American threads

[JohnW2]

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 ....

As I said, my father died 50+ years ago, very 'prematurely', but if he hadn't, he would only be 98 today, so much the same vintage as your grandfather. In latter years, he was based at Leavesden (Herts), but very frequently travelled to Derby

... 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.

That's consistent with what everyone else (other than one) is saying here. As you say, this talk about ';across flats' (the current accepted meaning of "AF" refers to nuts, bolt heads and spanners etc., and has absolutely nothing to do with any specific thread, "American Fine" (70+ years ago!) or anything else!!

Kind Regards, John

 

[cwhaley]

As I said, my father died 50+ years ago, very 'prematurely', but if he hadn't, he would only be 98 today, so much the same vintage as your grandfather. In latter years, he was based at Leavesden (Herts), but very frequently travelled to Derby Kind Regards, John

Derby made a lot in those days. Not a lot of engineering talent left outside of Royce's now unfortunately -- aside from making Japanese cars and fancy crockery!

That's consistent with what everyone else (other than one) is saying here. As you say, this talk about ';across flats' (the current accepted meaning of "AF" refers to nuts, bolt heads and spanners etc., and has absolutely nothing to do with any specific thread, "American Fine" (70+ years ago!) or anything else!!

That makes sense, just thought I'd add another bit of weight and personal history to the argument. Being a young man in my 30s, I chiefly work in 'old measurement' as I inherited a lot of Imperial spanners/socket sets and my project car was made with UNF bolts.

 

[winston1]

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??

No, not that old. But the AF information was given to me over 50 years ago by someone who was about to retire.

 

[JohnW2]

No, not that old. But the AF information was given to me over 50 years ago by someone who was about to retire.

Fair enough - but, as Frodo pointed out, the American Fine (and American Coarse) series of threads (described in the 1929 document to which I linked) were superseded (by the 'unified' UNF and UNC) in 1949 - so >70 years ago.

In any event, the important point is that, as I said, the 'Across Flats' figure for a spanner has absolutely nothing to do with the dimensions, let alone type, of the thread of the nut or bolt for which the spanner is suitable - and such tools have been identified with such an "AF" figure for the entirety of my life to date, if not longer.

 

[JohnW2]

Derby made a lot in those days. Not a lot of engineering talent left outside of Royce's now unfortunately -- aside from making Japanese cars and fancy crockery!

Indeed.

That makes sense, just thought I'd add another bit of weight and personal history to the argument. Being a young man in my 30s, I chiefly work in 'old measurement' as I inherited a lot of Imperial spanners/socket sets and my project car was made with UNF bolts.

Similar here. I inherited (and still have/use) a lot of Imperial tools from my father, and the first couple of cars I had (and worked on extensively in late 60s/early 70s), certainly had only Imperial fasteners.

Kind Regards, John

 

[Astra99]

When I was apprenticed, many years ago, one of the older mechanics asked me what "AF" meant. "Across the Flats" I replied. "No! All to F***!" said he. Picking up on JohnW2's post, the Morris 1000 and Austin A35 shared mechanicals. The Austin was 100% UNF/UNC, but only the Morris 1000 engine had AF sizes, all the rest of the fixings were BSF/BSW, including the ends on the brake pipes! Most of us young chaps didn't have many BSF/BSW spanners, so if we took out a Moggy Thou engine, all the nuts and bolts holding the engine and gearbox together were replaced with UNF!

 

[SUNRAY]

Indeed.
Similar here. I inherited (and still have/use) a lot of Imperial tools from my father, and the first couple of cars I had (and worked on extensively in late 60s/early 70s), certainly had only Imperial fasteners.

Kind Regards, John

I started purchasing my own tools in 1973, my first cars (Viva, Maxi, Imp & Bedford CA) were exclusively imperial sizes, the next were 1977 & 1981 Cortinas which both seemed to have a confusing mixture.

If I'm being honest, the vast majority of my fathers tools were really cheap quality and disinherited (if such a word exists/appropriate) in other words dumped.

 

[JohnW2]

... Picking up on JohnW2's post, the Morris 1000 and Austin A35 shared mechanicals. The Austin was 100% UNF/UNC, but only the Morris 1000 engine had AF sizes, all the rest of the fixings were BSF/BSW, including the ends on the brake pipes! ...

Maybe it's just me, but I'm not clear what you are saying there - are you using "UNF/UNC" synonymously with (their predecessors) "AF/AC" (to contrast with BSF/BSW)?

Anyway, returning to the "AF" issue, I've just had a look at some of my father's spanners (probably 70-75 years old). Many have sizes cast or engraved on them described as "AF". For example, the left and middle ones in the photo below are marked "5/8 AF" and "9/16 AF" respectively, clearly far to small to fit a nut or head of a bolt with 5/8" or 9/16" threads of any type - and, indeed, have measured openings 'across flats' of approximately 5/8" and "9/16" respectively. On the other hand, the one on the right also has an opening of approximately 9/16" ('across flats'), but is marked "5/16 W", hence presumably designed to fit a nut or head of a bolt with a 5/16" Whitworth thread.

So, at least when it appeared as a marking on spanners, "AF" definitely meant "Across Flats", and had absolutely nothing to do with the thread of the fastener (whether Fine, Coarse, American, British or anything else)!

Kind Regards, John

 

[SUNRAY]

Maybe it's just me, but I'm not clear what you are saying there - are you using "UNF/UNC" synonymously with (their predecessors) "AF/AC" (to contrast with BSF/BSW)?

