Iain Macleod

BS 8888: 2011

2011-10-28T00:18:00.000-07:00

We (that is committee TDW/4/8 at BSI) have recently finished putting the final touches to the next revision of BS 8888. With the new revision, why have tried to do something significantly different with the standard, which we hope will make it much more useful for industry.

BS 8888 first appeared in the year 2000, when BSI withdrew BS 308 and adopted the ISO system of standards for technical specification.

The ISO system for technical specification is documented in a large number of ISO standards (probably around 250 in total). At present this is like a large, disorganised technical library, consisting of numerous documents from different authors with very different styles of writing. Some documents provide a broad overview of a large area of technical specification, while others go into minute detail in a very specialised topic. Some documents deal with specific manufacturing processes, such as casting and forging, while others deal with general topics such as dimensioning or drawing views. Some documents have overlapping content, and in many cases, you would have to use two or three documents together to properly understand a particular topic.

ISO are making some efforts to bring structure and organisation to this collection of standards, but this is a slow process, and will take many years.

BS 8888 was introduced to help engineers work with the ISO system, and initially did so by providing an index, along with some additional commentary to help explain some topics.

With the new revision of BS 8888 we are taking this a step further. There were two fundamental reasons behind our approach to the new revision:

Industry has in many cases found BS 8888 unsatisfactory to work with, because they expected BS 8888 to be a replacement for BS 308, and to contain the same level of information. Some poor marketing from BSI early on encouraged this misperception, and the subsequent disappointment felt by many who purchased the standard.
The ISO system is difficult to work with because of the way in which it is spread over a wide range of different standards, which are interrelated, but often in a fairly haphazard manner.

Our aim within the technical committee has been to use BS 8888 as a vehicle to address both of these problems.

In order to make the ISO system more accessible, we have taken the core content of a number of key ISO standards, such as ISO 1101 and ISO 5459, and incorporated it directly into BS 8888. In this way, we intend to make the essential elements of the ISO system available together within a single document.

In order to make the ISO system more useable, we plan to use BS 8888 as a filter. We will include the main elements of the ISO system, which are relevant to most users, but screen out some of the more specialised aspects of the ISO system, which would have very little relevance to most engineers (and would only tend to confuse matters). BS 8888 will continue to index and reference all these ISO standards, but the aim is to maintain a central body of content which provides access to the fundamental elements of the system.

The 2011 revision of BS 8888 is currently scheduled for publication in December. It is not perfect, but we hope that does mark a significant step forward in terms of the usability of both BS 8888 itself and the ISO system.

I will lay out some of our plans for the further development of this standard in a future post.

ISO 8015 & ISO 14405

2011-07-02T02:39:00.000-07:00

First the bad news. With a couple of minor tweaks, none of which addressed the fundamental objections put forward by the UK and USA, ISO 8015 has now been approved. The UK, USA and Canada all opposed this, but it was passed with a comfortable majority of other nations voting in favour. The invocation principle, which requires all mechanical engineering specifications to be interpreted according to ISO GPS rules unless an alternative standard is specified, is now enforced. The voluntary nature of standardisation, which has always applied in the past, has in this case been removed. You no longer have to opt in to the use of this standard, you now have to opt out, which places a responsibility on anyone involved with mechanical engineering specifications to be aware of the standard and its rules.

With the new version of ISO 8015 now published, much of the content of the previous ISO 8015, dealing with size and the envelope requirement, has been moved to another standard, ISO 14405-1.

ISO 14405-1 is the first standard to really address the whole issue of size properly, and gives a thorough, and long overdue, breakdown of the different ways in which size can be defined. It also provides tools which enable size to be defined in different ways on a specification when necessary. In the absence of any other indication, the previous definitions of size still apply by default.

This is a good standard, which brings clarity to an area of specification which is often poorly understood.

There is also in the pipe-line an ISO 14405-2 standard. This is really concerned with explaining how a specification will inevitably be ambiguous if datums and geometrical tolerances are not used. The UK felt that this content should be produced as a technical report rather than a standard, as it is really just an informative document, but again were over-ruled. However, the content is perfectly valid, and may be of interest to anyone who is not convinced of the necessity of using geometrical tolerancing to specify products.

