Technical Talk

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Renegadenemo
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Re: Technical Talk

Post by Renegadenemo » Sat Jul 22, 2017 3:43 pm

Ah, but the BA standard isn't British. It's Swiss or Swedish or some such, where people can't count to twelve.
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thunderer
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Re: Technical Talk

Post by thunderer » Mon Oct 02, 2017 3:06 am

Correct me if I am wrong, but I always understood, and was always taught that, BA stood for "British-Association".

Was I misled?

Editied because I typed "British-Armstrong" in place of "British Association".
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Renegadenemo
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Re: Technical Talk

Post by Renegadenemo » Mon Oct 02, 2017 2:13 pm

Correct me if I am wrong, but I always understood, and was always taught that, BA stood for "British-Association".
You're right enough but we nicked it from the Swiss watchmakers - at least that's what one of my lecturers told me many years ago.
I'm only a plumber from Cannock...

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mark-f

Re: Technical Talk

Post by mark-f » Mon Oct 02, 2017 2:47 pm

British Association screw threads, or BA screw threads, are a largely obsolete set of small screw threads, the largest being 0BA at 6 mm diameter. They were, and to some extent still are, used for miniature instruments and modelling.

They are unusual in that they were probably the most "scientific" design of screw, starting with 0BA at 6.0mm diameter and 1.0mm pitch and progressing in a geometric sequence where each larger number was 0.9 times the pitch of the last size. They then spoiled this by rounding to 2 significant figures in metric and then converting to inches and rounding to the thousandth of an inch. This anticipated worldwide metrication by about a century. The design was first proposed by the British Association in 1884[1][2] with a thread angle and depth based on the Swiss Thury thread,[3] it was adopted by the Association in 1903.

The Thury thread was different in that it went both positive and negative all the way up to a size of -20 which was 75.2mm diameter by 8.23mm pitch. The Thury numbers were rounded to three significant figures. The Thury thread form had the crests rounded at 1/6p and the roots rounded at 1/5p so the thread angle was close to 47.5 degrees but not exactly. This was simplified in the BA thread definition by defining the thread angle to be 47.5 degrees exactly and the thread form to be symmetrical with a depth of 0.6p.

The British Standards Institution recommends the use of BA sizes in place of the smaller British Standard Whitworth (BSW) and British Standard Fine (BSF) thread screws (those below 1/4").[4]:4 Generally, the 0BA size was dropped in place of 7/32" BSF in assemblies that included larger fasteners, however, in smaller equipment that was primarily electronic/electrical the 0BA size would typically be used in place of the BSF or BSW screw where it was the largest size required.

BA threads are still used in some precision instruments, such as optics and moving-coil meters, relays etc. A 2BA thread is used to connect the head of a dart to its shaft — as such, it is one of the few common uses of this thread in North America.

2BA threads are commonly found in the old imperial BESA (British Engineering Standards Association) conduit boxes in the UK which are still in use (but not installed) today.

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Re: Technical Talk

Post by Renegadenemo » Thu Oct 12, 2017 12:57 am

Absolutely cracking doco here for anyone interested in metal shaping.

https://www.youtube.com/watch?v=b4haVtIP2M8
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rob565uk
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Re: Technical Talk

Post by rob565uk » Thu Oct 12, 2017 7:10 am

Renegadenemo wrote:
Thu Oct 12, 2017 12:57 am
Absolutely cracking doco here for anyone interested in metal shaping.

https://www.youtube.com/watch?v=b4haVtIP2M8
It wont load Bill - looks like the link has been closed down

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Re: Technical Talk

Post by Renegadenemo » Thu Oct 12, 2017 8:39 am

Try this one then

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Re: Technical Talk

Post by rob565uk » Thu Oct 12, 2017 7:20 pm

That works and is absolutely fascinating

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Re: Technical Talk

Post by Renegadenemo » Sun Nov 05, 2017 1:54 am

Amazing day in the workshop today and another major milestone reached. The second, 20ft long floor panel went on without a hitch and with about 5000 rivets. Eleven people and six hours of non-stop graft following several weeks of preparation and Bluebird is watertight once again for the first time in almost 51 years.
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midlife
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Re: Technical Talk

Post by midlife » Sun Nov 05, 2017 1:57 am

Awesome news Bill, congratulations to all involved [.][.][.]
Cheers
Wayne


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