Hi Stuart So you spotted my deliberate error, just testing. i stand corrected, the BSA Whit likeness must only be over a certain size, it certainly aplies in larger inch ish sizes. And i didnt know about the 40 tpi machine thread ,no sir, never too old to learn! Cheers Pod
71 Devimead A65 750 56 Norbsa 68 Longstroke A65 Cagiva Raptor 650 MZ TS 250 The poster formerly known as Pod
#55541 - 08/13/071:37 pmRe: British Std Whitworth????
Joined: May 2005 Posts: 146Britishtools
BritBike Forum member
IN the course of having access to 800 types of fasteners (all in one form of Brit thread or another) for engine case kits, there are many different threads associated with any one bike.
Stuart - you are right about the differences between BSP and BSW.
You are also right about the 40tpi thread. This is commonly refered to as Model Engineer thread, and typically sizes (whether 1/4", 5/16" or 1/2") come in either 32 TPI or 40 TPI.
These should not be confused with BSW, in which the 1/8" version also has 40 TPI.
In summary, I have found all of the above threads to be found in BSA, Triumph or Norton packages depending on the model and year.
Of course, 50's models mostly contained BSC (British Std. Cycle or also known as CEI, Cycle Engineers Institue).
I have found a much wider variety in the casing kits for newer models, including 2BA, BSW 3/16", BSW 1/4", BSF 3/16" and on and on. These are only the cover sets however, the entire bike (again, depending on model) will contain even greater variety.
Anyway, the key to determining most of the BSC threads is to remember that they mostly contain 26 TPI (and sometimes 20 TPI). A thread gauge for BSC is NOT available and to the best of my knowledge, never has been, unless hand made.
I used to know a guy who sold Go/No-Go gauges for BSC threads, but at $400 a pop, it seemed a little pricey for those of us who know how to count to 26.
For the rest of you non BSC fastener types....measure the shank width of your hardware. Determine its size in fractional inches (1/4, 5/16, 3/8 etc) and then count the number of threads in 1". If only a half and inch of thread is available, just multiply times 2.
This will lead to the inevitable answer! There are only so many options, even if you are a thread or two off in your count. If you measure a 3/16"- 32 then you have a BSF. Whitworth hardware with 3/16" width has 24 TPI, so not even close. BSC will have 26 TPI (mostly) so not close again.
In fact the only REAL close thread would be 2BA which has 31.36 TPI. However its major O.D. is .1850" where BSF 3/16" is .1875" so trust me, the two are closely interchangeable, although definately not recommended!
Well, my long winded point was that in most cases, your hardware can be figured out quite easily with a ruler and your eyes by simple deduction. After all, there are only 8 thread types to choose from, haha.
Originally posted by Britishtools: my long winded point was that in most cases, your hardware can be figured out quite easily with a ruler and your eyes by simple deduction. After all, there are only 8 thread types to choose from
Firstly, while I do not have any wish to denigrate your experience, which is obviously deep ("800 types of fasteners (all in one form of Brit thread or another)"), ime it does not follow that it extrapolates correctly in the wider context of all threads on a bike. By definition, the holes for case screws are in components made, or at least finished, by the bike maker, so are most likely to be to the 'house standard' of that maker (e.g. on Triumphs & BSA's, BSF into alloy on pre-1970's, Unified (usually UNC) into alloy 1968/69/70-on); otoh, the outside suppliers of components had their own 'house standards' (in the widest sense of the phrase in some cases :rolleyes: ) that might or might not accord with the standards of the bikes they were bolted on. Then some of those outside suppliers are still in business and still supplying components, but to different standards; e.g. the Lockheed components supplied new '73-on had Unified threads, but all replacements since about 1980 have metric threads; how can you tell whether that scuffed master cylinder mounting is an original or a 20-odd-year-old replacement? Then, connected with that is the fact that most components supplied by outside suppliers when the bikes were new have been patterned in the Far East for several years, or even decades, *most* threads on these pattern components are metric, but some aren't; e.g. on the Veglia-replica speedo. & tacho. that've been around for several years, if you buy the ones with the mounting studs on the bottom, these are still 0BA, which you can easily mistake for M6 if you aren't expecting it.