Multitasking

2011-05-02T07:52:00.000-07:00

An interesting article here, suggesting that while we are all under constant pressure to multitask more and more, it may not be a good idea.

http://www.pbs.org/wgbh/pages/frontline/digitalnation/interviews/nass.html

see what you think ...

Symbols

2011-05-02T07:50:00.000-07:00

Mas'ood asked about some of the symbols I mentioned in the last post. I'm working on a document to publish here which will show where all the different symbols are to be found in the ISO GPS system. Real soon now!

Paris and Helsinki in February

2011-03-23T04:23:00.000-07:00

February was a busy month for travel. The ISO TC 213 conference was held in Paris, so I was there for five days. At one meeting, with a fairly tight schedule, it was tentatively suggested that lunch could be restricted to 50 minutes, but the French delegation vetoed this idea immediately. They take their lunchtimes seriously over there.

I also had to deliver a geometrical tolerancing course in Espoo, just outside Hesinki in Finland. Helsinki in February rarely gets warmer than -20C, so that was an interested experience. Many of the cars have cracked windscreens over there, which I assumed was due to the extreme temperatures. However, locals told me that it is nothing to do with the temperature, but due to spikes from snow tyres being flung up from the road. They went on to point out that you never see motorcyclists in Finland in the winter!

The picture on the left shows the view from the back of the training venue. This is on the coast, and between the camera and the trees in the distance is an inlet from the sea, but completely frozen at this time of year. Just behind the 'stop' sign on the left of the picture, you may just be able to see a boat frozen in.

On one evening we went to the Zetor restaurant in Helsinki, which has an unusual kind of farming theme. Some of the tables are built onto old tractors. Farming implements cover the walls. Old buckets are used for lampshades. The food was very good.

Common Zone modifier

2011-03-21T05:08:00.000-07:00

First post since November! It has been a busy few months, but I must try to do better than that. I'll put up some more posts about what has been going on shortly.

Mas'ood occasionally sends me interesting (or awkward, depending on your point of view) questions about geometrical tolerancing.

I am going to put some of his questions here - feel free to comment if you have a view.

First question is about the use of the 'common zone' modifier, CZ.

This is placed in a geometrical tolerance frame to indicate that two or more features have to satisfy the requirements of a single tolerance zone.

CZ used with a flatness tolerance

Mas'ood's question was whether the CZ modifier can be used with the envelope requirement.

Personally, I don't see why not.

ISO devised the CZ modifier with a view to it being used in the tolerance frame only, but as long as the meaning is clear, I see no problem with applying it to the envelope requirement as well. It would be a way of indicating that two features-of-size, of the same size and in alignment with each other, should be treated as a single feature.

CZ applied with the Envelope Requirement to two features

I would feel less comfortable with this approach if it was being applied to two features which were produced with separate machining or manufacturing operations, but we are well into the realm of 'designer's descretion', as the standards provide no guidance in this area.

CZ applied with Envelope Requirement to two features produced with separate operations

ISO have developed several different symbols in recent years, such as Common Zone (CZ), Separate Zone (SZ), United Feature (UF), Contacting Feature (CF), etc, and are currently reviewing these to see if they can minimise this 'symbol inflation'. The 'UF' symbol was to be used to indicate that several features were to be treated as if they were a single feature, but ISO TC213 will be reviewing whether the CZ symbol could be used as an alternative, or even remove the requirement for the UF symbol altogether.

FDIS 8015 gets negative vote

2010-11-06T02:48:00.000-07:00

The Invocation Principle - see previous post - was part of the latest revision of ISO 8015. The FDIS (Final Draft International Standard) of 8015 has just recently been out for vote, and the results are back.

In order to be approved, two thirds of member organisations must vote in favour of the FDIS (66.66%), and no more than 25% of members must vote against. The actual results were 65% in favour, and 32% opposed. The FDIS has thus received a negative vote, and has been 'disapproved'.

Phew! But far too close for comfort!

