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#650500 - 04/28/16 7:20 am Need a Tutorial on British Threads and Hardware  
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Mr Bentwrench Offline
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Louisville, KY USA
I've done British for a long time but am confused on the time line of British threads and hardware. I started with the completely oddball Whitworths on a 1954 MGTF and learned about BSC & BSF on later MGBs. Then, my wife's '74 Ford Mustang II had more metric than my new '79 MGB with mostly SAE! Wife's '95 Triumph Thunderbird is all metric. Now I have a '67 BSA A65T up on my lift (with a '75 Trident coming in next week) and I'm just never quite sure what wrench or socket to grab because it's always the wrong one. Know the feeling? wink

My topic is what is the time line on British hardware? What came before before Whitworth? Wooden pegs? At approximately what year did Whitworth begin to phase out and was it then replaced by BSC/BSF? Any clue on BSP? Who and when did they begin to change over to metric? Should there be any original SAE anywhere on a British motorcycle?

Any opinions on using non-standard replacements? For example, rather than ordering and waiting for the 'correct' $4.22 whitworth bolt, washer and nut for a fender strut, the alternative of a 10min trip to the hardware store for an 80cent SAE set is hard to ignore.

Last edited by Mr Bentwrench; 04/28/16 7:34 am.

My 1967 BSA A65T Thunderbolt parts bike rebuild project is kicking my ass. (wife's '75 T160 on deck)
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#650503 - 04/28/16 7:48 am Re: Need a Tutorial on British Threads and Hardware [Re: Mr Bentwrench]  
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kommando Online content
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Whitworth threads are rare on Brit bikes, the bolt heads are Whitworth sized but the threads are mainly cycle and BSF (British Standard Fine).

#650507 - 04/28/16 8:23 am Re: Need a Tutorial on British Threads and Hardware [Re: kommando]  
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REALLY? So you're saying its just a Whit head but without the bastard 55deg true Whitworth threads? Probably should get a set of new thread guages to be sure for each huh? Now I can easily substitute these 'fake Whitworths' with more common BSF? GTFO!:)

Q: What is 'cycle'? Jeez. Is that another type I never even heard of?


My 1967 BSA A65T Thunderbolt parts bike rebuild project is kicking my ass. (wife's '75 T160 on deck)
#650509 - 04/28/16 8:34 am Re: Need a Tutorial on British Threads and Hardware [Re: Mr Bentwrench]  
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There are three aspects with nuts and bolts 1. Thread form 2. Thread angle 3. Pitch or threads per inch.
Historically there has been very little standardization with British vehicles over the years up until the 1990's. If one considers motorcycle use, Usually BA form is used for small nuts and screws, Then either CEI or BSC for most nuts and bolts (until the 1960's) and these can use, for the larger sizes, either 20 or 26 TPI although most nuts and bolts use 26TPI. BSF, Whitworth, UNF, UNC, ANC thread forms have been used for various applications used but mainly in later built machines.
Just get yourself a good set of thread gauges a Zeus fastener book and take it from there. Don't forget there are different thread forms for Metric (not only the Course and fine of later years) but some strange pitches used especially if you are working on pre 1930's continental bikes.

If it is just spanner sizes you are having problem with the list below should be of use.

Across Flat Dimensions of Hex Headed Bolts
Shaft Diameter Maximum Minimum
Inches mm Inches mm
10BA 0.117 2.97 0.114 2.90
SAE NO 2 0.125 3.18 0.120 3.05
9BA 0.131 3.33 0.128 3.25
8BA 0.152 3.86 0.149 3.79
7BA 0.172 4.37 0.169 4.29
SAE NO 3 0.187 4.75 0.181 4.59
SAE NO 4 0.187 4.75 0.181 4.59
SAE NO 5 0.187 4.75 0.181 4.59
6BA 0.193 4.90 0.189 4.80
5BA 0.220 5.59 0.216 5.49
BS 1/8" 0.220 5.59 0.216 5.49
4BA 0.248 6.30 0.243 6.17
BS 5/32" 0.245 6.30 0.243 6.17
SAE NO 6 0.250 6.35 0.244 6.20
SAE NO 8 0.250 6.35 0.244 6.20
3BA 0.282 7.16 0.277 7.04
SAE NO 10 0.312 7.92 0.305 7.75
SAE NO 12 0.312 7.92 0.305 7.75
5mm 0.315 8.00 0.300 7.64
2BA 0.324 8.23 0.319 8.10
BS 3/16" 0.324 8.23 0.319 8.10
1BA 0.365 9.27 0.360 9.14
6mm 0.394 10.00 0.379 9.64
0BA 0.413 10.49 0.408 10.36
SAE 1/4" 0.438 11.13 0.425 10.80
BS 1/4" 0.445 11.30 0.435 11.05
SAE 5/16" 0.500 12.70 0.484 12.29
8mm 0.512 13.00 0.495 12.57
BS 5/16" 0.525 13.34 0.515 13.08
SAE 3/8" 0.563 14.30 0.544 13.82
BS 3/8" 0.600 15.24 0.585 14.86
SAE 7/16" 0.625 15.87 0.603 15.32
10mm 0.669 17.00 0.652 16.57
BS 7/16" 0.710 18.03 0.695 17.65
12mm 0.748 19.00 0.727 18.48
SAE 1/2" 0.750 19.05 0.725 18.42
SAE 9/16" 0.812 20.62 0.798 20.27
BS 1/2" 0.820 20.82 0.800 20.32
BS 9/16" 0.920 23.37 0.900 22.86
SAE 5/8" 0.938 23.81 0.906 23.01
16mm 0.945 24.00 0.912 23.16
BS 5/8" 1.010 25.65 0.985 25.02
SAE 3/4" 1.125 28.58 1.088 27.64
20mm 1.181 30.00 1.148 29.16
BS 3/4" 1.200 30.48 1.175 29.85
BS 7/8" 1.300 33.02 1.270 32.26
SAE 7/8" 1.313 33.34 1.269 32.23
24mm 1.417 36.00 1.378 35.00
BS 1" 1.480 37.59 1.450 36.83
SAE 1" 1.500 38.10 1.450 36.83

