19 replies to this topic

[m9a3r5i7o2n]

I have just this day recieved a 30 page document about the Old 1917-1918 Sunbeam "ARAB" V-8 718 cu. in. engine. Many threads have call out outs such as 1/4"N.26 A.G.S. 116B or 1" x 1/16" S.P.8 A.G.S.

Looked in Machinerys Handbook and searched the Internet with no results. Any Ideas.

Yours, M.L. Anderson

[AyePirate]

Try the Nostalgia Forum. There are some regulars there that are pretty heavily involved in Historic Racing and restorations.

http://forums.autosp...p?s=&forumid=10

[Vegetableman]

Hi,those are aircraft bolt specs. Aircraft General Stores. They could consist of anything from nuts and bolts to valve assemblies. They were meant to help standardise use of components. These are obsolete now obviously.

That is my understanding anyway.

[Joe Bosworth]

m9a

I think that Vegman has gotten you part of the way through your querie.

I have never physically worked on a vehicle of 1917-18 vintage but have spannered a 1934 Leman Aston Martin.

With almost total certainty you car is fully fitted with Whitworth fittings. Whits are well documented in Machineries Handbook if you have an old enough version. They really are devilish devices and IMHO probably held back British engineering by years.

Regards

[D-Type]

Screw threads are a minefield. My Dictionary of Science and Technology gives:

British Standard Fine (BSF) Thread: a screw thread of Whitworth profile, but of finer pitch for a given diameter; largely used in automobile work

British Standard (Whitworth (BSW) thread: The pre-metric British screw thread, still widely used in the US, having a profile angle of 55 degrees and a radius at root and crest of 0.1373 x pitch; 1/6 of the thread cut off. The thread is standardised with respect of the bar on which it is cut.

Before going metric the UK switched to "unified" threads for which the dictionary says:
Unified screw thread: A screw thread form adopted by Canada, UK and US. It combines features of the US Standard screw thread and the British Standard Whitworth screw thread. Of 60 degree angle, the thread has radiused roots and crests while the crests of the nuts are flat.

It goes on to say that the US Standard (USS) thread, also known as a Sellers Thread, has a 60 degree angle and do metric threads.

The British Association (BA) thread uses a 47 1/2 degree angle and was largely used for instrument and electricalwork. Designated by numbers 0 to 25, eg "0 BA".

If I remember correctly, in terms of spanners, the UNC and UNF threaded bolts have spanners defined in terms of the measurement across the flats (AF) while the Whitworth bolts have spanners defined in terms of the shank. So a 1" Whitworth bolt needs a spanner of about 1.73" AF. AF spanners don't quite fit Whitworth bolts and you end up with rounded corners and skinned knuckles.

[Allan Lupton]

Quote

Originally posted by D-Type

If I remember correctly, in terms of spanners, the UNC and UNF threaded bolts have spanners defined in terms of the measurement across the flats (AF) while the Whitworth bolts have spanners defined in terms of the shank. So a 1" Whitworth bolt needs a spanner of about 1.73" AF. AF spanners don't quite fit Whitworth bolts and you end up with rounded corners and skinned knuckles.

What most of us have on the workshop/garage wall is a chart of BSF, A/F and metric spanner sizes in order of jaw size so that even if we haven't the right spanner we know which is the next one that will almost fit.

A trap for the unwary is that in the original standard BSF hexagons were one size down from BSW, hence the spanners being marked with two sizes. Modern BSW nuts and bolts seem to use BSF hexagons.

[D-Type]

Quote

Originally posted by Allan Lupton


What most of us have on the workshop/garage wall is a chart of BSF, A/F and metric spanner sizes in order of jaw size so that even if we haven't the right spanner we know which is the next one that will almost fit.

A trap for the unwary is that in the original standard BSF hexagons were one size down from BSW, hence the spanners being marked with two sizes. Modern BSW nuts and bolts seem to use BSF hexagons.

Some of us are obviously more organised than others. I don't use them much nowadays so I have all my spanners in a tool box and use trial and error.

The most infuriating thing I have found is the mother-in-law's house electrics - the boxes (mostly) are threaded with metric threads so if I change a switch or anything I have to use the old screws no matter how rusted or mangled they may be rather than nice new shiny ones that fit my screwdriver.

[m9a3r5i7o2n]

You all have made a great deal of help and I will go there after I study it some more and make a more throrogh list but you all have been of help. With the information given I was able to decipher almost all of the A.G..S. material. Except for the Size and Thread of the Nuts since the engine seems to use only Studs everywhere there are no callouts for Bolts. Now to the other place mentioned. Thank you all!
Yours. M.L, Anderson

[Charles E Taylor]

AGS

Your project may be much older that the current AGS standard. Aircraft General Standard/Supply/Stores?

For small quantities of AGS Bolts please try http://www.lasaero.com/

A25 series have BA/BSF threads

A102 series have UNF/UNC threads.

Please see http://www.lasaero.com/article/a-a25


Good luck





Charlie

[Ray Bell]

Quote

Originally posted by D-Type
.....The British Association (BA) thread uses a 47 1/2 degree angle and was largely used for instrument and electricalwork. Designated by numbers 0 to 25, eg "0 BA".....

BA threads were also very common on bicycles, which led a lot of uninformed people to call them 'BSA' threads (for BSA cycles, which were known in various parts of the world in the fifties and sixties), and also in model making...

Colin Wear, builder of the Welsor cars, used to retail BA nuts, bolts and probably studs in a variety of sizes, ranging through microscopic and tiny to small, to model railway builders in Australia... and probably New Zealand.

[JtP1]

I cannot find my thread chart book at the moment, but here is a short resume of how the UK got into the thread mess we live/lived in.