Thus, it makes absolutely no sense whatsoever to be, on the one hand, measuring diameters to ten-thousandths of an inch and, on the other, counting threads by eye against a steel ruler and not worrying if you're a couple of threads out. In a recent Triples On Line thread, someone wrote how he'd had to entirely strip a triple engine because he'd assumed the oil pressure switch (under the centre crankcase on a triple) was 1/8"BSP (28 tpi) when it's 1/8"NPS (27tpi) and, of course, he'd stripped the thread in the softer aluminium alloy crankcase.
Moreover, by definition, we're dealing with old bits, often corroded and/or with worn threads. When a new fastener won't fit, as the next step is likely to be clearing the corroded thread with a tap or die, you need to know *exactly* which thread you're dealing with, as choosing the wrong tap or die will simply leave you, at best, without any thread. Even a decent set of thread gauges is cheaper than a cheap micrometer, a helicoil or an engine strip.
Originally posted by Britishtools: A thread gauge for BSC is NOT available and to the best of my knowledge, never has been, unless hand made.
This might be true in the US (although I'd be surprised) but it is definitely not correct for GB - my easily-obtained thread gauge(s set) contains everything from 4tpi to 62tpi and 0.25mm to 6.0mm, including 20tpi and 26tpi.
Originally posted by Britishtools: If you measure a 3/16"- 32 then you have a BSF.
Not necessarily. On a 1970's or 1980's Triumph, if it's original, it'll be 3/16"UNF (aka No.10UNF). Otoh, as we're very likely to be dealing with pattern stuff, it could be M5 (31.8 tpi) or, as pointed out, it could be 2BA (31.4 tpi). Fwiw, you can't even tell this sort of difference *with* thread gauges; as I said in my previous post, you need labelled bags each with an appropriately-threaded nut and bolt or screw to conduct a go-nogo test. This is also true for smaller threads - on Triumphs and BSA's, the smallest I've come across are No.4UNC screws securing the air scoop screen on '68/'69/'70 tls brakes (although a lot of these will have been bu**ered by people who believe the parts books say 'self-tapping screw' :rolleyes: ) and No.4UNC screws securing the front disc brake light switch in original master cylinder mountings (M3 in the aforementioned replacements). Ime, BSA/Triumph also used No.6UNC screws to secure the pre-'71 horn/dipswitch to the handlebars (although John Healy disagrees) and No.8UNC screws to secure the tank badges on T160's (2BA on all previous models and T160 oil tank/sidepanel badges :rolleyes: ).
#55543 - 08/25/073:48 amRe: British Std Whitworth????
Joined: Aug 2001 Posts: 4,191Mark Z
BritBike Forum member
Haven't heard from '66 Enduro in a while - he must be thinking to himself "My God, what have I started?"
Fret not, '66, for most of the stuff you will be likely to replace, you will encounter only a small subset of the above. Again, get yourself a good set of British, metric, and SAE thread gauges.
As I said above, UNF carries the same thread densities as SAE, but the thread form is different. In some cases you can convert to SAE (obvious advantages if you live in the U.S.), but you may have to first chase the threads with an SAE tap (one example is lower triple tree pinch bolts).
Hi Stuart, The '73 Lockheed masters had Unified threads? All the ones I have come across have been 25 x 1 mm. That is what I make for the hydraulic clutch to match the brake side. No one has complained about the threads for the brake side replacement backshell not fitting. I would have prefered american thread. Cutting metric requires not releasing the drive nut with each pass and reversing the headstock to get back to the start. The proper way to check small diameter threads is to use three calibrated rods, one on one side and two on the other of the screw with a micrometer to measure over the rods. The Machinery Handbook gives the wire diameters and the measurements for various thread diameters/pitches. DM
#55545 - 08/25/079:54 amRe: British Std Whitworth????