#650511 - 04/28/16 9:28 am Re: Need a Tutorial on British Threads and Hardware [Re: Mr Bentwrench]  
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MR Whitworth was the first guy ( in the 1840's) to decide that a national system was needed.
Before that, companies just made their own, random thread pitches.


http://stainlessbits.com/link12.html

is useful but a few are wrong, especially as you get into the BA sizes.

#650517 - 04/28/16 10:12 am Re: Need a Tutorial on British Threads and Hardware [Re: Mr Bentwrench]  
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Originally Posted By Mr Bentwrench
I've done British for a long time but am confused on the time line of British threads and hardware. I started with the completely oddball Whitworths on a 1954 MGTF and learned about BSC & BSF on later MGBs.


It's only "oddball" if you don't understand it, and remember that any "inch" size thread will now be considered oddball by around nine-tenths of the world's population!

http://www.enginehistory.org/british_fasteners.shtml

Originally Posted By Mr Bentwrench
At approximately what year did Whitworth begin to phase out and was it then replaced by BSC/BSF?


It's not a case of one phasing out another.

Whitworth (later also known as BSW) is a coarse thread, BSC is a fine thread (originally adopted for bicycles under the name CEI) and BSF is a medium-fine thread.
Not all British Standard threads use the "Whitworth" 55 degree thread form (CEI/BSC for instance, is 60 degree, BA is 47.5).


Originally Posted By Mr Bentwrench
Any clue on BSP?


British Standard Pipe thread.

http://www.britishfasteners.com/threads/bsp.html


Originally Posted By Mr Bentwrench
Who and when did they begin to change over to metric?


Depends who you mean. The change to metric at least for British motorcycles occurred after the closure of the old BSA, Triumph and Norton factories.


Originally Posted By Mr Bentwrench
Should there be any original SAE anywhere on a British motorcycle?


'Unified' (UNF, UNC, etc.)?
Yes.

https://en.wikipedia.org/wiki/United_States_Standard_thread

Quote:
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 National Coarse) to describe a fastener that previously would have been designated USS and the Unified Thread Standard uses the term UNF (Unified National Fine) to describe a fastener that would have previously been designated SAE.


http://www.ring-plug-thread-gages.com/ti-N-vs-UN.htm

Quote:
The “UN” thread form was developed after World War II by representatives of Great Britain, Canada, and the United States of America, to prevent recurrence of the wartime difficulties in supplying fasteners and tools in both British Standard Whitworth and US Standard configurations when and where needed. In 1949, after years of committee meetings between Canada, England and United States of America the American National Standard Series was replaced with the Unified Inch Standard Series.



BSA and Triumph (and to a lesser extent Norton) began the change-over to Unified threads during the late '60s. BSA and Triumph accomplished this somewhat faster than Norton who never did fully complete change to Unified threads before the closure of NVT.

Originally Posted By Mr Bentwrench
Any opinions on using non-standard replacements? For example, rather than ordering and waiting for the 'correct' $4.22 whitworth bolt, washer and nut for a fender strut, the alternative of a 10min trip to the hardware store for an 80cent SAE set is hard to ignore.


