American threads

[SUNRAY]

Avoiding hijacking a thread.

Americans. AF stands for American Fine (not across flats as many incorrectly believe).

My experience of threads over the years is that USA, unlike UK, had national standards for their threads.
Originally there was USS which the Americans I used to work with (Ex USAF and prior to that Car manufacturing industry) referred to it as 'American Standard Thread' however I'll make an assumption it was really something like 'United States Standard' but I'll stress it is my assumption. IIRC it was established by one of the universities.
These threads were very coarse and a finer thread was introduced for Automobile applications refered to as SAE.
These two standards have been superceeded by 'Unified Thread Standard' (UTS) USS & SAE are now effecfively UNC & UNF plus UNEF (Unified Course, fine and extra fine).

No where have I heard of 'American Fine'. However again I'll stress I'm not a nut expert, I've never been to USA or worked in an American industry so my experience is not total.


I'd appreciate more information relating to 'American Fine' please.

 

[JohnW2]

No where have I heard of 'American Fine'. However again I'll stress I'm not a nut expert, I...

Nor have I, and nor am I (but my father definitely was a "thread expert" - but I can't ask him because he died over 50 years ago!) - although I have known of people (in addition to winston) who think that "AF" means "American Fine".

Even Mr Google knows almost nothing about it but, in terms of "once upon a time", this 1929 US document (click here) does describe such a thread - so maybe winston was actually born in, or fairly soon after, the 19th century??

Kind Regards, John

 

[ericmark]

I worked with BSW and BSF or British Standard Whitworth and British Standard Fine in the same was as ISO stands for international standards organisation and we get load of things from a water tank to film speed with an ISO number the united states used ASA (American Standards Association) and Germany used DIN.
Joseph Whitworth was a gun smith, we also had [url=https://en.wikipedia.org/wiki/British_Standard_CycleBritish] Standard Cycle thread[/URL] and British Association thread (BA)

As to American

United States Standard thread (USS thread), also known as Sellers Standard thread, Franklin Institute thread and American Standard thread, is a standard for inch based threaded

fasteners and washers.

The USS standard is no longer supported. It, together with the SAE fastener standard, was incorporated into the Unified Thread Standard. However, the term, USS, continues to be used occasionally today to describe inch based threaded fasteners with a coarse thread pitch and inch based washers that are a little bit larger than the corresponding SAE washer. The Unified Thread Standard uses the term UNC (Unified Coarse) to describe a fastener that previously would have been designated USS and the Unified Thread Standard uses the term UNF (Unified Fine) to describe a fastener that would have previously been designated SAE.

However for spanner sizes

The width across flats indicates the "size" of the spanner. It is imprinted on the spanners in millimeter (mm) values. Older British and current US spanners (wrenches) have inch sizes that are imprinted in intermediate sizes in fractions.

the head size does not always relate to thread size, some of the old British the nut and bolt had different spanner sizes. Also duel marked Whitworth and British Standard. There were some odd sizes, like 1 1/16" which really was a mm size. Today we even get metric moving spanners .[/quote][/quote]

 

[SUNRAY]

Nor have I, and nor am I (but my father definitely was a "thread expert" - but I can't ask him because he died over 50 years ago!) - although I have known of people (in addition to winston) who think that "AF" means "American Fine".

Even Mr Google knows almost nothing about it but, in terms of "once upon a time", this 1929 US document (click here) does describe such a thread - so maybe winston was actually born in, or fairly soon after, the 19th century??

Kind Regards, John

So I've joined in and asked Mr google, indeed yes there is a little about ANF and ANC threads which I fully appreciate could be abbreviated.
That said a 1/2" AF spanner does not fit a 1/2" ANF bolt head, or any other 1/2" bolt that I'm aware of.

I used to have a thread expert too, my mother was friendly with his wife and I fairly regularly used to drop her off/pick up etc. One day I happened to comment I needed a stud with 2 different threads (1/4" & 3/8" microphone which I think is BSW) he took me straight out to his shed and chucked a lump of manky green brass round bar in the lathe and turned the end down to size, flicked a few levers and cut the 1/4" thread. Then he asked if i wanted a wide area between the threads and the overall length, he took just enough off to to clean the side then turned it down for the 3/8" end and cut the thread. All without referring to any sort of chart. He did something similar for me with #10 24 left hand about 300mm long & M8 about 50mm long for some flapper valve actuators.

 

[SUNRAY]

I worked with BSW and BSF or British Standard Whitworth and British Standard Fine in the same was as ISO stands for international standards organisation and we get load of things from a water tank to film speed with an ISO number the united states used ASA (American Standards Association) and Germany used DIN.
Joseph Whitworth was a gun smith, we also had Standard Cycle thread and British Association thread (BA)

As to American

However for spanner sizes

the head size does not always relate to thread size, some of the old British the nut and bolt had different spanner sizes. Also duel marked View attachment 262954 Whitworth and British Standard. There were some odd sizes, like 1 1/16" which really was a mm size. Today we even get metric moving spanners View attachment 262955 .

[/quote][/QUOTE]
Thank you kindly sir, my previous almost agrees with you quotes. I'll take those anyday over my ramblings.

 

[JohnW2]

So I've joined in and asked Mr google, indeed yes there is a little about ANF and ANC threads which I fully appreciate could be abbreviated. That said a 1/2" AF spanner does not fit a 1/2" ANF bolt head, or any other 1/2" bolt that I'm aware of.

Agreed.

I used to have a thread expert too, my mother was friendly with his wife and I fairly regularly used to drop her off/pick up etc. One day ... took me straight out to his shed and chucked a lump of manky green brass round bar in the lathe and turned the end down to size, flicked a few levers and cut the 1/4" thread.....