The Invocation Principle

2010-11-01T11:22:00.000-07:00

How do you know which standards govern the interpretation of a specification, such as an engineering drawing? That is the problem that this principle is intended to address.

When we had our old British BS308 standard, it was easy. You were asked to put a note on the drawing along the lines of ‘DRAWN TO BS 308’. With the new British Standard, BS 8888, we suggest a similar note, such as ‘CONFORMS TO BS 8888’, and the Americans require that drawings produced to the American standard show a reference to that standard, ‘ASME Y14.5-2009’.

ISO have never had a formal method of indicating that drawings or specifications conform to ISO standards. One of the key ISO standards is ISO 8015, which defines the Envelope Requirement and how size tolerances are interpreted. ISO 8015 itself contains the requirement to mark specifications ‘TOLERANCING ISO 8015’ if they are to be interpreted according to its rules. As a result, this marking has become the way in which many organisations indicate that they are working to the ISO system, and is even now a requirement of BS 8888.

Arguably, specifications which are to be interpreted according to the ISO system should list all the other applicable ISO standards on the specification as well, or at least list them in a document referenced by the specification. For most organisations, this would be a lengthy list, including references to standards such as ISO 1101, ISO 2768, ISO 5458, and many others. Unsurprisingly, many organisations don’t bother.

The invocation principle was intended to avoid this difficulty, by introducing a rule which stated that if you are using one part of the ISO system, you are using all of it. This seems sensible to me. This approach does not require you use bits of the ISO system that you were not using previously, it just means that if you make use of any particular part of it, such as surface texture specifications, then all the relevant ISO standards apply. You don’t have to list them all, you just have to have some means of showing that one part of the ISO system applies, such as the ‘TOLERANCING ISO 8015’ indication.

The contentious stuff starts with a second part to this rule, which states that use of any ISO GPS symbol is sufficient to indicate that you are working to the whole ISO GPS system. In other words, you don't need to state ‘TOLERANCING ISO 8015’ or anything like that, you only need to use a geometrical tolerance, or a boxed dimension, or some other GPS symbol, and that makes it an ISO GPS document unless otherwise stated.

This is a REALLY BAD IDEA.

Reasons why:

1. In the UK, standards have a voluntary status. Their use cannot be imposed, and they work on an 'opt in' basis. This requirement would mean that many ISO standards would be imposed, quite possibly without the document owner being aware of this, unless they specifically 'opted out'. A requirement which is enforced by the absence of any alternative marking is liable to lead to confusion, misunderstanding, and resentment (and bring the system into disrepute).

2. ISO do not have ownership of all the symbols which are used in ISO GPS standards. Many symbols are shared with ASME, and many national standards organisations have used them in national standards which are still current. Some symbols are even used differently in other ISO standards

This requirement would mean that if someone forgot to put ‘ASME Y14.5’ on a drawing, it would then be regarded as an ISO GPS drawing, irrespective of the intention. It means that a sketch on the back of an envelope, which happened to include a dimension with a box around it, would suddenly be subject to the rules and requirements of an ISO GPS standard. It means that civil engineering or architectural drawings with tolerances might become subject to ISO GPS rules and requirements, without the relevant professions even being consulted.

3. As many of the symbols which ISO regards as ‘GPS symbols’ are either in the public domain, or widely used in different ways, in different contexts, an attempt to impose a requirement like this without consulting as widely as possible (other ISO technical committees, professional bodies, industry organisations, etc, etc,) is simply irresponsible.

4. A further consequence is that we would then need to introduce an exemption symbol or marking, such as ‘NOT AN ISO GPS SPECIFICATION’ for cases where it didn’t apply, at which point it is starting to get a bit silly.

5. What happens in the case of a nation which is not a member of ISO? What happens if ASME introduce a rule saying 'in the absence of any other marking, a technical specification is to be regarded as an ASME Y14.5 specification'?

The imposition of such a requirement would benefit no one, and simply lead to confusion, and quite possibly to litigation. ANSI have made their objections well known within ISO, but a number of people from other national bodies seem determined to force this through. I'm not clear on their motivation, but at least in part it seems to stem from a fear of 'Americanisation', and a desire to give ISO a higher status as the 'ultimate default'. These motivations may be sincere, but they are misguided. Industry will not benefit from this, and it will actually lead to the diminishment of the reputation of ISO standards if it goes through.