The vast majority of fasteners on a T160 (and other Triumphs produced from approximately 1968 on) will be Unified, and you shouldn't find any actual 'Whitworth' fasteners as coarse threads on a T160 will be UNC and fine threads are mostly UNF but there are a still few BSF, BSC & BA (carbs), BSP (fuel taps).

http://www.britishfasteners.com/threads/index.html

http://www.sat.dundee.ac.uk/~psc/spanner_jaw.html#Jaw_Size_Table

The T160 parts book identifies many threads (as "UNF", "UNC" etc.)
http://www.classicbike.biz/Triumph/Parts/Trident/1975T160PartsManual.pdf



Last edited by L.A.B.; 04/28/16 12:04 pm.
#650537 - 04/28/16 2:00 pm Re: Need a Tutorial on British Threads and Hardware [Re: Mr Bentwrench]  
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Hi,

Originally Posted By kommando
Whitworth threads are rare on Brit bikes, the bolt heads are Whitworth sized but the threads are mainly cycle and BSF (British Standard Fine).

Mmmm ... yes and no.

Out of the Whitworth standard came a standard hex. size for each fastener major diameter - e.g. 1/4"W had a 0.525"AF head, 5/16"W had a 0.600"AF head, 3/8"W had a 0.710"AF head, etc.

In principle, this isn't any different to, say, Unified/SAE (e.g. 1/4"UNF/UNC has a 7/16"AF head, 5/16"UN has a 1/2"AF head, 3/8"UN has a 9/16"AF head, etc.), ISO metric (e.g. M6 has a 10 mm. AF head, M8 has a 13 mm. AF head, M10 has a 17 mm. AF head, etc.), etc.

What confuses the hell out of newbies to the British system is, starting with the introduction of BSF (1913?), a given thread major diameter had a smaller hex. AF than the same Whitworth major diameter but, so that Whitworth tools could continue to be used, to aid adoption of the new threadform, the "smaller hex. AF" was the next-smaller Whitworth AF; i.e. 1/4"BSF has a 0.445"AF head (same as 3/16"W), 5/16"BSF has the 0.525"AF head, 3/8"BSF has the 0.600"AF head, etc.

With the the adoption of other then-commonly-used threadforms to a specific British Standard (e.g. "Cycle" was originally specified by the Cycle Engineering Institute but became BSC - British Standard Cycle), the smaller-hex.-size-for-a-given-major-diameter became the norm.

Fast-forward to the late-1950's/early 1960's and, as BSA and Triumph are developing their new unit models, BSA (as Triumph's parent) adopts BSC, BSF and BA threadforms as standard, as do its outside component suppliers.

That's why you find a lot of sockets and wrenches marked with a one "BS"-suffixed fraction and the next-smaller fraction suffixed "W" - e.g. 3/8"BS 5/16"W - because both major diameters use the same hex. AF

Finally, just to put the tin lid on newbie confusion:- whistle

. While I haven't seen many actual brand-new Whitworth-thread fasteners, any that I have seen in the thick end of the last thirty years have had the smaller BS hex. AF, rather than the old, larger Whitworth hex. (this is probably unsurprising given that "Whitworth" had (has?) a British Standard - BSW - and afaik old British vehicle owners as a group have been the largest buyers of all BS-thread fasteners for many years).

. You haven't got to 'small hex.' fasteners yet ... laughing which were available as standard from industrial fastener suppliers and certainly were used profusely by both Triumph and BSA in the 1960's ...

So, while you can think of the fasteners on your Thunderbolt as having "Whitworth heads" if that's really what floats your boat, the threads they're on are all British Standard and, each thread you look at, the major diameter will match the "BS" fraction on the tool that fits, bigt not the "W" fraction. frown

Originally Posted By Mr Bentwrench
you're saying its just a Whit head but without the bastard 55deg true Whitworth threads? Probably should get a set of new thread guages to be sure for each

Ime, the difference between 55 degrees and 60 degrees, even if it's visible (with a magnifying glass), is irrelevant in use:-

. You cannot buy real 1/4"BSF fasteners, they're all Cycle (BSC). Because, while the threads are 55 degrees and 60 degrees respectively, the threads-per-inch are the same (26 tpi).

. I've used BSB (British Standard Brass, 55 degrees) and BSC (Cycle, 60 degrees) interchangeably when the they're 26 tpi.

Originally Posted By Mr Bentwrench
Now I can easily substitute these 'fake Whitworths' with more common BSF?

Nope. As I say, on your Thunderbolt, the fastener threads and heads are British Standard - BSC (Cycle) and BSF. But, apart from 1/4" major diameter, the threads-per-inch are different - BSC (Cycle) threads chart, BSF threads chart.

T160
Thankfully, because Small Heath prepared the parts book (rather than Meriden), fastener part descriptions tend to have Small Heath's level of detail, although there are enough missing or incorrect to be frustrating. frown Over the years, I've replaced nearly all the fasteners on my T160's with stainless; the "StainlessBits/link12" spreadsheet, a micrometer (to measure diameters accurately) and a set of thread gauges (aka 'screwpitch gauges') all help(ed) to pick up more errors before stainless was ordered but the most useful has been a 2BA, 10-32 and M5 screw and nut in three labelled resealable bags.

