Are A/F imperial?
Mr Whippy - 16/3/23 at 02:06 PM
Hi,
I have a lot of imperial size spanners and sockets, are these the same as what they call A/F i.e. I don't have to buy more tools??
Sorry for the stupid question...
Ta.
[Edited on 16/3/23 by Mr Whippy]
gremlin1234 - 16/3/23 at 02:20 PM
A/F stands for across flats, ie how big the head of the bolt is.
imperial spanners are usually measured this way. but then the metric ones are too. - a 13 mil socket fits a bolt head that is 13mm across flats
but there are whitworth spanners as well and they are as generally sized by the thread diameter. [except at one point the head sizes change to save
steel...]
[Edited on 16/3/23 by gremlin1234]
Mr Whippy - 16/3/23 at 03:32 PM
ok thanks, just seemed a bit odd not to call them imperial?! I'm glad I never threw them out!
mcerd1 - 16/3/23 at 05:02 PM
quote:
Originally posted by Mr Whippy
ok thanks, just seemed a bit odd not to call them imperial?! I'm glad I never threw them out!
its because the older whitworth ones had spanner sizes that were the bolt diameter not the head size
so a 1/2" whitworth bolt needs a 1/2" whitworth spanner (which actually measures 0.82" or ~13/16" across the flats)
if you've got old whitworth spanners they sometimes have both sizes cast / stamped into them..
AF sizes are called that as its the American standard that only became common here during/after WWII - these are are for UNF / UNC threaded bolts
(Unified National Course / Fine - but the national bit means USA)
vs the older BSW / BSF (British Standard Whitworth / Fine - ie the one we'd used since the 1840's ) - these are totally different
threads and have no compatibility at all with the American stuff.
if you can believe it we still use BSW bolts now for some jobs 
[Edited on 16/3/2023 by mcerd1]
Mr Whippy - 16/3/23 at 08:03 PM
Thanks for the explanation, it all seems very complicated. I think I have the right ones though.
peter030371 - 17/3/23 at 09:34 AM
quote:
Originally posted by gremlin1234
a 13 mil socket fits a bolt head that is 13mm across flats
[Edited on 16/3/23 by gremlin1234]
Just to be a pedant 
No it doesn't....13mil is NOT 13mm. A Mil is a unit of measure that equals a thousandth of an inch and using it as
'slang' for mm is misleading to people (like me) that use Mil in everyday life i.e at work for designing PCBs some parts of which are still
specified in Mil and some parts in mm!
I am odd and often get funny looks when I ask for (random example) 'a 2mm rod' and they come back and say 'I have 2.5mil will that
do' and I then say '2.5mm is fine' or words to that effect 
I know I can't change the world but I can only hope 
gremlin1234 - 17/3/23 at 09:50 AM
quote:
Originally posted by peter030371
quote:
Originally posted by gremlin1234
a 13 mil socket fits a bolt head that is 13mm across flats
[Edited on 16/3/23 by gremlin1234]
Just to be a pedant No it doesn't....13mil is NOT 13mm. A Mil is a unit of measure that equals a thousandth of an inch and using it as
'slang' for mm is misleading to people (like me) that use Mil in everyday life i.e at work for designing PCBs some parts of which are still
specified in Mil and some parts in mm!
I am odd and often get funny looks when I ask for (random example) 'a 2mm rod' and they come back and say 'I have 2.5mil will that
do' and I then say '2.5mm is fine' or words to that effect
I know I can't change the world but I can only hope
pedantry approved
indykid - 17/3/23 at 10:21 AM
quote:
Originally posted by peter030371
quote:
Originally posted by gremlin1234
a 13 mil socket fits a bolt head that is 13mm across flats
[Edited on 16/3/23 by gremlin1234]
Just to be a pedant No it doesn't....13mil is NOT 13mm. A Mil is a unit of measure that equals a thousandth of an inch and using it as
'slang' for mm is misleading to people (like me) that use Mil in everyday life i.e at work for designing PCBs some parts of which are still
specified in Mil and some parts in mm!
I am odd and often get funny looks when I ask for (random example) 'a 2mm rod' and they come back and say 'I have 2.5mil will that
do' and I then say '2.5mm is fine' or words to that effect
I know I can't change the world but I can only hope
If you're going to complain about mil, you should at least use milliinch in its full form instead of its slang form or question "milliinch
or millimeter?"