Prague in September

2010-10-30T01:23:00.000-07:00

Painfully overdue for a post here, so here is a quick up-date, to be followed by something more detailed in due course.

The latest TC213 conference met in Prague, capital of the Czech Republic, early in September.

Prague is a rather beautiful city. The old town has many famous landmarks, and it is clearly popular with tourists. The place was absolutely heaving, with large gaggles of people following tour guides wherever you went. Most of these groups were equipped with ear pieces, so they could hear the tour guide above the general din. Most of them also seemed to be following the lead of the guide in singing 'Good King Wenceslas', with varying degrees of tunefulness, as they marched around.

Tributes to Franz Kafka are also to be found throughout the city, such as the statue of The Man Who Wasn't There (see left).

I like the name of this bar as well (see below).

This was a very brief visit on my part. I flew in on Wednesday evening, chaired a meeting on Thursday, and flew out again on Friday.

The hot topic of debate was the 'invocation principle' which has been proposed for a revised draft of ISO 8015. Quite what this is, I will explain in the next blog post. The American delegation is outraged by this, and circulated a letter listing their objections prior to this series of meetings. Some other nations are strongly in favour, and one German delegate in particular has been mounting a charm offensive to cultivate support. The UK delegation is strongly opposed to this new principle, supporting both the American objections, and a number of our own. Many national representatives are remarkably ambivalent over the whole issue, considering its potentially far reaching effects. As I say, more on this to follow ...

New Courses

2010-08-07T04:58:00.000-07:00

It has been a busy summer so far.

We have developed and piloted a new Stress Analysis course, introducing the basic principles of stress analysis for calculations with calculators and spreadsheets. The idea has been to give engineers and designers the tools to carry out basic calculations for stress, strain and deflection in fairly straight-forward structures. This is really covering a lot of the same ground that engineering students cover at degree level, but compressed into three days, with a strong emphasis on practical application.

We had hoped to compress this into a two-day course, but that proved overambitious. We will be trialing the latest version of the course with the client who requested it within the next few weeks. Once all the creases have been ironed out, we will be publicising this with the other courses on our main web site.

When running the geometrical tolerancing course for one of our main aerospace clients, we frequently get questions and feedback comments about datums and tolerances applied to assemblies. There is not time to cover this adequately in the standard course, so we have proposed working with the client in questions to develop an advanced, follow-on geometrical tolerancing course. This new, advanced course would look in particular at assembly datum structures and assembly-level tolerances. If any other organisations out there (particularly aircraft manufacturers) would be interested in collaborating with us on the development of such a course, please get in touch.

First NPL GD&T course

2010-06-20T11:08:00.000-07:00

The first NPL GD&T course was held in the splendid setting of Bushy House in Teddington, where the National Physical Laboratory began over a hundred years ago. This is not far from Heathrow Airport, but you would never know it. Surrounded by the extensive grounds of Bushy Park, including cricket pitches, orchards and deer parks, we felt a bit like extras on a Jane Austin movie set.

This was one of the views from the museum room where the course was held. There are a herd of deer out there somewhere, but you can't see them in this picture.

The museum room itself was full of old bits of measuring equipment mapping some of the history of NPL since 1900, although some of the equipment looked older.

We had a great mix of people on the course, including three from Scotland, three from Ireland, and one from the Isle of Wight. They represented an equally diverse range of industries, including aerospace, boat building and medical equipment.

Feedback from the course has been highly positive, and we hope to run the next one in August or September.

Geometrical Tolerancing courses enter the NPL Training Framework

2010-05-06T02:03:00.000-07:00

Two of our Geometrical Tolerancing courses are now available as accredited training courses through the National Physical Laboratory Training Framework.

Geometrical Tolerancing to BS 8888 and ISO Standards.

Geometric Dimensioning & Tolerancing to ASME Y14.5.

We are running the first of these as an open 3 day course at the National Physical Laboratory on 25th, 26th and 27th May.

