www.iwm.org.uk .

Reduced Ruby — IWM2850 Dame Laura Knight - 'Ruby Loftus screwing a Breech-ring'. 1943, Oil on canvas

Instantly, the workshop with its high roof appeared; it’s the Fifties. Machine tools are ranked in bays each controlled now by an apprentice in a white boiler suit. Each bay patrolled by its white coated Instructor. There was the low rumbling of the milling machines, the hum of the lathes just like the one in the picture, the hiss of the grinding machines. Equally pervasive was the smell of cutting oil and often the raw, burning smell of machined Tufnol – a composite material of linen and resin – still going It seems, [http://www.tufnol.com/tufnol/default.asp ].

But if it is a really vile smell you are after then it is in the fitting bay in the corner of the machine shop. Here are the benches and vices where there was hammering and a continuous swish of filing. There, on the bench were the pots of Trefolex, a thread-tapping paste, green coloured and with a vile stench. You can still get it today [http://www.warrenbestobell.co.uk/trefolex-cutting-compound.asp ] though they may have got rid of the smell by now.

The Training School entertained both Trade Apprentices and Technical Apprentices. The Trade Apprentices were being aimed at careers as skilled machinists; whereas the Technical Apprentices were intended for the draughtsman’s career. Notice the suffix ‘man’. No women or girls then in the Fifties: they were all long gone after the Second World War. Not even an office girl. “Disturb the youths, you know”.

But, contrary to the popular vision, the Training School does not represent the milieu of the professional engineer. It is Mechanical Engineering 101 where, then, he or nowadays often she discovers the basics before moving on. The mechanicals move on to design or work on new products for the machines to make, the production guys to introduce better machine tools or ways of dealing with difficult materials.

It was here, in the Training School, that The Lad first tried cutting an external screw thread on a lathe with a single point tool. He found it difficult while the Trade Apprentices seemed always only to thrive on the challenge. Then they moved on to using the same technique to cut an internal thread. This is what Ruby Loftus in the picture is doing: under intense pressure in War time using the high skill of cutting what would be a buttress thread for a breech block of an artillery piece.

This magnificent picture though is much more interesting than just for the memories of The Lad. The picture is, most importantly, but also so powerful, painted in 1943 the middle of the War, shows only a one male, a single small figure in the distant background. The thunder on the Home Front had changed everything. The painting of this picture shows that the changes were so radical that they had to be recorded. It was a peak in women’s employment never reached again even today. However, almost 70 years later, girls and women do take their proper place as apprentices and professional engineers.

The dignity of Ruby and her concentration on the complex machine and work piece stands four-square with the haughty gaze of Henry VIII in Holbein’s painting. http://darkpassenger.tumblr.com/post/727152626/hans-holbein-portrait-of-henry-viii-1537 The painter was Dame Laura Knight who had, pre-war, specialised in painting dancers and circus performers. http://www.damelauraknight.com/biography.html . Though less important, The Lad believes this powerful painting is also the most accurate, realistic canvas of a rare subject – a snippet of Production Engineering. Unless, that is, someone else knows better.

There is the contained poise and tension of the lean of Ruby. It is that of a dancer yet with stillness. Countering the figure of Ruby and closely observed, are the dark, gleaming masses of the lathe: the tool post, the carriage and the tail stock. The tools are there too: a scraper to remove burrs, an internal calliper for measurement, parting–off tools and tool holders and a ring spanner for the bolts on the carriage.

Ruby is gazing intently at the spot lit tool. It is cutting the thread inside the breech ring during the very brief period as the tool passes from the side of the work piece nearest her out of the side within the rotating chuck. Her hands are not just supporting her but a part of her vital control of the machine. She rests the fingers of her left hand on the tool post to check and confirm the faint, continuous, humming vibration showing that all is well with the single point cutting tool. Her right hand performs the same check on the gearbox driving the feed screw and confirms that the carriage is moving. That same right hand was also well placed to switch off the drive to carriage and work piece in an instant when it left the inside surface of the work piece before reversing it back out in the same helical groove of the buttress thread but with a slightly deeper cut.

Now, in the Twenty First Century, a CNC Turning centre does it all more quickly, just as accurately but with less involvement of a human operator – male or female.

Engineering is one of the three drivers in the advancement of the human race. This blog aims to give to career seekers and also to the general public a taste of how this might be so. They are not well served by the current media. It is an engineer posting: not a ‘scientist’. It describes real professional engineering as it is in the real world usually in the present and occasionally as it was in the recent past.

An Engineer’s must-have

It was years ago when The Lad first reached for the spanner for the usual 3/8 UN nut. It wasn’t there.

“What scruff [actually, a less repeatable name] has nicked the spanner?”

