metrication

The simple answer is a set of "Metrinch" sockets and spanners and throw away all the others. Metrinch, and a couple of other brands grip the hex head on the flats not the corners and so are very tolerant of sizes and are the best for damaged hex heads. My son has a set I bought him for his 18th and I have used them more than him.

Ahh Yes,BSW. i still have a Siddy socket set and some ring spanners in BSW. i use 7/16-1/2 double ringy almost everyday. the 7/16 can be substituted with an 18mm and the best fit for the 1/2 is a large spark plug socket (13/16?) as they cant be bought in BSW anymore. all of my guys use metric but old habits and spanners die hard with me.

Just an aside,

AF, I was brought up believing it to be American Fine, however, Ive heard it also referred to as Across the Flat.

Which is it ?


Cheers.....Lionel.

Bear a thought for the mixture of numbers written tyre sidewalls ?

This was written for a different purpose, but may be of interest !

Nuts n bolts

Once upon a time ….

Why won’t the nut fit the bolt?

In the early days of nuts and bolts, when machining was pretty imprecise, the bolts weren’t too hard to make but making the internal thread for the nuts was a real problem. Initially, a number of nuts would be made until one fitted the bolt. That particular nut then stayed with that particular bolt. As precision improved and the yields got better, different manufacturers adopted different “standards” so as to ensure continuing return business. Nuts and bolts were big business during the industrial revolution which had its core in Britain, and the lack of standardization was a serious impediment.

In the mid 1800’s, Joseph Whitworth, a tool maker, introduced his revolutionary thread system to the Institute of Civil Engineers. His system defined the shape of the threads (55degree with radiused peak and valley), the pitch (threads per inch as a function of shank diameter) and sizes expressed as the diameter of the material from which the thread was cut. The size of the hexagonal head was defined by the available hex rod sizes from which the early bolts and nuts were made. Thus a ½” Whitworth wrench actually fits a hex bar which is the size bigger than ½” round and which itself isn’t ½” anywhere.

Three British families of threads were developed; a miniature series known as BA or British Association, a coarse thread series known as BSW or British Standard Whitworth and a fine thread series known as BSF or British Standard Fine. As one would expect, a ¼” BSW was made from ¼” diameter rod, a ½” BSW from ½” rod and so on. Pretty simple so far. BA however went the other way – the diameter of the rod is dictated by the pitch, and the smaller the bolt the larger the BA size number. A 0BA bolt is actually 6mm in diameter with a 1mm thread pitch, and a 6BA bolt is much smaller – remember, this is a historic British standard! Although a great leap forward, the British standards still offered a great deal of confusion.

BSW and BSF remained the standards for nuts and bolts used in British machinery and vehicles until the mid 1900’s and were still in common use until the 1970’s.

Meanwhile the Americans had developed their own standards, again 3 sets, under the auspices of the Society of Automotive Engineers (SAE).
They adopted the
i) The SAE number series, equivalent to the British BA series
ii) SAE UNC or Unified National Coarse equivalent to the BSW
iii) and SAE UNF Unified National Fine, equivalent to BSF.

A significant departure from the British standards was the adoption of a 60 degrees thread angle rather than the Whitworth 55 degrees. The Americans also dispensed with Whitworth’s radiused thread shape which required complex tooling. Some SAE nuts will almost go onto some Whitworth bolts, but only almost! The American Standard or SAE sizes relate to the distance across the flats of the head, not the diameter of the stock from which the thread was made.

In 1949, after the Second World War, these SAE standards became the Unified Thread System.

The business of making threads was hardly new. Rifling in gun barrels goes back to the early 1500’s, though not in Britain. In America it was used during the Civil War. Rifling for larger artillery lagged way behind, so that a competent sharp shooter with a rifle could take out an artillery crew without much risk from the big gun! Whitworth developed the necessary tooling to provide rifling for British artillery pieces. This work for the military influenced the development of the British standards for nuts and bolts.

It was the Second World War, which finally brought to a climax the disastrous lack of standardization. America’s industrial strength supplemented British industrial efforts in opposing Germany and the lack of standardized tooling and sizing proved massively costly. There can be no doubt that lack of standardisation of something so simple as nuts and bolts had a very significant impact on the war.