As far as I know, this is the first time that accredited Geometrical Tolerancing courses have been available in the UK. The courses are accredited by the National Physical Laboratory and validated by The National Skills Academy for Manufacturing. Delegates who successfully complete the course receive a numbered certificate, registered with NPL Training, which also carries the National Skills Academy logo.
The same courses are also still available from us in non-accredited form (which means that they cost less). I have no idea yet how much interest there will be in accredited training in these subjects, but the response to the public course we are running at NPL later this month has been very good, and the course is almost full.

Email me if you want further details about these courses, or know anyone else who might be interested.

Gadgets

2010-04-28T02:56:00.000-07:00

This month I took delivery of a new HTC Desire mobile phone. What a brilliant little device! The Google Sky Map is a fantastic app.

Also stumbled across a web site for some of the most amazing time pieces you are likely to see: check out the 'Horological Machines' at http://www.mbandf.com./ Will someone get me one for Christmas please.

NPL Training Courses

2010-03-16T04:39:00.000-07:00

The National Physical Laboratory (NPL) is the UK's National Measurement Insitute. They are responsible for measurement standards in the UK, and are a leading centre for scientific research. NPL provide guidance on good practice, wide ranging resources for education, along with commercial training and consultancy services.

The NPL Training Framework consists of a matrix of measurement-related training programmes. The framework has been developed in partnership with industry with the following objectives:

to develop core skills and competencies in practitioners
to raise the level of technical knowledge
to promote and instil good practice
to foster a questioning and planning culture

The NPL training programmes are accredited by NPL, validated by The National Skills Academy for Manufacturing, and delivered only by NPL Accredited Training Providers.

Iain Macleod Associates became an NPL Accredited Training Provider last year for the courses in dimensional measurement. These courses teach the fundamental principles of metrology for engineers, inspection and QA people.

Courses which teach people how to inspect engineering components obviously have a natural fit with courses which teach people how to specify engineering components, and make a logical extension to our training portfolio. This means that we can now offer a consistent range of training courses across the spectrum of design, manufacture and inspection.

Click here for a flyer describing these courses in more detail.

Only in America ...

2010-02-25T08:30:00.001-08:00

Frosty in Vienna

2010-02-23T03:39:00.000-08:00

Recently returned from the ISO TC213 conference in Vienna. Vienna was beautiful, but bloody cold.

Some useful progress was made in some of the working groups.

WG17, which I chair, has been given the task of updating a document which has the vaguely threatening title of 'ISO/TR 14638 - GPS Masterplan'. This document maps out the structure of the entire ISO GPS system, and describes how the different standards relate to each other.

The document has not been touched for about 15 years, and is very hard to understand, so there is quite a lot of work to do. In fact, most of the 'up-date' will probably involve redrafting large sections of the text just to try and make it comprehensible.

In the previous TC213 series of meetings in San Antonio, a new study group was set up to map out the differences between the ISO GPS system, and the American ASME Y14.5 standard. The study group is jointly led by Archie Anderson of the USA, who oversaw the development of Y14.5 for many years, and Renald Vincent of France, who has played a major role in the development of GPS over recent years.

Meeting again in Vienna, we have now mapped out a structure for the comparison, and can start to fill in some of the detail. I think that this could potentially be a very useful study, as the differences are not always well understood, and organisations in many areas of industry are having to work with both systems.

WG 18, which deals with the geometrical tolerancing standards, was a much patchier affair. Too many new options and possibilities being introduced, and not enough progress on sorting out what we already have.

Encouraging signs for 2010

2010-01-23T01:16:00.000-08:00

It is a long time since I posted anything here. Happy New Year to anyone who reads this.

We seemed to turn an economic corner around Autumn last year. There was a noticeable upturn in the number of enquiries I was receiving in November, and then things started to get very busy indeed in December. The level of work has continued into this year - I've been away training for most of the last two weeks, and have a reasonable number of courses booked in for the next couple of months.

In the last few days, I've even had an enquiry from a company in the automotive supply chain, the sector which was probably hardest hit of all in the downturn, so all around there seem to be positive signs of recovery.