One of his compatriots had either left it lying around near where he used it last or nicked it for his tool box. In a busy workshop, it cannot be surprising if any tool goes walkabout. It happens even in the best, practical, production engineering school. But then everybody needed to use them so it was worth putting one that you have used back where it came from and everybody else could find it when they needed it. At least that’s what the instructors said – piously.

It was round about that time that The Lad first saw an advert for tool sets. The big ones with dozens of spanners within a steel tool box that attracted his covetous, young eye. The biggest and most complete ones even had castors as they were too heavy to carry. Have a look at one – product TKU 1014 at http://mdmetric.com/prod/kingdick/products/kd_toolkits.pdf ,
212 pieces and 67 kg! The Lad supposes that you could call it the secret of the engineer’s inner Nerd. But then who does not have such a secret?

Why so many pieces? Well, if the golden path and self-styled foundation of the modern world – Information Technology – can suffer from legacy systems even in its youth; then so can Engineering, that has been around many times longer. As well, the spanner has several forms for different jobs such as open jaw; socket; ring spanner etc.

The spanner is important to a mechanic. The screw thread has an ancient lineage and so has the regular shape of a nut or bolt head, most often a hexagon, that is required to manipulate it. Both are still ubiquitous in all engineering structures. The ancient lineage means that in its early days many different standard sizes of nut, bolt or screw were used. A major problem was that interchangeability of fasteners between manufacturers and machines was impossible.The thing about screw threads is that they are likely to be in use in some machines for decades or even longer. If you want to maintain one of those machines, you need a matching spanner.

It’s not just the diameter of the bolt that allows it to fit in a screw hole. Put simply it’s both the shape, usually a triangle, and also the depth of the spiral groove. The screw or bolt will not even begin to do its job if the bolt diameters match but both these features do not.

After an initial push in the early 19th Century when an accepted range screw thread designs that pairing a nominal screw or bolt diameter with a standard angle and depth of grooves was early seen to be useful subject for agreement between even competitive entrepreneurial engineering firms. A series developed by the great pioneer, Whitworth, and named after him became widely accepted. Around the same time also very widely used was the BA [British Association] series. This latter series had the advantage that the series went to much smaller diameters of screw which made it suitable for small instrument applications. The United States had its own, non-interchangeable series’s known as the US Standard developed by the engineer, Sellars. For pictures of any of these threads without The Lad infringing any copyright consult any engineering handbook.

It was only after the Second World War in the early 1940’s that further significant strides were made to reduce the still remaining variety of ‘standard’ designs. It was the unprecedented explosion of engineering production during and supporting the recovery after the war that led to the realisation of the serious inefficiencies and wasted costs were caused by the lack of an even more widely standardised, and interchangeable system of threads. At this the national engineering bodies of the USA and Canada and the UK came together to design a more rational series which they called the Unified series. Even this series was still restricted to the Imperial units of measurement. The final stage, to date, was to derive the ISO Metric series based upon the metric unit of length; that is the millimetre in the case of the thread. The Lad says the final stage but that will be completed only when everyone across the world uses the metric screw series. That’s certainly not easy and indeed he can’t say that it has yet happened. The USA still uses its standard AF [Across Flats] series widely.

The Lad has described a simple outline of the field. There’s a lot more to it of course: many professional engineering designers have to move, for good reasons, into much more detail such as fine and coarse thread series and limits and fits and indeed other more specialised thread forms such as ‘buttress’ and ‘knuckle’. Then of course there are the very different components called power screws……

As engineering is the most powerful and essential tool in the advance of human civilisation across the globe and the management of force is at its core; so the screw thread in its principal task of storing force grew to be and remains vital to most engineering structures and power plants. It is a most subtle adaptation of the wedge whose unknown inventor must be saluted as a genius on a par with Isaac Newton and above Leonardo da Vinci.

Catenary Support Eyesores

The Government has announced recently that £billions will be spent on UK Transport rail infrastructure. I assume that this will include the High Speed 2 plan linking London and Birmingham by electric railway. Those on the ground will always oppose the planned routes due mainly to the damaging effect on their house values.

But many also will cite visual horrors of the railway cutting through the contryside. The Lad, although an engineer, can understand that to some degree. The trains and their sounds are soon passed at any given spot. But the masts, skeletal arms and the wire arcs are permanently on display.

US array of cables — It should be possible to do better.

The Lad is not a catenary support designer but, in the UK, notes that it appears that standard RSJ uprights and other ugly components have been flung together. The idea?? of using standard parts or RSJ material is assumed to be the best way to achieve cost-effective structures. There does not appear to be any thought for the visual effect. See the pictures, which come from the excellent website, http://www.theoverheadwire.blogspot.com/ with the kind permission of its author Jeff Wood of San Francisco.

Second view of wire and mast array — Let’s design aesthetically better designs than this.