Personally I have a copy of what was published in the UK as 'Machinery's Screw Thread Book' and in the USA as 'Guide to the Worlds Screw Threads' Of course olde Mr Whitworth in finding himself one morning laying outside the pub along the c**** at an angle of 55 degrees and thinking to himself 'gosh thats a good angle of dangle for a thread form' was not daft because he unlike so many others put nice radiuses at the root of the threads to reduce the stress concentrations. I believe thats why in the US they make special Whitworth form bits for the aerospace industry. Wonder if these books appear second hand on ABE BOOKS? Me I am just going for a look just for the hell of it before knocking up yet another DRY belt drive and diaphragm clutch (One finger clutch lever operation) belt system for yet another TRiumph owners club official moaning about clutch slip on his T140.......Fings I do for friends.
#55546 - 08/25/0710:13 amRe: British Std Whitworth????
Strewth , there must be enough copies of these books available on the ABE BOOKS web site so everyone can have their own copy. So open your purse if you are a Norton owner or get the wallet out if a Triumph or BSA owner.(The late Ted Bloomfield of Motor Cycle Shop in London once told me that you could tell a Norton owner by the Corker helmet , olde WW2 despatch riders coat and the money purse!!...funny how whilst BSA and Triumph owners would simply pay a bill Norton owners would often swoon as they heard it!! Mind you I suspect muttering 'discount'would of revived them!!But that was a LONG time ago when even I was sort of young.Maybe thingsa have changed.
#55547 - 09/01/0710:07 pmRe: British Std Whitworth????
Joined: Jun 2002 Posts: 9,297Stuart
BritBike Forum member
Originally posted by DMadigan: The '73 Lockheed masters had Unified threads? All the ones I have come across have been 25 x 1 mm.
You are indeed correct, for the cylinder mounting thread. However, the original mirror mounting thread is 5/16"UNF and the original brake light switch mounting thread is No.4UNC; replacements are M8 and M3 respectively.
Quite why AP mixed metric and Unified threads on the originals is a mystery ...
#55548 - 09/04/079:49 pmRe: British Std Whitworth????
Joined: Aug 2001 Posts: 918t120mike
BritBike Forum member
Strewth , there must be enough copies of these books available on the ABE BOOKS web site so everyone can have their own copy
I ordered my copy from AbeBooks.co.uk on Sunday night and it arrived today! But the choice was limited and I went for the latest (1971) that I could find, figuring that it would be late enough to catch all the metric stuff. Great tip, thanks, great site! Also settled a local argument (in my favour) that CEI is NOT Whitworth threadform a la BSW/BSF.
mike Member #: 147 1960 T120 Bonneville 1999 H*%^a VFR 800 FI V4 Triton Project (still keeping me sane (Ha-Ha!))
#55549 - 09/04/0710:48 pmRe: British Std Whitworth????
Joined: May 2005 Posts: 146Britishtools
BritBike Forum member
Thus, it makes absolutely no sense whatsoever to be, on the one hand, measuring diameters to ten-thousandths of an inch and, on the other, counting threads by eye against a steel ruler and not worrying if you're a couple of threads out.
I think we are all smart enough to agree that a person can certainly tell the differences between one fastener thread or the other in most cases. Of course there are differences! To say otherwise would be foolish. However....please do not put words in my mouth. I certainly recommend double checking ALL threads and have not suggested that people "not worry about it". I believe that I said "in most cases" you can tell the difference.
For those of you unsure about what you have. Please feel free to mail any fasteners you like directly to me and I will check the thread personally at no charge and even mail the parts back for nothing.
I have also included a link to a tapping drill chart that includes most of the discussed thread types in this topic.
Anyway...We may not be able to argue about differences in true differences between threads but the cold, hard reality is that many of the orginal fasteners (more fastener head type than thread type) are becoming scarce. I deal with Brit cycle supply shops in the UK on a daily basis and have 3 shops that hand make fasteners for me in stainless steel.
ALL OF THEM recommend using BSF 3/16" to replace 2BA hardware. Why? Because you may be able to find a pozidrive cheesehead in BSF thread and not 2BA anymore.