During the quieter bits of 2009, I became a licenced deliverer of some of the metrology courses offered by the National Physical Laboratory (NPL), and I intend to expand that area of activity in 2010. These courses teach the fundamentals of measurement and inspection, and are a perfect fit with the geometrical tolerancing training that I offer already. It means that we should be able to provide a seamless, and fully consistant, series of training programmes across the disciplines of design, manufacture and inspection.

One area of particular interest is Large Volume Metrology, where laser scanners or trackers are used to scan large components or assemblies to very high levels of accuracy. The aerospace insdustry is starting to use this technology extensively, and it also has applications in other industries.

New Years Resolution - to try and keep this blog updated more frequently.

Three days in San Antonio

2009-09-19T07:36:00.000-07:00

The latest ISO TC213 conference was held in San Antonio, Texas. Other commitments meant that I was only able to fly in for three days of the conference, which lasted about 10 days altogether.

I flew from Manchester via Atlanta, a most efficient airport, where it took no more than about 30 minutes to pass through immigration, collect luggage, redeposit luggage, pass through security and make my way to the correct terminal and gate for the next leg.

I arrived in San Antonio, which had been enduring weeks of heat wave recently, to find it raining. Their first proper rain for 18 months, timed to greet a visitor from Manchester! It rained on each of the following three days as well.

Most of the trip was spent inside the Holiday Inn, where all the delegates were staying, and all the meetings were being held. I was in meetings from 9:00am to 8:00pm on the first day, and 9:00am to 6:00pm the second day, so I did not see a lot besides the inside of the hotel until day 3.

San Antonio itself is smaller than I expected, as American cities often seem to be. I expect them all to be huge, and most of them aren't. According to Wikipedia, its population is around 2 million (smaller than Manchester), and it is still the seventh largest city in the USA. Rain showers each morning cut the humidity to comfortable levels, and left it pleasantly warm and even fresh while I was there.

We saw the Alamo, of course, which is close to the centre of the city.

Also in the heart of the city is Riverwalk: one storey below street level, there are walkways along either side of the San Antonio river, where there are clustered a vibrant collection of bars, shops and restaurants. We strolled along here each evening to find somewhere to eat, and always ate well.

My flying visit was quickly over, and then it was back to Manchester (which had enjoyed some of its sunniest weather in my absence).

The next TC213 conference will be in Vienna in 2010, which I will look forward to. I just hope that the ISO habit of scheduling meetings to run all evening as well as all day will still leave a little time to see the city.

Next BS 8888 now scheduled for 2011

2009-08-09T13:33:00.000-07:00

Been very remiss with postings recently. Somewhat shocked to see the last one was on 1st July! My only excuse is that I was away for half of July, and spent the other half doing some major updates to training course material (lots and lots of new diagrams, which always take ages to get right).

Anyway, we had a meeting last week of the BSI committee looking after BS 8888 with a view to getting preparation of the next revision (then scheduled for October 2010) underway.

We had a useful review of the current edition, and are making plans to restructure the content (to make the information more accessible), add more diagrams and illustrations, and to cull the annexes, which now make up almost 75% of the document. These annexes have been added over a period of time, with intention of providing additional explanation and useful background information, but they are getting a bit out of hand. Some will stay, and may even be extended, but some will be incorporated into the main body of the standard, and some are no longer necessary and can be removed altogether.

We then turned our attention to a number of forthcoming ISO standards and amendments, which I have already mentioned on previous posts. These are bringing through some significant changes and additions to the system of technical specification. The justification for the next revision of BS 8888 lies in providing coverage of the changes and developments that these new standards and amendments will bring.

- ISO 1101 amendment 1 is bringing in the additional annotation elements required for fully annotating 3D CAD models.

- ISO 1101 amendment 2 is introducing additional symbols, bringing in some new, and rather technical functionality to geometrical tolerancing.

- ISO 5459 is a complete overhaul of the definitions and rules for datums.

- ISO 14405 is a new standard on linear sizes, which will replace ISO 8015.

