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UNC and UNF fasteners in Britain

39 Replies

Re: UNC and UNF fasteners in Britain

Posted by Roger Bryant on Jun 19, 2019 7:40 am


So half the problem solved 😀 I think that trying to remove the damaged threads is the best solution. They were probably damaged by someone trying to use the wrong thread, possibly metric ☹

When you have got your machines in good working order here's a project suggestion: A breath powered piston valve engine, 6mm bore.

26bcc62cefae1506dd43de98fbf50dee-huge-ds

https://youtu.be/qoLbLisxNLU

It's good as an icebreaker when starting to talk about engineering, just take it out of your pocket and give a blow (it also doesn't smell like my IC models do)

Best regards

Roger

Re: UNC and UNF fasteners in Britain

Posted by Andy Millar on Jun 19, 2019 11:32 am

Yes, I like those, I'd also like to have a go at a miniature Stirling engine sometime - but many other projects to come first!

Most likely along these lines is that I'd finally properly make something at the other end of the scale. About 15 years ago I built a 3m high 3m long beam atmospheric engine with a group of 10-12 year olds, to show them what used to be in the engine houses that surround us in SE Cornwall. It was hugely successful, and we showed it at several events, but we did rather cheat by powering it by a vacuum cleaner. (I was the health and safety governor at the school where we built it so thought I should be a little bit careful!) Ever since then I've wanted to try again, but actually making it steam powered - the nice thing is that it can be at VERY low pressure, but in turn this means a better piston seal than we were able to make at the time. But again, a few other jobs to come first.

You may have noticed I've kept very quiet about how those threads got damaged, I do know exactly how it happened. The machine was donated to me back when I was running the above schools' engineering club, but we had a very short window to dismantle and move it. ("If you can move it yourselves this lunchtime you can have it, otherwise it's going for scrap.") If we'd had a suitable sized three legged puller and a suitable spacer block it wouldn't have happened, what we did have was a number 4 Birmingham screwdriver. I shall say no more and move on before a hollow square is formed and my CEng is ceremoniously removed...

Anyway all sorted now, a gentle bit of drilling got rid of the mangled threads, and I found another screw on the machine which was the same size and which I could measure accurately. The biggest challenge last night was finding somewhere that sold 3/16" BSF x 3/4" cap head bolts! But they're on order now.

Coffee time over,

Cheers,

Andy
 
Andy Millar CEng CMgr IET Mentor / IET PRA uk.linkedin.com/in/millarandy

Re: UNC and UNF fasteners in Britain

Posted by Denis McMahon on Jul 1, 2019 6:36 am

Arran Cameron:
Somebody will know the answer to this…

Almost all British machinery manufactured before 1950 used Whitworth, BSF, or BA fasteners. Manufacturers moved towards using metric fasteners in the 1970s and these have been the most commonly available and used family since 1980, although the proposal to use metric fasteners dates back 1965. Whitworth and BSF officially became obsolete in 1948 following an agreement between the UK, US, and Canada to standardise on the American UNC and UNF fasteners for future use. UNC and UNF fasteners were used in British machinery manufactured in the 1950s, 60s, and 70s where they gradually replaced Whitworth and BSF before themselves being replaced by metric fasteners.

1. Were UNC and UNF fasteners used across most industries in the UK or were they largely confined to specific industries such as automotive and machine tools? Were they regularly used in railways or shipbuilding?
2. Were the numbered sizes smaller than ¼ inch commonly used or did industry stick with BA fasteners until they moved to using metric fasteners?
3. Were UNC and UNF fasteners commonly used in construction? What are the most common family of fasteners used to hold together 1960s tower blocks and university buildings?
4. Was it easy to buy UNC and UNF fasteners from hardware and DIY shops in the 1960s and 70s or did they move directly from selling Whitworth and BA fasteners to metric fasteners?

 
I have read this whole thread with great interest.

 If Whitworth and BSF became officially obsolete in 1948, then my observations suggest that many industries ignored officialdom. This is possibly just as well. Many industries in the 1950s probably had the foresight to recognise that the standard used in countries where the metric system was well established - the standard now known as Isometric - was the "band waggon". A planned and phased move to that standard when the  time was ripe was preferable to converting to American standards with the prospect of a further conversion later.

To answer the initial questions:

1.  I served my time in the 1960s in the electricity supply industry. There, Whitworth and BSF were dominant and in continuing use by plant manufacturers.  I came across American Unified fasteners mainly on motor cars. At the time I put this down to the dominance of American organisations like Ford and GM. Ford was later a key player in the automotive industry's conversion to Isometric.

2. I believe that the smallest Whitworth size was 1/8 inch. I came across this size in domestic appliances but it was rarely found in the industrial environment, where the BA series was more popular for fasteners of this size. Whitworth sizes were popular from 3/16 inch upwards.