Of course, that’s all history now. The British adopted the American standards, and everyone lived happily ever after……... until we went metric that is…………

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And then there is the Land Rover special size! Ran around for a long time to find the thread pattern for an old series I welsh plug thread - had to get a tap made in the end.

Kind regards

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Nudie,

All passenger cars, be they Japanese, Korean or Calathumpian contain at least two BSW treads.

They are for the child restraint points, 5/16 BSW (also known as UNC). It apparently has something to do with America setting a world standard for mounting of child restraints.

Jim.

John & Val are pretty well spot on with their info.
however most common BSW and UNC nuts and bolts are interchangeable except for 1/2". BSW has 13 thread per inch whilst UNC has only 12.
If you need spanners for BSW nuts and bolts them the appropriate A/F (Across Flats) spanners will suit. But remember the A/F size will be somewhat larger than the bolt or nut thread size.
Point of Interest. BA threads were developed primarily for use by the electrical industry.
Probably all major vehicle manufactures world wide have now gone metric including in the USA. The same goes for the Aircraft industry.
For some unknown (To me at least) Carpenters in Australia still use BSW nuts and bolts. This being the reason (or vica vera) that hardware stores only carry BSW and not Metric. Bloody nuisance that is.
Historic Fact: The US congress passed legislation in 1886 that metric weights and measures were to be the US standard. Unfortunately it wasn't made mandatory like in Australia, so industry and consumers just kept using the system that they were comfortable with. This leave the US as the only major country still using imperial, not Briitsh Imperial, but one of their own making.
In the UK however they have moved to metric for engineering (Including the thread system) but still maintain miles, pints, horsepower etc. Weird lot those Poms. As an engineer I was lucky to be schooled in British Imperial, then work for a number of years for a US company using US Imperial. I was still working as and Engineer when the mandatory change to metric toook place. So for my last 20 or more years in an industry (Can Making/ Carpet weaving & Food processing) I was, because of old machinery within these industries, made in many different countries, required to work with all three systems. Could be very interesting at times and downright confusing at others.
ozjohn.

In a similar vein, on Top Gear I was initially bemused by, and then increasingly annoyed by their use of quaint archaic terms like foot pounds (torque), pounds of thrust (for jet engines), horsepower (clydesdale or quarter horse), miles per hour (or leagues per day?).

I believe some of NASA's cockups may have been due to using anachronistic and incompatible units for their rockets (how many pounds of rocket fuel does it take to fly to the moon and back?)

I say to the yanks and the poms: "Wake up, get with the rest of the world, and let go of your xenophobic, imperialistic notions and go metric."

We will never become fully metric in engineering.
In the fitting & turning & the toolmaking trades these odd old fashioned threads are going to be here for ages. Possibly even centuries.
The reason is that a lot of machinery made in the early 20th & late 19th century is still in use & still requires maintenance. New parts have to be made to fit the existing machine. That's what a fitter & turner does.
Sugar mills are a classic case. They work in dozens of thread profiles. Metric Coarse, Metric fine, UNC, UNF, BSW, BSF,BSPT, BSPP, Brass (all 26 tpi), Square & the list goes on forever. Pages & pages & pages in engineering handbooks of tables of thread profiles. The list would have grown from what is in my old handbooks because of new materials with different mechanical properties.
Then of course you get into fitted threads & the tolerances on them. Depending on the application a thread might need to have a certain class of fit. The tables & have specific dimensions to achieve specific outcomes.
AS for Bunnings, they are the K-Mart of hardware. OK if you want some cheap stuff, but not if you want something specific.

Hey MN 1
Your best bet for bsw tools these days, is try cash converters or the markets.
And a second hand tool store i you have any in your area.
Deceased estate and garage sale.
And i don't buy any thing if possible that has not metric cars included.
Or get a good selection of shifters.LOL

Rob

This is getting a bit off topic, but helps to sum up the confusion in this area.


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There are more than a few placws to buy whitworth spanners you just have to look and be prepared to pay.

Here is One -

http://www.whitworthspanners.com/category1?PHPSESSID=70587dcec550c1e502e512dddad7eaef

and another with a conversion table at bottom of page

http://www.baconsdozen.co.uk/tools/whitworth.htm