In each case, we reviewed the timetable for the new document - how many comment, discussion, amendment and voting stages each has still to go through, and the likely timescale for that to take place. Our conclusion was that there is a faint chance of ISO 1101 amendment 1 being ready for inclusion in a 2010 revision of BS 8888, but that none of the other will see the light of day before 2011 at the earliest.

While we could bring out a 2010 revision of BS 8888 with tweaks, adjustments and improvements, there is no technical justification for a revision of the standard until these new technical changes and developments can be included. I am pleased to say that we have decided to delay a revision of BS 8888 provisionally to 2011. Pleased, because I have wanted all along to make BS 8888 a more stable standard that changes less frequently.

Our decision has also been influenced by the fact that some of these future developments are still fairly contentious, and have a rocky road ahead of them before they are finalised. In several cases, the new standards are introducing new possibilities and symbology to address very specialized and rarefied applications, and they run the constant risk of making the whole system horribly complicated in order to address issues which are of largely academic interest.

The UK representatives on the ISO committees have always sought to avoid unnecessary complexity, and to take a pragmatic, working engineer's approach to these new developments, but we don't always manage to get our own way. Amid the complexities, however, there is also much genuinely useful work taking place. Some of these new standards are now clearly defining rules and principles that have previously often been implied rather than stated, and rarely properly understood. Our challenge is to introduce these in a way that is practical and useable for industry at large.

In just over 4 weeks I shall be going to Texas for the next ISO TC213 conference (having finally managed to find some affordable flights), and will report back on how things develop there.

Catching up

2009-07-01T12:59:00.000-07:00

I was away training last week. The course went very well indeed, but I'm always a bit drained afterwards. Friday night was then spent at a charity ball/auction to raise funds for my childrens' school - a terrific night out at The Lowry in Manchester, but a very late finish.

Saturday was when Friday night caught up with me. Sunday was a fund-raising sponsored walk (the childrens' school again - who schedules this stuff?) with me trying to catch up with the kids. And this week has been mainly catching up with admin so far.

I have a meeting coming up next week at BSI for TDW/4/6, the committee dealing with education. We have been slowly working towards a fully accredited training scheme in Geometrical Product Specification for some time now. The IED are going to be the accreditation body, but we still have a long way to go in sorting out the details of how the process will work, how it will be funded etc. I need to catch up with some outstanding actions on structuring the curriculum.

In TDW/4/6 we have learnt a great deal from the National Physics Laboratory (NPL) who have had a system of accredited training for metrologists in place for sometime now. When I catch up with everything else, I'm planning to become a deliverer of the NPL training. It is a near-perfect fit with the geometrical tolerancing training I'm providing now.

Something more technical next time ...

ISO 1101 amendment 1

2009-06-22T15:02:00.000-07:00

ISO 1101 is the principle ISO standard for geometrical tolerancing. It was last revised in 2004, just five years ago, but there are already a number of amendments queuing up to be incorporated into it.

The first of these, Amendment 1, is concerned with 3D annotation, and is going through the final stages of approval prior to publication. It is likely to come into effect some time in the next 12 months.

What is '3D annotation'?

It is established practice in most industries to use a 3D CAD model as an essential part of a component specification. The 3D model represents the 'nominal' geometry of the part, and as many manufacturing operations, and some inspection operations, can be driven directly from this 3D model, there is no longer a necessity to duplicate this data with dimensions on a 2D engineering drawing.

This has paved the way for the 'minimum content drawing' approach that is now widespread. The 2D drawing is used to convey information about datums, tolerances, surface finish and sometimes inspection requirements, but no longer needs to define the fundamental geometry of the part.

The next stage in the evolution of this process will be to apply the information about datums, tolerances etc directly to the 3D model, eliminating the requirement for a 2D drawing at all. This is what is meant by '3D annotation'.

Eliminating 2D drawings does not really become a practical proposition until everyone involved in the specification, manufacture and inspection of the component can work fully in 3D. For most of industry, that prospect is a distant one, so 2D drawings are going to be around for many year yet.

However, CAD software is increasingly providing the facilities to apply all specification requirements directly to the 3D model, and some manufacturing organisations are starting to work in this way.