The original Whitworth thread was created by Whitworth for the Enfield rifle works when he set it up to have a standard thread for the works and the British Army. BSW was one of the first standard threads ever created, if not the first. Later on a finer thread was created BSF. During WW1 the head sizes were moved up one bolt size to save metal, the steel used to make the bolts and nuts being of a much higher quality than that of the original Whitworth material. Thus a 5/16" BSW bolt recieved a 1/4" BSW head. Hence the spanner (this is a British thread discussion, but a wrench to the colonials) was double marked 1/4" BSW/ 5/16" BS.

By WW2, lots of military equipement was made in Britain and the USA, but with the local thread which caused lots of spare supply problems. For example, a RR Merlin was BS and the Packard version was US threadedand from that, a MK1 Lancaster had RR Merlins and a MK3 had Packard to make sure only the right threaded aircraft was sent to a squadron . So Unified National Fine and UNC were created as a standard thread between the 2 countries. This thread was then adopted in the US as Standard Automotive Engineering around 1948. The USA AN series of aeronautic bolts are SAE/ unified thread. In 1970 the UK then started to use metric as a standard thread, surely the only country that has changed its standard thread twice in 30years. An aside to this is that Land Rovers at one time came with UNF threads, but with BSW heads. I guess the British army had lots of BS spanners. Strangely BSW is still to be found in brass castings, I reckon it takes a lot of wearing out of a tap in brass.

The most unusual thread I ever heard of and still apparently in use is PG or Panzer Gauge. It is used to fit radio aeriel connections in tanks.

[Lee Nicolle]

And to confuse matters more Whitworth and UNC are the same thread per inch under 1/2" but a different pitch. So a BSW bolt will accept a UNC nut and vice versa but is tight one way and loose the other and strips very easily and does not give true tensions.And some sizes of metric course will almost accept NC nuts etc
These days a lot of hardware store garden type bolts are still whitworth, cars built in the 80s and 90s still had lots of UNC and UNF bolts in them. Sometimes and NC bolt with a metric head!And there is several metric threads too. Euro cars seem to have different TPI to jap and Aussie cars.
I wish you luck with something that old. If you have major strength threads that do not line up with modern threads possibly you could helicoil them and then use modern bolts which are generally of better quality anyway. BUT use good quality brand name bolts as some cheap bolts are rubbish. I think they are being made in India? but are either very elastic or too brittle and snap very easily.

[Allan Lupton]

Quote

Originally posted by Lee Nicolle
And to confuse matters more Whitworth and UNC are the same thread per inch under 1/2" but a different pitch.

Threads per inch and pitch are reciprocals: what you refer to was covered above where it was noted that BSF/BSW use a 55 degree thread angle and UNF/UNC use 60

Then there is the cycle thread set at 26 t.p.i for all diameters and the BSP (pipe) threads that were mostly used for domestic plumbing but appear on cars' oil pipe connections.

[h4887]

Quote

Originally posted by JtP1

The most unusual thread I ever heard of and still apparently in use is PG or Panzer Gauge. It is used to fit radio aeriel connections in tanks.

I've always been rather fond of the German Bottle Closure Thread. But then Sidders' 'Guide to World Screw Threads' is never far from my bedside table...

[m9a3r5i7o2n]

Well, it's no wonder that the keeping of old cars and aircraft is so expensive with all the differences and practically unobtainable bolts, nuts washers and other items!

I have found what I'm sure is the answer: the threads are the old British Standard Whitworth, (BSW) 55 degrees and range all the way from 1/16" to 1” in a chart at British Tool & Fasteners and these charts also include BA, BSC, BSF, BSP, BSTP, BSW, CEI, UNC, UNF, and ME.

I wish to thank you all for your most welcome help, Yours M.L. Anderson

http://www.britishfa...hreads/bsw.html

[D-Type]

I must share this from the website that Marion has identified:

Quote

The first thing any fledgling British car restorer learns is that his (or her) car has "Whitworth bolts." They think this is interesting, buy a set of "Whitworth spanners," discover these spanners fit their bolts, and believe they now know everything they need to know about British fasteners. Unfortunately, at this point they know only enough to make themselves dangerous. Instead, what they should have said to themselves is "Oh my God, what other weird and incomprehensible things have they done to the fasteners on my machine?"

[Allan Lupton]

Oh, and on a lighter note, don't forget the two versions of BSB (British Standard Bastard ) achieved by forcing a Whitworth nut onto a BSF bolt or stud, or vice versa. Note that the resulting nut and bolt threads obtained by these two methods are not interchangable

[Bloggsworth]

Whitworth threads were designed for a purpose, not to annoy later generations of car restorers!

The different threads were to accommodate the vagaries of different materials and the manufacturing standards of the time, you'd have no joy stuffing a modern metric or UNF bolt into an 1860s aluminium casting as you'd never get it tight without stripping the thread in the casting, hence the deep cut and steep angles - He had threads for every occasion and every material. Sir Joseph Whitworth knew what he was about and pioneered the science of Metrology as he knew that without the means to measure accurately and reliably his quest for standardisation would be in vain.

[britishtrident]

Main reason for the UK standardising on Unified threads immediately after WW2 was to do with the military, even engines already in production such as the Roll-Royce B series were changed over to UNF and UNC threads.
It was only apparent after the experience of WW2 how much the US and Imperial systems of measurement had driffted apart.

[JtP1]

Quote

Originally posted by britishtrident
Main reason for the UK standardising on Unified threads immediately after WW2 was to do with the military, even engines already in production such as the Roll-Royce B series were changed over to UNF and UNC threads.
It was only apparent after the experience of WW2 how much the US and Imperial systems of measurement had driffted apart.

US and Imperial never drifted apart, they were never together. Weights and volume of items are different for similarly named quantities.