3. I have little experience of the construction industry at that time. On theatre electrical equipment, I came across both UNC and Whitworth. This caused confusion because the two standards were similar but not quite identical. A nut of one could sometimes be forced onto a screw thread of the other - not recommended practice of course. Confusion was further caused by the nut sizes (across the flats) being different.

4. I have long thought that a lot of obsolete stuff, surplus to industry's requirement, gets dumped on the home DIY market. The move from Whitworth to Isometric was somewhat sporadic, with Unified occasionally getting in the way. I remember once around 1975 in a hardware store, asking for some Isometric fasteners, and being told, rather pompously, "They will never catch on for years yet." Six months later, the  same shop was selling almost exclusively Isometric

Re: UNC and UNF fasteners in Britain

Posted by mapj1 on Jun 5, 2019 4:09 pm

I fear, as 2BA is about 4 or 5mm dia, and thread pitch 0.81mm  (0BA is practically M6, 6mm dia, and 1mm pitch, and each higher  BA size is 90% of the dimensions of the preceding.)
You may not find it possible to get a gauge that is thin enough to fit down hole and engage sufficiently convincingly to be sure. Depending on the hole depth and the how much is damaged it may be safer to taper ream the damaged turns until a bolt fits. (and note that a brass bolt will reveal binding without damaging the steel, though go gently, you do not wish to snap the head off.)
regards Mike

As others have pointed out, the BA range was essentially metric based. 0BA is practically the same as M6 with a thread pitch of 1 mm but the thread profile is different. Other BA sizes do not have such clear round dimensions, though there is a logical system. I think one reason why BA did not catch on is because people prefer, to gauge numbers, sizes relating to actual physical dimensions in recognised measurement units, so that bolts can be easily related to bolt hole clearances, etc. To give a parallel example, the gauge sizes for self-tapping wood screws had a good purpose in the mid-20th century, but nowadays the actual thickness in millimetres is preferred. I remember a fiasco in the mid 60s when fitters requested the factory store to issue some sheet metal. Their request was in actual thickness as measured with a micrometer, but the storeman only knew gauge numbers. Two hours were wasted until someone found a conversion chart.

I recently required some 4BA screws for an electrical job. The nearest to this you can buy in shops nowadays is M3·5. I got what I wanted from E-bay without difficulty.
Denis McMahon, BSc, MIET, MBCS, PGCE

Re: UNC and UNF fasteners in Britain

Posted by Andy Millar on Jul 1, 2019 10:12 am

Denis McMahon:
I think one reason why BA did not catch on is because...

Hi Denis,

Actually I think BA was pretty successful in the UK, but just in - as you sort of suggest - those niche industries where all the fastenings were of small dimensions. It seemed pretty standard across the electronics industry when I started. British Rail signalling was largely constructed out of BA screws - and large bits of it still are! (For interest I just checked the current Unipart Rail Catalogue - the UK Rail Industry's equivalent to the RS Catalogue - and it still lists a huge range of BA fixings available for sale.) IIRC, the Post Office telephone system was BA based too.

But of course once ISO came in to the UK it was much easier to use that everywhere for new designs.

Couldn't agree more that eBay is our friend here, I've also been buying BA screws (because I occasionally dabble in model engineering) as well as the above discussed-to-death BSF. It's strange that it's much easier to buy these sizes now than it was 15 years ago, just because it's easier to locate those companies that supply them. Nice mix of old and new technologies coming together.

Cheers, Andy
 

Andy Millar CEng CMgr IET Mentor / IET PRA uk.linkedin.com/in/millarandy

Re: UNC and UNF fasteners in Britain

Posted by Denis McMahon on Jul 2, 2019 4:54 pm

Thanks for your reply, Andy. Yes of course BA was successful in its day and served its purpose well. In my industry I came across BA sizes in instruments and other small assemblies. I was used for many other purposes, including bicycles.

In the 60s I had a Suzuki motor bike and Renault car, so I came across metric fasteners there, and bought myself a set of metric spanners (which I still have to this day). My first experience of Isometric fasteners in industry was in 1973 when I worked for a while for a subsidiary of Philips.

As you say, modern on-line shopping is marvelous for procuring "impossible" things. I have a Christmas tree lighting set from the 1950s which now has great sentimental value and I can still get spare bulbs to keep it going.
Denis McMahon, BSc, MIET, MBCS, PGCE

Re: UNC and UNF fasteners in Britain

Posted by Andy Millar on Jul 4, 2019 7:38 pm

It was my Renault 4 which I got in about '78 that caused me to get the metric spanners and socket set which I sill use - that whole engine could be removed and stripped down with (IIRC)  10mm and 17mm sockets and spanners! I had a lot of fun with that car, shame about the rust that killed it...