The Lad advocates a more holistic design. special components, possibly multi-use, could not only look better but also, he is sure, be more structurally and dynamically efficient. The cost of specially designed parts would not be more expensive. Why? Because in the hundreds of miles of line lengths there are multiple tracks and so there would be thousands of each given component. What happens to properly designed, component cost with large quantities? It plummets.

This post is The Lad’s quick response to a problem that has been irritating him in the back of his mind for some years. I will develop a strategy to try and move the idea forward. I will try to find the movers and shakers in this area and see if he can begin any sort of dialogue. The Lad will keep the blog in touch with any progress or none as transpires.

Making its Mark

Engineering was a craft before the Industrial Revolution but then much changed. Is this a “statement of the bleedin’ obvious” as Basil Fawlty would have said. No. I am not referring to the invention of the Steam Engine and the various weaving machines in themselves.

Simply put, it was the knock on effect, of interchangeable spares for those and other machines. Before the Industrial Revolution each machine was made by hand. Each of its parts was made to fit sufficiently accurately and smoothly with only the other parts of that particular machine. As more machines went into service and, with time, they needed replacement parts. It was expensive and a pain to have to go to the machine in question and make a new part to fit. Not only a pain: possibly in a working assembled machine it would be impossible to ‘find the sizes’.

Someone had the brilliant idea to make all the parts sufficiently accurately that any part would fit into any machine. The phrase “sufficiently accurately” is the secret here. All sorts of machine tools and techniques had to be developed to do the job but The Lad describes here only one.

Much increased accuracy was needed compared to woodwork. Before, wood could accomodate some inaccuracy due to its flexibility, lesser rigidity, and its usual static not dynamic function. Before you can make something accurately to size, you have to know what that size is [See my later post on the micrometer]. Then you have to mark the material accurately to that size. One component of the marking out process was actually a pair of items. The surface table and the scribing block.

The material that you are trying to make into an accurate component must be marked acurately, much more highly accurately than had been done previously. They need very fine lines permanently marked to a very accurate position. Then you can remove material to the marks. So: you stand the component on a very flat table usually made of cast iron, sometimes granite. If it is already machined, you may coat the surface with blue dye or copper sulphate to give a blue or coppery surface to make any scribed marks easy to see. A hard point mounted on a heavy block with a flat surface can then be set to a given, accurate height. As it smoooooooothly glides, steel on cast iron, over the table’s flat surface, it scribes a fine line on the material. Turn the component through a right angle, reset the scriber to a different height perhaps and scribe another line crossing the first. There you have it. At the intersection, is the place to drill a hole accurately in position.

The surface table is too big to form part of the current collection of The Lad. But the scribing block is not. Here it is in pictures.

lower pivot — The left thumb screw provides fine adjustment of the pillar and the right locks.© 2010

As well as the heavy base, note the heavy sections that give us a rigid structure. Under the small scribing load, this rigidity leads to almost zero deflection and thus mark-up accuracy.

Pins & vee — The pins have been pushed down through the base. The vee is for a cylinder mount.© 2010

Sometimes the engineer is scribing several parallel fine lines on a horizontal surface rather than a vertical one. If so, she can use the machined straight edge of the table using the pins pushed down as shown to run along the edge. Even a cylindrical guide to the scribing can be used if she finds it necessary by mounting the vee in the base on the cylinder.

Scriber mount — This shows the rigidity of the scriber clamp to the post. © 2010

Pins up and rainbow — A handsome protective finish on the base. The pins are up here. © 2010

The whole unit weighs 1.1kg. The makers say that this one was made around 1965. The surface finish shows a slightly raddled beauty: it must have been very striking when it was new. I asked the Wolfson Heat Treatment Centre what the effect was. Derek Close and his colleagues suggest that it was made by steam blueing, a process where a component at greater than 600 degC is immersed in dry steam.

The Centre is at http://www.sea.org.uk/whtc which operates within the Surface Engineering Association at http://www.sea.org.uk/

It certainly has some corrosion resistant properties. I say this because all but the, ground, corroded, lower surface of the base is steam blued and is not corroded.

This is one of the artefacts that The Lad collects. The essence of it is that it and the others in his collection are all things that The Lad has used albeit briefly. A scribing block has been around for a long time and its pedigree is tightly intertwined with engineering history.

This tool was called a “surface gauge” in the Buck and Hickman 1958 catalogue at £2.60. This catalogue is a weighty gem from The Lad’s 1960’s collection of engineering books. The Lad has always called it a scribing block so he will stick to that. Moore and Wright still exist by the way in Sheffield and Hampshire but are owned by Bowers Metrology Group [http://www.moore-and-wright.com/]. As an indication of a classic tool, the identical design of scribing block can still be bought new from Buck and Hickman that is also still thriving in 2010, http://www.buckandhickman.com/ . The current price is instructive though.