"StainlessBits/link12" and thread gauges both become inaccurate around 3/16" major diameter, the only way to be sure between BA and Unified (and pattern metric) threads is to actually fit screws or nuts to the female or male thread.

Hth.

Regards,

#650742 - 04/30/16 6:26 am Re: Need a Tutorial on British Threads and Hardware [Re: Mr Bentwrench]  
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Hi Stuart. Been following your other, similar thread on the RAT forum. I was laboring under the impression that I was at least a little clued up on the subject. You pissed all over my Cornflakes!

Been interesting reading though and thanks for the clarification.

Cheers
Rod

#650830 - 04/30/16 10:36 pm Re: Need a Tutorial on British Threads and Hardware [Re: Mr Bentwrench]  
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"My 1967 BSA A65T Thunderbolt parts bike rebuild project is kicking my ass."

I know about 2 percent of everything that's been written above, but if this is all about your '67 Tbolt, I can make it quite simple.

Most of the hardware on your bike, the engine in particular, is 1/4" X 26 tpi, 5/16" X 26 tpi, and 3/8" X 26 tpi, with BS heads. I'm admittedly clueless about the smaller stuff like fuel tank badge screws; luckily I haven't had to deal with much of that.

Some of the chassis hardware is "Unified", which carries the same thread densities as SAE. However, the thread forms are slightly different. One example is the right-side footpeg stud. I was able to use an SAE stud there, but I had to run a SAE tap through the threads first.

My best advice is to get with British Tools and Fasteners and order up a set of British thread gauges. You can also order hardware from them by spec. It's generally cheaper than ordering by part number from a BSA parts supplier, and much is available in stainless.

Unless you're a stickler for originality, I would say, anywhere there's a through bolt with a nut on the end, replace it with SAE stainless steel. I love stainless - I dislike polishing and I hate rust. Also, you can cut stainless bolts to length if needed and not have to worry about the ends rusting.


Mark Z

'65(lower)/'66(upper, wheels, front end, controls)/'67(seat, exhaust, fuel tank, headlamp)/'70(frame) A65 Bitsa.
#650844 - 05/01/16 3:19 am Re: Need a Tutorial on British Threads and Hardware [Re: R Moulding]  
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Hi Rod,

Pleased to be of help. smile Sometimes I think my head's like a bend in a river - every now-and-then a flash-flood deposits a load of rubbish there; later, I find stuff that's useful to other people. laughing I am lucky that this country at least used to have decent reference libraries, where you could look up arcane stuff like old British Standards (now, in the internet age, the BSI's worked out this stuff is worth money, while libraries are closing because "it's all on the internet" crazy ).

Regards,

#650901 - 05/01/16 12:06 pm Re: Need a Tutorial on British Threads and Hardware [Re: Mr Bentwrench]  
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All of this has been a tremendous help. It's been almost 30 years since I did my '54 MG-TF and thank God I still have a good set of tools. I just forgot how to use them! smile

I posted this topic for a number of reasons. Primarily, my '67 A65 rusty parts bike reclaimation was forcing me to relearn the British fastener system and all the contributions here have really created quite a body of knowledge for others' future search reference. Thanks to all that really put in the time and effort to create it.

Second, it would also give me a leg up on my upcoming T-160 project on deck.

Third, and I'm about half embarrased to admit it here is, I write a monthly tounge-in-cheek tech article for our British Sports Car Club called "Ask Mr Bentwrench". (Boy, THAT'S scary!) My topic for June was going to be about the British fastener system based upon what I knew and now (more correctly) learned here. Its all starting to sink in and make sense and really isn't all THAT hard to understand if you just study it and learn it. Odd but I really LIKE the fine details of obscure tech. smile


My 1967 BSA A65T Thunderbolt parts bike rebuild project is kicking my ass. (wife's '75 T160 on deck)
#650902 - 05/01/16 12:15 pm Re: Need a Tutorial on British Threads and Hardware [Re: Mark Z]  
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Originally Posted By Mark Z
"My 1967 BSA A65T Thunderbolt parts bike rebuild project is kicking my ass."

I know about 2 percent of everything that's been written above, but if this is all about your '67 Tbolt, I can make it quite simple.

Most of the hardware on your bike, the engine in particular, is 1/4" X 26 tpi, 5/16" X 26 tpi, and 3/8" X 26 tpi, with BS heads.

Some of the chassis hardware is "Unified", which carries the same thread densities as SAE. However, the thread forms are slightly different. One example is the right-side footpeg stud. I was able to use an SAE stud there, but I had to run a SAE tap through the threads first.

Unless you're a stickler for originality, I would say, anywhere there's a through bolt with a nut on the end, replace it with SAE stainless steel. I love stainless - I dislike polishing and I hate rust.