Milliinch has no place in the imperial system. It's just lazy not using 1024ths.
Sanzomat - 17/3/23 at 10:59 AM
For some reason that reminded me of my "favourite" drawing scale of all time. I'm a construction guy and drawings are nearly all scaled
as a simple ratio 1:50, 1:100 etc so can't go wrong and that ratio works whether you are using metric or imperial.
A few years ago we were pricing a building project for Dowty in Cheltenham (that probably dates it a bit in itself). The building had been designed by
their in house engineers rather than using an architect as it was a simple "shed" for some new machine tools. The scale on the drawings was
given as 2mm:1ft
gremlin1234 - 17/3/23 at 04:47 PM
quote:
Originally posted by Sanzomat. The scale on the drawings was given as 2mm:1ft
2mm scale is quite common in model building,
OO gauge is 4mm scale (4mm to foot 1:76.2) for the bodies - but uses a different scale for the track!
gremlin1234 - 17/3/23 at 05:59 PM
quote:
Originally posted by indykid
If you're going to complain about mil, you should at least use milliinch in its full form instead of its slang form or question "milliinch
or millimeter?"
Milliinch has no place in the imperial system. It's just lazy not using 1024ths.
I know a milliinch as '1 thou'
imperial measurements are weird
base 3 foot in a yard
base 12, pennys (d) in shilling and inches in a foot
base 14 pounds in stone
16 ounces in pound weight
20 shilling in pound money
21 shilling in Guinea
and that's before we get t the troy measurements...
or measurement of length and area with Chains, Acres etc.
mcerd1 - 17/3/23 at 06:28 PM
quote:
Originally posted by gremlin1234
I know a milliinch as '1 thou'
Same here 'thou' is the correct term in the UK for 0.001" (ie thousandths of an inch)
most old machine tools are marked up in thou as are imperial vernier calipers, but the actual marking will just be 0.001" to avoid
confusion with the americans...
David Jenkins - 17/3/23 at 08:35 PM
quote:
Originally posted by gremlin1234
A/F stands for across flats, ie how big the head of the bolt is.
imperial spanners are usually measured this way. but then the metric ones are too. - a 13 mil socket fits a bolt head that is 13mm across flats
but there are whitworth spanners as well and they are as generally sized by the thread diameter. [except at one point the head sizes change to save
steel...]
[Edited on 16/3/23 by gremlin1234]
If you're talking about spanners for your vintage car, then you'll probably need either BSW (British Standard Whitworth) or BSF (British
Standard Fine).
And, just to confuse the issue, the size of BSW bolts and nut hexes was reduced to save metal, so you will often find old spanners that have both BSW
and BSF sizes on them, but for different diameter threads!
I much prefer the simplicity of metric and A/F sizes...
Theshed - 18/3/23 at 01:47 PM
The thread form of BSW nuts and bolts is by far superior to either metric or imperial threads. By about 1980 BL cars had all three types in use at the
same time.
nick205 - 18/3/23 at 02:04 PM
Maybe it's my age (49), but I consider myself a metric generation.
Have a few Imperial spanners (3/4", but mainly for plumbing parts I've had to tackle over the years.
gremlin1234 - 18/3/23 at 02:21 PM
quote:
Originally posted by Theshed
The thread form of BSW nuts and bolts is by far superior to either metric or imperial threads. By about 1980 BL cars had all three types in use at the
same time.
I think they also had BA British Association fittings on some of the electrical parts too
David Jenkins - 18/3/23 at 02:31 PM
quote:
Originally posted by gremlin1234
I think they also had BA British Association fittings on some of the electrical parts too
BA is a metric thread! It's specified in metric measurements anyway, albeit rather eccentric ones. This is a total PITA when you want to cut a
thread on an imperial lathe, as I occasionally had to do when I did model engineering.
Wikipedia link
gremlin1234 - 18/3/23 at 03:11 PM
quote:
Originally posted by David Jenkins
BA is a metric thread! It's specified in metric measurements anyway, albeit rather eccentric ones.
yep but its also a different spanner size
David Jenkins - 19/3/23 at 10:16 AM
quote:
Originally posted by gremlin1234
quote:
Originally posted by David Jenkins
BA is a metric thread! It's specified in metric measurements anyway, albeit rather eccentric ones.
yep but its also a different spanner size
True - irrelevant, but very true. As in "tiny".