Cheers, Andy
Andy Millar CEng CMgr IET Mentor / IET PRA uk.linkedin.com/in/millarandy

Re: UNC and UNF fasteners in Britain

Posted by Denis McMahon on Jul 7, 2019 8:44 am

Yes, Andy, mine was also a Renault 4, though I did not attempt anything as ambitious as removing the engine. An interesting point was the lock-nutting arrangement, used on the clutch adjustment and similar. It used adjacent sized spanners, probably recognising that spanner sets usually came in 1 mm intervals and a handyman might be less likely to have two spanners of exactly the same size. In reality, only certain spanner sizes are "standard", relating to the corresponding standard sized bolts. A set of metric spanners would probably tackle nearly all nut sizes at a pinch, though I still have a set of BS ones.

Rust was usually what killed cars in those days.  Things have certainly improved and you seldom see a rusty car nowadays and plenty of twenty-plus-year-old ones are still running around. What finishes cars nowadays are usually MOT issues, serious mechanical failure or accident damage, where repair is not economical.

I had fun with my Renault 4 too, a versatile, practical and comfortable car. I sold it on before rust became a problem.
Denis McMahon, BSc, MIET, MBCS, PGCE

Re: UNC and UNF fasteners in Britain

Posted by Arran Cameron on Jul 9, 2019 4:45 pm

Denis McMahon:
I was used for many other purposes, including bicycles.

I always thought they used British Standard Cycle threads before many of them were replaced with metric threads. Modern day components made in the US often use UNC and UNF threads.

Re: UNC and UNF fasteners in Britain

Posted by Denis McMahon on Jul 10, 2019 8:36 am

In the 1960s bicycles were a bit of a mixture of thread types. BA seemed to be used for some of the smaller bolts, e.g. fixing mudguard stays to frame. The system was also slightly confused by the similarity of BSC to BSF in some sizes. I once had to replace a lost bolt on a prop-stand, and I used a 1/4 inch BSF one, easy to obtain. I "cleaned up" the thread with a  tap and it fitted OK. In reality it was probably a replacement for a BSC bolt. Both BSC and BSF 1/4 inch are 26 threads per inch, with a slight difference in thread profile. Indeed these are very similar to 0BA and M6, which have thread pitches of 1 mm or 25·4 threads per inch. I read somewhere that one type will screw onto the other provided the threaded section is not too long.

I believe that the British Cycle threads are still used on "cycle specific" parts, such as threads associated with bearings, for which the fine thread form is highly suitable. 
Denis McMahon, BSc, MIET, MBCS, PGCE

Re: UNC and UNF fasteners in Britain

Posted by Arran Cameron on Jul 10, 2019 11:31 am

Denis McMahon:
In the 1960s bicycles were a bit of a mixture of thread types. BA seemed to be used for some of the smaller bolts, e.g. fixing mudguard stays to frame.

Manufacturers and installers of aftermarket accessories probably used whatever fasteners they could obtain most easily at the lowest price.


I believe that the British Cycle threads are still used on "cycle specific" parts, such as threads associated with bearings, for which the fine thread form is highly suitable. 

There are still a few BSC thread sizes in regular use today although nuts fit metric spanners. A 5/16" Whitworth spanner is the size that fits pedals as well as axle nuts on small children's bikes, and is by co-incidence almost the same size as a 15mm spanner. A 17mm spanner fits the nuts used on 3/8" diameter axles (often erroneously referred to as 10mm) but this is a standard metric spanner with no Whitworth equivalent.

Female BMX hubs are attached to the frame with a strange hybrid bolt that is 3/8" UNF (24 TPI as opposed to 26 TPI for BSC of the same diameter) with a 17mm head. 

 

Re: UNC and UNF fasteners in Britain

Posted by Arran Cameron on Jul 15, 2019 5:34 pm

Denis McMahon:

1.  I served my time in the 1960s in the electricity supply industry. There, Whitworth and BSF were dominant and in continuing use by plant manufacturers.  I came across American Unified fasteners mainly on motor cars. At the time I put this down to the dominance of American organisations like Ford and GM. Ford was later a key player in the automotive industry's conversion to Isometric.
Established industries with a large quantity of infrastructure - like railways and utilities - were slow to change fastener standards due to issues of backwards compatibility with whatever already existed. The automotive industry was more agile in comparison and could change fastener standards whenever a new model or vehicle platform was designed.