Thanks Mark Z. That was spot on and especially for my task today, removing the rusty stripped heads for the timing side cover and reconditioning the rusted up points and advance assembly. I feel a hardware parts order coming on by days end. wink


My 1967 BSA A65T Thunderbolt parts bike rebuild project is kicking my ass. (wife's '75 T160 on deck)
#650952 - 05/01/16 5:15 pm Re: Need a Tutorial on British Threads and Hardware [Re: Mark Z]  
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Originally Posted By Mark Z
Some of the chassis hardware is "Unified", which carries the same thread densities as SAE. However, the thread forms are slightly different. One example is the right-side footpeg stud. I was able to use an SAE stud there, but I had to run a SAE tap through the threads first.


http://www.smithy.com/machining-handbook/chapter-3/page/24

Quote:
THREAD FIT AND CLASSIFICATIONS

The Unified and American (National) thread forms designate classifications for fit to ensure that mated threaded parts fit to the tolerances specified. The unified screw thread form specifies several classes of threads which are Classes 1A, 2A, and 3A for screws or external threaded parts, and 1B, 2B, and 3B for nuts or internal threaded parts. Classes 1 A and 1 B are for a loose fit where quick assembly and rapid production are important and shake or play is not objectionable. Classes 2A and 2B provide a small amount of play to prevent galling and seizure in assembly and use. and sufficient clearance for some plating. Classes 2A and 2B are recommended for standard practice in making commercial screws. bolts. and nuts. Classes 3A and 3B have no allowance and 75 percent of the tolerance of Classes 2A and 2B A screw and nut in this class may vary from a fit having no play to one with a small amount of play. Only high grade products are held to Class 3 specifications.


https://sizes.com/tools/thread_ncnf.htm
Quote:

NC, NF, NEF
to one inch in diameter

These thread series are obsolete, having been replaced by the Unified thread series.


https://sizes.com/tools/thread_american.htm
Quote:
UNC, UNF, UNEF, UNS
screw thread gauges to 1 inch in diameter


These series (and the UNR, UNJ and fixed-pitch series) are the inch-based thread series currently used in the United States, and have been since 1949.¹ They superceded the American National Series (NC, NF, etc.)


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.

#650987 - 05/01/16 11:25 pm Re: Need a Tutorial on British Threads and Hardware [Re: Mr Bentwrench]  
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"removing the rusty stripped heads for the timing side cover..."

Stainless steel socket-head outer timing cover and primary cover screws are available in sets from many BSA parts suppliers. Again, not original-looking, but much easier to deal with.


Mark Z

'65(lower)/'66(upper, wheels, front end, controls)/'67(seat, exhaust, fuel tank, headlamp)/'70(frame) A65 Bitsa.
#651128 - 05/02/16 8:07 pm Re: Need a Tutorial on British Threads and Hardware [Re: Mr Bentwrench]  
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Something useful to use with assorted types of nut and bolts and thread standards are these type of bolt gauges and thread gauges.



Just poking the bolt into the gauge holes to figure out if they are metric or british standard or american standard sized can be very helpful.
And using the thread gauges to count the tpi (threads per inch) then narrows down what a particular bolt is.
hopethishelps.

#651160 - 05/03/16 7:13 am Re: Need a Tutorial on British Threads and Hardware [Re: Mr Bentwrench]  
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gavin eisler  Online Content
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argyll. scotland, uk
Essential reading, Zeus book
https://www.amazon.co.uk/workshop-decimal-equivalents-details-clearance/dp/B00C77BX46
Even better
with a lot more than you need for just screw threads, The Model Engineers handbook, by Tubal Cain.

https://www.amazon.co.uk/Model-Engineers-Handbook-Tubal-Cain/dp/1854861344

There are other consumers of BSF and Whitworth out there, any industrial plant from the 60s , theres still some about, although generally with full nut/ bolt head sizes, .

It helps to understand that many two wheeled bike threads originated from the bicycle. Hence the use of cycle threads for various applications, these finer threads are less prone to loosening from vibration. That is why true Whitworth , the coarsest of normal screw threads is seldom found on old brit motorcycles. Cycle threads are seldom used for threading alloy , its too fine, BSF is much more common, post 71 its UNC ( a much stronger but coarser thread)

It also helps to think of thread types for various zones of the bike.

Carb screws , control levers and electrics, BA threads.

Up to late 60s , wheel spindles steering head nuts , Cycle ( maybe).

Screws into alloy, up to late 60 s BSF ( Cycle is too fine to grip ally).

Most 1/4 fasteners , will be either 1/4 BSF or Cycle ( both 26 tpi), until late 60s, then UNF.

Some weirdo threads were still being used, 17/64 " was the thread OD for kicker cotters ( originally, not any more)
and BSA had a thing for 7/16" mounting bolts , both sizes being obsolete ish in industry which was trying to lose all the pernickity mid sizes and stick to, 3/16, 1/4, 5/16, 3/8, 1/2" as standards.