Most BA screws in vehicles are slotted or cross-point heads though. I can't say that I've ever seen a hex head BA screw in any car.
jacko - 19/3/23 at 08:14 PM
Not to forget unf nuts and bolts
David Jenkins - 19/3/23 at 10:02 PM
I had a pal in the local model engineering club who preferred to use "Unified Cycle Gas Thread"... but he could be a pillock at times!
mcerd1 - 20/3/23 at 08:22 AM
quote:
Originally posted by nick205
Maybe it's my age (49), but I consider myself a metric generation.
I'm definitely part of the metric generation (41) but I grew up working on all kinds of old stuff from 1930 onwards with my dad and his uncle
(who'd been a mechanic since the early 1940's) - so I've always had a mixture of different standard at the same time
It turned out to be a good education, at work we are still having to specify and supply BSW bolts to this day
(Working to imperial drawings from the 1950's)
If you're working with mix of stuff you really need a set of calipers (digital ones are pretty cheap now) and a set of thread gauges
Also some sort of reference book helps - I grew up with one of these next to the toolbox:
https://www.amazon.co.uk/Precision-Reference-Drawing-Toolroom-Workshop/dp/B0000CLZUO
[Edited on 20/3/2023 by mcerd1]
[Edited on 20/3/2023 by mcerd1]
James - 21/3/23 at 07:12 PM
quote:
Originally posted by peter030371
quote:
Originally posted by gremlin1234
a 13 mil socket fits a bolt head that is 13mm across flats
[Edited on 16/3/23 by gremlin1234]
Just to be a pedant No it doesn't....13mil is NOT 13mm. A Mil is a unit of measure that equals a thousandth of an inch and using it as
'slang' for mm is misleading to people (like me) that use Mil in everyday life i.e at work for designing PCBs some parts of which are still
specified in Mil and some parts in mm!
I am odd and often get funny looks when I ask for (random example) 'a 2mm rod' and they come back and say 'I have 2.5mil will that
do' and I then say '2.5mm is fine' or words to that effect
I know I can't change the world but I can only hope
Think yourself lucky.
My Missus refers to any measurement, distance or liquid, as "millimums"! As we're doing up a house it can cause quite some
consternation!
mgb281 - 21/3/23 at 08:53 PM
quote:
Originally posted by nick205
Maybe it's my age (49), but I consider myself a metric generation.
Have a few Imperial spanners (3/4", but mainly for plumbing parts I've had to tackle over the years.
BSP (British Standard Pipe) thread is a universal plumbing and hydraulic pipe and fittings thread and vis actually a Whitworth thread. If you think
imperial sizes are archaic just delve into metric hydraulic fittings, French and Japanese metric fittings are totally incompatible
I buy fuel in litres but measure consumption in miles per gallon. I calculate herbicide dilution in litres per hectare but apply it at gallons per
acre. Those of us who were fluent with imperial soon became equally fluent with metric and are easily able to mix and match.
David Jenkins - 21/3/23 at 09:20 PM
I wish the UK would commit to going metric ASAP - just about everyone up to 30 (maybe older?) has only been taught metric, never taught imperial, and
they simply don't understand the old measurements.
Though I was surprised one day in the local pub when an old boy of 80+ announced that he'd just planted 3 metres of broad bean seedlings!
[Edited on 22/3/23 by David Jenkins]
MikeR - 22/3/23 at 12:29 PM
Having spent many a weekend with my dad (ex time served old school engineer) under a mini in my teens I'm fully conversant with mills
(millimeter), thous (thousands of an inch) and variations of measurement eg it needs an 8th taking off (trim by about 3mm).
I also got to the point I could supply the correct spanner across metric, Imperial and whitworth without checking (some bolts on a 20 year old early
70s mini were worn so you had to use the spanner that fitted, not the size it was supposed to be)
scudderfish - 22/3/23 at 12:58 PM
quote:
Originally posted by gremlin1234
quote:
Originally posted by Sanzomat. The scale on the drawings was given as 2mm:1ft
2mm scale is quite common in model building,
OO gauge is 4mm scale (4mm to foot 1:76.2) for the bodies - but uses a different scale for the track!
Tyres annoy me. 205/55/R17 is a metric measurement, a ratio and an imperial measurement all in one specification!