2. I believe that the smallest Whitworth size was 1/8 inch. I came across this size in domestic appliances but it was rarely found in the industrial environment, where the BA series was more popular for fasteners of this size. Whitworth sizes were popular from 3/16 inch upwards.
Whitworth fasteners are available in 3/16 and 1/8 inch. There is also 5/32 inch but this is long obsolete except as a Meccano fastener. BSF fasteners are available in 7/32 and 3/16 inch. There was a general rule in industry that Whitworth and BSF fasteners smaller than 1/4 inch were used on heavier mechanical assemblies or those using a significant number of larger Whitworth and BSF fasteners, and larger BA fasteners were used on electrical and precision mechanical assemblies or those using a significant number of smaller BA fasteners.
4. I have long thought that a lot of obsolete stuff, surplus to industry's requirement, gets dumped on the home DIY market. The move from Whitworth to Isometric was somewhat sporadic, with Unified occasionally getting in the way. I remember once around 1975 in a hardware store, asking for some Isometric fasteners, and being told, rather pompously, "They will never catch on for years yet." Six months later, the  same shop was selling almost exclusively Isometric
During the 1950s, 60s, and 70s most medium sized towns had at least one industrial surplus shop selling electrical and mechanical components. It was commonplace for owners of smaller independent DIY and hardware shops to prowl them and stock up with items being sold at a lower price than the manufacturer's prices. That resulted in Whitworth / BSF, and some Unified, fasteners ending up on the DIY market many years after industry had moved over to metric fasteners. The larger DIY chains like B&Q and Wickes bought new merchandise so there was probably a time when they were selling mostly metric fasteners whilst smaller independent DIY and hardware shops were mostly selling Whitworth fasteners.

Re: UNC and UNF fasteners in Britain

Posted by Denis McMahon on Jul 15, 2019 7:20 pm

Thanks, Arran, for the clarification on Whitworth fasteners. I vaguely remember 5/16 Whitworth on domestic appliances, but was not sure.

As a lad I had many happy hours with Meccano. I built, among other things, cranes, steerable motor cars, a transporter bridge (two examples still working in the UK as far as I know), and a loom which actually worked. I took it to school and my teacher was most impressed!  Happy days!
Denis McMahon, BSc, MIET, MBCS, PGCE

Re: UNC and UNF fasteners in Britain

Posted by Roy Bowdler on Jul 16, 2019 8:53 am

Denis, I was slow to pick up on your CEGB comment, but an advertisement in an E&T on-line email that I received recently for The Uniper Academy reminded me of its heritage. http://www.cegbmidreg.co.uk/ptc/leaflet/ptccover.htm

I trained at the Plant Training Centre as an Apprentice and returned some year later as an Instructor/Training Officer, before moving to Whitehall Road Leeds (North East Region) to head up the Electrical Department there.  Post-privatisation Powergen moved the Plant  Training Centre a few miles from Drakelow to Ratcliffe on Soar, whereas National Power went from Leeds, to Bricket Wood, to Didcot, to Ferrybridge within 5 years. Redundancy seemed a more attractive option in the end!  Incidentally my successor at Drakelow ended up at National Grid and as far as I know is still there.      

 

Re: UNC and UNF fasteners in Britain

Posted by Arran Cameron on Jul 16, 2019 12:42 pm

Denis McMahon:
My first experience of Isometric fasteners in industry was in 1973 when I worked for a while for a subsidiary of Philips.

There are differences between the head sizes for ISO / ANSI metric fasteners and DIN metric fasteners. There are also JIS metric fasteners with small heads.

ISO / ANSI metric
M10 16mm
M12 18mm
M14 21mm

DIN metric
M10 17mm
M12 19mm
M14 22mm

DIN metric head sizes are more common although I have encountered ISO / ANSI metric on cars built since the late 1990s. The DIN metric sizes includes M7 with an 11mm head, so beloved by the French that no French car is complete without one, but nobody outside of France uses them. A 7/16 inch AF spanner also fits them.

JIS metric
M8 12mm
M10 14mm
M12 17mm
M14 19mm
M16 22mm

A 14mm head is also found on some M10 fasteners with a fine thread.

 

 

Re: UNC and UNF fasteners in Britain

Posted by Denis McMahon on Jul 18, 2019 9:03 pm

Roy Bowdler:
Denis, I was slow to pick up on your CEGB comment, but an advertisement in an E&T on-line email that I received recently for The Uniper Academy reminded me of its heritage. http://www.cegbmidreg.co.uk/ptc/leaflet/ptccover.htm

I trained at the Plant Training Centre as an Apprentice and returned some year later as an Instructor/Training Officer, before moving to Whitehall Road Leeds (North East Region) to head up the Electrical Department there. . .

 

 
Thanks Roy for that interesting link about the training centre at Drakelow. I was based in the North Eastern Region and was posted to various power stations there at various times. There was a training centre at Stella South power station, now gone, but the one you describe at Drakelow was certainly on a much bigger scale. I never visited Drakelow but I recall that from the railway there was an ash silo visible, which I believe could be something to do with Drakelow. I left the CEGB to do a degree.
Denis McMahon, BSc, MIET, MBCS, PGCE

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