By 1971 threads are a car crash, my A65 has mostly UNC 1/4 screws for the motor, but the two rocker cover centre fasteners are BSF?, got missed off the drawing maybe. UNF, UNC, BSF , Cycle, BA , BSP , and Metric, all present in one way or another.


71 Devimead A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
#651163 - 05/03/16 7:42 am Re: Need a Tutorial on British Threads and Hardware [Re: Mr Bentwrench]  
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Mr Bentwrench Offline
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Mr Bentwrench  Offline
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Louisville, KY USA
Yeah, I really need a good universal bolt gauge. Mine sucks.

Just a few follow up questions for general clarifications:

> As a quick 'spotters guide', fair to say the BSW looks and functions very much like our UNC(course) and the BSF looks and functions very much like our UNF (fine)?

> Was there an original 'W' with a large hex head? Was this 'W' hex head reduced in size to conform with the A/F size of the BSF and THEN termed 'BSW'?

> As above, WHEN was the advent of dual marked spanners? (1/4BSW-5/16BSF) Pre-war or post-war? (thinking pre-war cars and bikes)

> How about bolt grade? Our UNC/UNF have shear grades like 3, 5 & 8. What is the grade of a common steel BSW or BSF? Are they offered in higher grades for engines and powertranes? (perhaps the 60* 26 TPI BSC/CEI is considered strong enough?)

> Although the BA is generally considered obsolete, is it still common to find them on our British carbs, linkage and even inside Lucas electric components?


My 1967 BSA A65T Thunderbolt parts bike rebuild project is kicking my ass. (wife's '75 T160 on deck)
#651174 - 05/03/16 9:37 am Re: Need a Tutorial on British Threads and Hardware [Re: Mr Bentwrench]  
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Posts: 3,405
gavin eisler Online content
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gavin eisler  Online Content
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Joined: Aug 2001
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argyll. scotland, uk
> As a quick 'spotters guide', fair to say the BSW looks and functions very much like our UNC(course) and the BSF looks and functions very much like our UNF (fine)?

Yes, they fulfill similar roles.

> Was there an original 'W' with a large hex head? Was this 'W' hex head reduced in size to conform with the A/F size of the BSF and THEN termed 'BSW'?

Pre war whitworth bolt heads were a size bigger, to save steel all bolt head sizes were reduced to the BSF hex sizes, so yes there once was a W size but its mostly on steam equipment from a bygone era. You only need the BSF sizes. sadly folks over the pond are obsessed with calling imperial threads Whitworth, this just causes confusion.
True Whitworth exists in a few rare applications still, Camera to tripod mount screws, still std 1/4 Whit. and BSP is a pipe thread form which uses Whitworth angles and pitches for a good part of the range, the worlds plumbing resists metrication to this day. It is a very strong thread ideal for massive constructions like power stations, not good at all for motorcycles.
Note the scrawl above



> As above, WHEN was the advent of dual marked spanners? (1/4BSW-5/16BSF) Pre-war or post-war? (thinking pre-war cars and bikes).

The explanation above covers this.

> How about bolt grade? Our UNC/UNF have shear grades like 3, 5 & 8. What is the grade of a common steel BSW or BSF? Are they offered in higher grades for engines and powertranes? (perhaps the 60* 26 TPI BSC/CEI is considered strong enough?)

Depends on the manufacturer, different classes of fit exist, as do different grades of steel. GKN, or Holochrome used to be good as brand name manufacturers, nowadays quality is a lottery, buy from reputable fastener specialists..

A great deal of your bikes fasteners are "special" ie, certain shank length, radiused head, or reduced hex, nuts arent so complicated, but half nuts are used in many situations . So just buying a selection box doesnt cover all the possibilities.


> Although the BA is generally considered obsolete, is it still common to find them on our British carbs, linkage and even inside Lucas electric components?

Yes, control lever clamps, pivots screws,Twistgrip clamp screws, carb screws on AMAL and doherty equipment.
Some older Lucas stuff yes, they did go metric eventually. For me metric electrics is a no brainer , starts with the battery terminals and ends with the Spark plugs, why not in between.

Last edited by gavin eisler; 05/03/16 9:47 am.

71 Devimead A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
#651181 - 05/03/16 10:00 am Re: Need a Tutorial on British Threads and Hardware [Re: Mr Bentwrench]  
Joined: Mar 2006
Posts: 3,469
L.A.B. Online content
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L.A.B.  Online Content
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Joined: Mar 2006
Posts: 3,469
Norfolk, UK
Originally Posted By Mr Bentwrench
How about bolt grade? Our UNC/UNF have shear grades like 3, 5 & 8. What is the grade of a common steel BSW or BSF? Are they offered in higher grades for engines and powertranes? (perhaps the 60* 26 TPI BSC/CEI is considered strong enough?)



http://www.fastenerdata.co.uk/10n-tensile-strength/

BRITISH INCH


#651194 - 05/03/16 11:44 am Re: Need a Tutorial on British Threads and Hardware [Re: Mr Bentwrench]  
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Stuart Online content
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Stuart  Online Content
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Scotland
Hi,

Originally Posted By Mr Bentwrench
I really need a good universal bolt gauge.