My Dad was not a 'hands-on' thread person. He was an aeronautical engineer and for the last several years of his ridiculously short life (as I said, he died over 50 years ago, when I was 20), he was a Standards Engineer in the jet engine division of Rolls-Royce. He frequently talked, with enthusiasm, and even 'passion', about his work, but it seemed that all he ever talked about (or wrote about, or attended meetings about) were screw threads and turbine blades - and I have to say that I found it difficult to share his passion for such things

Kind Regards, John

 

[FrodoOne]

As stated in Post #2, see https://www.govinfo.gov/content/pkg...VPUB-C13-e37fe604c6638ab929cfb4fe8af50ac2.pdf (Page #8) for the start of the description of "American National Fine-Thread Series"


UNF : Unified National Fine superseded this in 1949

See https://www.sizes.com/tools/thread_american.htm - wherein it is stated
"The differences between American and British thread forms became a painful problem during the Second World War, especially in manufacturing and repairing airplane engines.
In 1948 representatives of Britain, Canada and the United States agreed on a Unified Standard.

In the compromise the British accepted the 60° thread angle, and the Americans accepted rounded roots and optionally rounded crests. Five classes of fit were defined.
The new fasteners continued to fit, for most practical purposes, ones manufactured under the old American National Standards. NC became UNC, NF became UNF, etc."

 

[bernardgreen]

Slightly off topic

In Germany adjustable spanners were and maybe still are referred to as being Ein Englander

An adjustable wrench (Verstellschlüssel) is called an Englishman (or person, if you prefer). According to Wikipedia (g), this is either because the first such wrench was patented in England, or because when German workmen encountered English nuts and bolts measured in inches, the adjustable wrench was the fastest and cheapest way to handle them.

 

[Mottie]

I've always thought that AF was the size in inches or fractions of inches Across the Flats of a bolt head. Same as metric spanner's -13mm Across the Flats of a bolt head.

 

[SUNRAY]

My Dad was not a 'hands-on' thread person. He was an aeronautical engineer and for the last several years of his ridiculously short life (as I said, he died over 50 years ago, when I was 20), he was a Standards Engineer in the jet engine division of Rolls-Royce. He frequently talked, with enthusiasm, and even 'passion', about his work, but it seemed that all he ever talked about (or wrote about, or attended meetings about) were screw threads and turbine blades - and I have to say that I found it difficult to share his passion for such things

Kind Regards, John

I know how frustrating it is when someone is so enthusiastic and ones interest can only extend so far.
As an example: One of the guys I worked with is a keen angler and he'd often come to work directly from an overnighter and he'd be full of the details...

 

[SUNRAY]

I've always thought that AF was the size in inches or fractions of inches Across the Flats of a bolt head. Same as metric spanner's -13mm Across the Flats of a bolt head.

I truly believe that to be the case too.

 

[SUNRAY]

As stated in Post #2, see https://www.govinfo.gov/content/pkg...VPUB-C13-e37fe604c6638ab929cfb4fe8af50ac2.pdf (Page #8) for the start of the description of "American National Fine-Thread Series"


UNF : Unified National Fine superseded this in 1949

See https://www.sizes.com/tools/thread_american.htm - wherein it is stated
"The differences between American and British thread forms became a painful problem during the Second World War, especially in manufacturing and repairing airplane engines.
In 1948 representatives of Britain, Canada and the United States agreed on a Unified Standard.

In the compromise the British accepted the 60° thread angle, and the Americans accepted rounded roots and optionally rounded crests. Five classes of fit were defined.
The new fasteners continued to fit, for most practical purposes, ones manufactured under the old American National Standards. NC became UNC, NF became UNF, etc."

Thanks for this, I'd always assumed our UNF, UNF threads were simply adopted from US but I thought we used different size heads as I had 5/16" UNF nuts and bolts scrounged from different sources for a carnival float and required 1/2" and 9/16" spanners and for 3/8" UNC required 9/16" & 5/8" spanners.

 

[EFLImpudence]

I've always thought that AF was the size in inches or fractions of inches Across the Flats of a bolt head. Same as metric spanner's -13mm Across the Flats of a bolt head.

I agree too.

I've just measured a couple of spanners I have to hand and they seem to be slightly larger than the stated size.
Obviously it would be a very tight fit if both nut and spanner were exactly the size.

So, even if AF doesn't officially stand for 'Across Flat', it still does.

 

[JohnW2]

I agree too. ... I've just measured a couple of spanners I have to hand and they seem to be slightly larger than the stated size. .... Obviously it would be a very tight fit if both nut and spanner were exactly the size. .... So, even if AF doesn't officially stand for 'Across Flat', it still does.

I think that all (but one) of us are agreed that, at least since 1949, there has been no thread officially known as "American Fine".

However, I don't think that there is any doubt that, at least for those 70+ years (if not 'for ever'), in relation to spanners etc. "AF" has always meant "across flats" - given that the "AF" dimension for such a tools IS the dimension 'across flats' - and totally different from any dimension of the thread of the nut or bolt for which it is applicable.

The same remains essentially true even for ring spanners. For example a "10mm" ring spanner fits the nut or bolt head for which a 10mm Across Flats open-ended spanner would fit.

Kind Regards, John

 

[cwhaley]

Lucky enough to have a Grandfather still alive in his mid-90s and he worked at Rolls Royce in Derby in the technical testing department, he also worked at a former company called International Combustion. He says they only every referred to these types of nut heads as 'Across Flats'. His period of working at these firms was between the mid-'50s and early '70s.

The only connection to America he did have was when a group of Americans visited one of the works where there were large lathes working away (this was in the 1960s). He said that before they arrived, they had to cover up some of the dates on the machines out of embarrassment as at least one had a large year plate on it saying "1924"!