The CAD software is currently a little ahead of the standards in this respect. While most 3D annotation requirements can be met quite happily by applying the 2D annotation elements in a 3D environment, there are some situations where this is not sufficient. Some specification elements depend on the positioning of a geometrical tolerance within a drawing view to convey part of the requirement. Working in 3D, we no longer have drawing views to position or orientate the geometrical tolerance, so other means have to be found to convey that information.

Amendment 1 provides some illustrations to indicate how a geomtrical tolerance requirement can be indicated in a 3D specification as well as in a 2D specification. More importantly, the amendment introduces some new annotation elements to enable all geometrical tolerance requirements to be fully specified in 3D. Symbols have been introduces to define 'intersection planes' and 'orientation planes', which can be used to define the location or orientation of a tolerance requirement relative to the 3D model.

The amendment also ties up one or two other loose ends. It will indicate how the 'all around' symbol can be used in 3D (although in my view there is no need to use it in 3D at all). There is also a new symbol to help make it clear when a derived feature, rather than a surface, is being used as a datum feature.

Finally, there will now be the facility to define offset tolerance zones. This last was something of a disappointment for those of us who argued in favour of adopting the American (Y14.5) symbology in the interests of simplicity, clarity and universal harmony. The ISO approach will be different from the Y14.5 approach, but at least we managed to avoid using the same symbol as the Americans', but with a different meaning (a very real possibility at one stage). Sometimes, these tiny, common-sense achievements rank as great victories when developing international standards.

BS 8888:2010

2009-06-20T00:32:00.000-07:00

We are now starting to plan the next revision of BS 8888, which is due out in October 2010.

BS 8888 is currently up-dated every two years. I think this is far too frequent, and in principle, I would like the standard to be much more stable, and only up-dated every four or five years. This has been one of my objectives since I took over the chair of TDW/4/8, which is responsible for BS 8888.

However, BS 8888 acts as an interface to the ISO system of standards, and has to be kept up-to-date with changes in the ISO system, and this is what fundamentally drives the revision cycle.

In recent years, there have been a lot of developments within the ISO standards, and BS 8888 has had to change frequently to keep abreast of these changes. Right now, there are some more major changes in the pipeline, and a further revision of BS 8888 for 2010 is unavoidable.

So what changes are on the way? Four major ones at least:-

1. Amendment 1 to ISO 1101 (the main ISO standard for geometrical tolerancing).

This mainly deals with 3D annotation.

2. Amendment 2 to ISO 1101.

This introduces some new symbols, and also extends the system in several ways. For instance, some of the filtration options which can be used with surface texture specifications will be available for form tolerances.

3. ISO 5459

This is a major up-date of the datum standard, which is long over-due.

4. ISO 14405.

This is a new standard for linear sizes. It will replace ISO 8015, and provide a more comprehensive range of options for how we define sizes of features.

I'll give further details about some of these developments in future posts.

Geometrical Tolerancing, standards and related stuff

2009-06-18T01:41:00.000-07:00

Does the world really need another blog?

I'm about to find out. This is my first experiment with blogging, and it really is an experiment. If it generates some interest and dialogue, then I will keep it going. If it doesn't, then I'll quietly close it down at some point.

I run my own business. I provide training and consultancy in geometrical tolerancing, engineering drawing, and related issues. I am also involved in the development of the standards which govern this field, through technical committees at BSI and ISO.

The people I work for are mainly in the aerospace and defence sectors, companies like Airbus, BAE Systems, and MBDA.

I also work for organisation like Toyota, Siemens, Thales, several in the Oil and Gas sector, and numerous SMEs across a wide range of industries. My clients include some of the Formula 1 teams, and scientific establishments like the Rutherford Appleton Laboratory - all of them fascinating in different ways.

I will be recording here, on an occasional basis, my thoughts and experiences on running a business, on working with tolerances and specifications, and on developing the British and ISO standards.

This is not going to be a free help-line on tolerancing issues, although there may well be discussion about the standards like BS 8888, ISO 1101, ISO 5459, etc. In part, I hope that this blog will throw some light on how these standards are developed.