Ime, I wouldn't waste your money. With at least one British bike and one Japanese bike at the same time since 1979, I've never needed a bolt gauge - by definition, it cannot tell you the difference between Imperial threads (because the shanks are the same diameter), and most of the metric diameters are so close to Imperial ones that simply having some sort of clearance to be able to insert a bolt of a given diameter negates its ability to tell the difference between Imperial and metric. Ime, it's quicker to use the micrometer/calipers/steel rule that you use for measuring everything else.

Originally Posted By Mr Bentwrench
fair to say the BSW looks and functions very much like our UNC(course) and the BSF looks and functions very much like our UNF (fine)?

Ime, no. On your T160, all(?) threads into steel are UNF; on your Thunderbolt, they're Cycle (aka CEI and BSC). Otoh, on your T160, most threads into aluminium alloy are UNC; on your Thunderbolt, they're BSF. However, the operative word is "most"; e.g. the T160's tacho. drive mounting bolt thread is UNF (left-hand), although it's screwed into the ally of the crankcase; the front disc caliper studs are BSF into ally; any pre-'69 650 Triumph has a Cycle-thread bolt screwed into the front of the ally timing cover. Etc., etc.; the list of exceptions is almost endless.

You'll simply never, ever come across Whitworth/BSW unless you plan to venture into owning a pre-unit or a Notrun (or 1960's industrial plant); imho I really wouldn't concern myself with the minutiae of Whitworth/BSW while still struggling to get my head around BSF, Cycle and Unified.

Originally Posted By Mr Bentwrench
Although the BA is generally considered obsolete, is it still common to find them on our British carbs, linkage and even inside Lucas electric components?

When our motorcycles were new, the fastener/component threads used weren't "obsolete",that's why they were used. Now, our complete motorcycles are "obsolete" but the parts we buy for them are made by an industry geared to supplying our requirements, or we wouldn't buy their products. Hence, we can't go to a fastener retailer and buy parts for our motorcycles, but a specialist retailer is specialist because he supplies parts that fit our motorcycles. So by-and-large, "British carbs, linkage and even inside Lucas electric components" have whatever threads - "obsolete" or not is irrelevant - are needed to mount the new parts to our motorcycles.

Originally Posted By Mr Bentwrench
WHEN was the advent of dual marked spanners? (1/4BSW-5/16BSF) Pre-war or post-war? (thinking pre-war cars and bikes)

Afaik, the one-size-smaller-hex. head was introduced with BSF in 1908(?), so anytime after that?

Originally Posted By Mr Bentwrench
How about bolt grade? Our UNC/UNF have shear grades like 3, 5 & 8. What is the grade of a common steel BSW or BSF? Are they offered in higher grades

laughing In some thirty years concerning myself with the minutiae of Imperial-thread fasteners in GB, every non-Britbike specialist fastener retailer has closed, even in a city like London. Afaik, even in GB, there are two categories of Imperial fastener supplier - stainless steel fastener retailers and Britbike parts retailers. The specific stainless retailer I use - Dave & Richard Middleton - make their own Imperial fasteners so could advise the stainless grade they used for a particular fastener; otoh, I can't think of any Britbike parts retailer whom I'd even bother asking the grade of a particular fastener.

It isn't impossible that a retailer still survives in either GB or the US that sells Imperial fasteners with the same thread but in different grades, and Les might well be able to supply the web address, but I really wouldn't hold my breath ... and I'd be sitting down when I read the price list ...

Originally Posted By gavin eisler
It also helps to think of thread types for various zones of the bike.

Carb screws , control levers and electrics, BA threads.

Up to late 60s , wheel spindles steering head nuts , Cycle ( maybe).

Screws into alloy, up to late 60 s BSF ( Cycle is too fine to grip ally).

Most 1/4 fasteners , will be either 1/4 BSF or Cycle ( both 26 tpi), until late 60s, then UNF.

Mmmm ... depends on your pov and experience:-

. "Carb screws , control levers and electrics, BA threads" - Mk.1 Concentric threads are a mixture of BA and Cycle, control lever pivots are Cycle or UNF, electrics depend on where Lucas made the component - e.g. I've coils with 2BA, 10UNF and M5 threads; T160 starters have both UNF and metric threads ...

. On Triumphs and BSA's, all front-end threads - including "wheel spindles steering head nuts" - change from Cycle to UNF from '69, UNC are added from '71 with the introduction of aluminium alloy components but, as I say, the '73-on disc caliper studs are BSF.