Anyway, returning to the "AF" issue, I've just had a look at some of my father's spanners (probably 70-75 years old). Many have sizes cast or engraved on them described as "AF". For example, the left and middle ones in the photo below are marked "5/8 AF" and "9/16 AF" respectively, clearly far to small to fit a nut or head of a bolt with 5/8" or 9/16" threads of any type - and, indeed, have measured openings 'across flats' of approximately 5/8" and "9/16" respectively. On the other hand, the one on the right also has an opening of approximately 9/16" ('across flats'), but is marked "5/16 W", hence presumably designed to fit a nut or head of a bolt with a 5/16" Whitworth thread.

So, at least when it appeared as a marking on spanners, "AF" definitely meant "Across Flats", and had absolutely nothing to do with the thread of the fastener (whether Fine, Coarse, American, British or anything else)!

View attachment 263178

Kind Regards, John

IIRC 5/16"W is roughly half way between those 2 AF's.

 

[JohnW2]

IIRC 5/16"W is roughly half way between those 2 AF's.

You're very probably right - I only measured roughly/quickly with a ruler.

However, as I'm sure you understand, my point was that whilst spanners with "W" size markings clearly do relate to the size of the Whitworth thread of nuts/bolts for which it is suitable, when spanners are marked with an "AF" size that does not refer to thread size but, rather, merely to their 'across flats' dimension. Don't forget that this all started because of ...

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

... if thiose who manufactured the two "AF" spanners I illustrated shared that view, they clearly would not have put "5/8 AF" and "9/16 AF" markings on spanners which were clearly far too small to use with nuts/bolts which had (pre-1949 ) 5/8" or 9/16" American Fine threads

It seems that, again, he spread misinformation.

Kind Regards, John

 

[Keithmac]

Most American vehicles manufactured over last 15 years or more have gone over to metric fasteners.

I bought a load of Imperial kit for working on Harley Davidson's and even they have gone metric (amusingly when you get genuine Harley parts they have "made in China" on the packaging).

The idea of sizing a bolt or fastener due to the size of it's head is definitely an odd one!.

 

[JohnW2]

Most American vehicles manufactured over last 15 years or more have gone over to metric fasteners.

I suppose it had to happen eventually, particularly if they have an interest in non-US markets, even though they remain 'out on a limb' in relation to so many other things.

... The idea of sizing a bolt or fastener due to the size of it's head is definitely an odd one!.

It is - but I'm not sure it is appreciably more odd than the idea of sizing a spanner by the thread size of a nut/bolt/screw whose head it 'happens to fit' (as in the "5/16 W" one I illustrated) - after all, although relatively rarely, one does sometimes use a spanner for purposes unrelated to threaded items, in which case it is definitely the 'across flats' dimension which matters!

Kind Regards, John

 

[SUNRAY]

You're very probably right - I only measured roughly/quickly with a ruler.

However, as I'm sure you understand, my point was that whilst spanners with "W" size markings clearly do relate to the size of the Whitworth thread of nuts/bolts for which it is suitable, when spanners are marked with an "AF" size that does not refer to thread size but, rather, merely to their 'across flats' dimension. Don't forget that this all started because of ...

... if thiose who manufactured the two "AF" spanners I illustrated shared that view, they clearly would not have put "5/8 AF" and "9/16 AF" markings on spanners which were clearly far too small to use with nuts/bolts which had (pre-1949 ) 5/8" or 9/16" American Fine threads

It seems that, again, he spread misinformation.

Kind Regards, John

I wasn't trying to contradict you in any way.
Years back, in fact 1977-8, I made up some loudspeaker brackets which included various mounting and locking bolts. As luck would have it, where I worked there was constant equipment updating/increasing and the preceeding rack arrangements were removed and 9 out of 10 times scrapped. Aquiring Whitworth nuts and bolts was commonly as easy as sweeping them up. Most venues tended to have stash held 'in stock' and generally for private jobs.
Accordingly those were my obviuos choice. As mentioned before I had friends in similar situations and sometimes I ended up with UNF/UNC for following projects. As mentioned I found those didn't always have the same head size, then metric joined the mix too, so I got quite good at recognising head sizes and appropriate spanner required.

 

[SUNRAY]

The idea of sizing a bolt or fastener due to the size of it's head is definitely an odd one!.

It is - but I'm not sure it is appreciably more odd than the idea of sizing a spanner by the thread size of a nut/bolt/screw whose head it 'happens to fit' (as in the "5/16 W" one I illustrated) - after all, although relatively rarely, one does sometimes use a spanner for purposes unrelated to threaded items, in which case it is definitely the 'across flats' dimension which matters!

Kind Regards, John

I have to disagree here, historically spanners were marked with thread size, if you happened to know the thread size it was easy to select the correct spanner first time (albeit I've encountered different heads for a thread size fairly often. On this point I'll even say I've purchased bolt sets with bolt head and nut sizes being different). How many people know the raft of different head sizes, how many can instantly tell the difference between the heads of 5/16"UNC, M8, 1/4"W, 5/16BS? How many have rounded a nut by using the wrong size spanner?

 

[JohnW2]

I have to disagree here, historically spanners were marked with thread size ...

They were - I have countless like the one I illustrated.

... if you happened to know the thread size it was easy to select the correct spanner first time...

Very true, but that's a big "if", at least for me.

When I am working on something (car, washing machine or whatever) when I first have a need for a spanner for a particular nut, screw or bolt, I will very often not even have sight of, let lone knowledge of the type and size of, the associated thread - but what I can see, feel or even measure, is the required 'across flats' dimension of a spanner that will fit it - and that is the basis on which I necessarily have to select my 'first try' spanner!

Kind Regards, John