. Most "screws into alloy, up to late 60 s" are BSF. But there are odd ones - like the blanking bolt in the front edge of Triumph 650 twin timing covers - that are Cycle.

. "1/4 fasteners" were originally specified as either Cycle or BSF depending on the material (steel or ally) they screwed into; today, Cycle is supplied for both; when they were superseded, they were superseded by both UNF and UNC, again depending on the material (steel or ally) they screwed into.

Hth.

Regards,

Last edited by Stuart; 05/03/16 1:22 pm.
#651195 - 05/03/16 12:01 pm Re: Need a Tutorial on British Threads and Hardware [Re: Stuart]  
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Rohan Offline
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Rohan  Offline
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Oztralia
Originally Posted By Mr Bentwrench
I really need a good universal bolt gauge.

Originally Posted By Stuart
Ime, I wouldn't waste your money.


The white (plastic) bolt gauge I illustrated above came as a FREEBIE from my local bolt supplier - so it was good value.

Sometime back I was given many kilos of used bolts, and it has been quite useful in sizing suitable bolts for all sorts of things, where you just select something suitable looking and check what it might be. Its surprising how accurate it is...

BTW, BA is seemingly very closely based on Swiss clockmakers metric threads, and if you are into dodgy things, in many cases metric can be substituted !!. Not recommended at all...

#651201 - 05/03/16 12:24 pm Re: Need a Tutorial on British Threads and Hardware [Re: Stuart]  
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L.A.B. Online content
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L.A.B.  Online Content
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Norfolk, UK
Originally Posted By Stuart
It isn't impossible that a retailer still survives in either GB or the US that sells Imperial fasteners with the same thread but in different grades and Les might well be able to supply the web address, but I really wouldn't hold my breath ...


Doesn't seem to be too much of a problem. I found this place easily enough:

http://www.thomassmithfasteners.com/

Quote:
Materials & Mechanical Properties

We supply fasteners in a wide range of materials and grades. Materials include:

Carbon & Alloy Steel – Grades 4.6, 8.8, 10.9, 12.9, 14.9 in Metric / R, S, T, V, X in Imperial, Petrochemical L7, L7M, B7, B7M
Stainless Steel – A2, A4, B8, B8M, Super Duplex
Exotic materials including Monel & Inconel

#651202 - 05/03/16 12:32 pm Re: Need a Tutorial on British Threads and Hardware [Re: Rohan]  
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Stuart Online content
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Stuart  Online Content
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Scotland
Hi,

Originally Posted By Rohan
BA is seemingly very closely based on Swiss clockmakers metric threads,

BA is the adoption of the 1878 Swiss standard by the British Association for the Advancement of Science (hence "BA"), after the BAAS specifically considered the standardisation of small threads (Whitworth having only standarised threads 1/8" major diameter and larger). For clarity, note BA isn't "based on" the Swiss standard, it is the Swiss (Société des Arts de Genève) standard, including details like the thread 47.5-degree included angle, etc. Apart from the base - zero - being 6 mm. major diameter and 1 mm. pitch, the Swiss standard was never 'metric'; it was developed in much the same way as Whitworth developed his - collect and measure all existing threads, reverse-calculate the curves used and standardise on an average.

Hth.

Regards,

#651203 - 05/03/16 12:46 pm Re: Need a Tutorial on British Threads and Hardware [Re: Mr Bentwrench]  
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L.A.B. Online content
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L.A.B.  Online Content
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Norfolk, UK
Originally Posted By Mr Bentwrench
> As above, WHEN was the advent of dual marked spanners? (1/4BSW-5/16BSF) Pre-war or post-war? (thinking pre-war cars and bikes)


http://www.sat.dundee.ac.uk/~psc/spanner_jaw.html#Background
Quote:

During the Second World War the standards were revised again as "War Emergency B.S. 916 : 1940" as an austerity measure to reduce steel consumption and this resulted in the head sizes being reduced by one step (so the head size for the older Whitworth 1/4" bolt was used for the revised BSW/BSF 5/16" bolt, etc, avoiding the need for new tools), also bringing them closer to the size range commonly used today:


Which suggests that it would've started during WW2.

#651277 - 05/03/16 6:37 pm Re: Need a Tutorial on British Threads and Hardware [Re: L.A.B.]  
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Rohan Offline
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Rohan  Offline
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Oztralia
Originally Posted By L.A.B.

Which suggests that it would've started during WW2.


Not that this would affect motorcycles much.
Many motorcycle makers came from the ranks of the bicycle industry - and would have been geared up to produce cycle threads fasteners, along with some BSF.

Coarse whitworth threads weren't well suited to resist vibration, fine threaded fasteners are more suited to this.

I don't believe I have ever met up with a genuine large headed WHITWORTH bolt in any motorcycle I have had to do with.
Met plenty of them in old farm machinery, tractors, harvesters, ploughs etc.
Big and chunky are the words that best describe them...


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