Extortionate Nuts and Bolts

[henry_norton]

Much has been written about BSA/Triumphs move to UNF threads in the late 60s but virtually nothing about what threads they used up to this point; BSC (cycle thread), BSF (brit std. fine), or BSW (Whitworth). I'm buggered if I know whats fitted to either of my Triumphs, (59 and 65) so I still pay 'classic motorcycle spares' prices whenever I shake one loose. Yet I've seen all the above threads for sale from engineering suppliers at 'nut and bolt' prices, which are somewhat lower.....

Are there any old school motorcycle engineers out there who can tell me what threads are holding my bikes back from shaking themselves to pieces? Cos you could save me a fortune as just about every one of my fixings is either rusty or lying in the road a few miles back. H_N

[L.A.B.]

If you know the part number/s of the fastener/s then it is generally possible to identify the thread type.

Here's a good fastener identification list for BSA/Triumph part numbers: http://stainlessbits.com/link12.html just scroll down the page until you find the relevant fastener part numbers.

There's a Norton/AMC list too:  http://stainlessbits.com/link12a.html

I believe that BSA were also known to use some of their 'own' threads at times, on their earlier (pre-Unified)machines.

[henry_norton]

Thanx L.A.B. That's an excellent resource. From the looks of it the BMI were either pure geniuses, paring down the fastener specs to an absolute minimum or were a bunch of disorganised buffoons, incapable of agreeing on one standard....! H_N

[twolitre]

For whatever my experience is worth - British pre-unified/metric usage generally used B.S.F. threads,with the odd exception of Whitworth and 'cycle' threads.  For people with no eye for thread pitch, keeping one each of 3/16, 1/4, 5/16, 3/8 and perhaps 7/16 and 1/2 inch B.S.F. for comparison, anything non-unified or metric will be 'cycle' if finer pitch and Whitworth if coarser.
  If diameter assessment is a problem, check with the jaws of an open end A/F spanner.  A 1/4 spanner has 1/4 inch jaws (Across the Flats) and so on.
  British Standard threads usually have no identifying marks.   To identify (and discard) unf items look for a circular indentation in the bolt head and a broken circle around the hole or notches on the points of the hexagon on nuts'   Metric Items generally have an '8' (or two) on bolts and nuts.
  Smaller Unified Coarse threads are the same pitch as B.S.W. and can be mixed in an emergency.  The thread angles are in fact slightly different so if mixed in an emergency a new nut and bolt should be used as soon as possible.
Jim Walker.
  OH! please don't ask about screws\and threads used on the electical equipment. THAT really is a nightmare!
  It might help to clear up another misconception.  A/F means Across the Flats (of nuts and bolt heads) and is NOT a thread size.  The matching nuts and bolts are UNIFIED not A/F.

[henry_norton]

Thanks againJim. I began a career in engineering in the 1990s so any thread that isn't metric coarse or fine looks a bit weird. As you say, a thread gauge isn't always enough to be surenas the profile can be different - a small selection of examples to check against sounds like a good idea.

Or maybe I should just buy a Honda.....H_N

[Grizzly]

Hi All

I'm not an engineer, but I am famililar with pre unit B group BSA,s

I have found that Whitworth is used into Alloy such as the primary chaincase. Mudguards etc are typicaly Cycle.

The popular Cycle sizes are 26TPI, cost a fortune especialy if you use stainless and I have found to be only avilable through specialist suppliers. 1/4 BSF is also 26TPI but the thread angle differs by some 5 degrees, something to have in mind if you mix Cycle and BSF.

One option to consider if you are not to bothered about originality is to substitute Cycle with Metric. Metric and indeed Whitworth are both available from Industrial Fastner suppliers and a lot cheaper than the specialists.

As far as spanners go I like to use Whitworh spanners and sockets on Cycle and Whitworth fastners.

Cheers

Grizzly

[henry_norton]

Cheers Grizzly - never thought of that. I don't want to start re-cutting threads in my castings but for nuts and bolts with clearance holes why not use metric? They would certainly be easier to find and cheaper, so long as the bike wasn't being entered for concours.

H_N

[Rex]

One good reason why not is that it looks so f*****g awful!
It looks like the builder/rider has no idea of engineering, but merely buys his stuff at the local B&Q; not good.
Far from being ignorant buffoons or incompetent, the users of old Imperial threadforms were actually very efficient and the threads diverse enough for any application, unlike the subsequent Unified stuff which was only adopted to enable the British manufacturers to sell in the US.  

[twolitre]

I think Grizzly missed my point when I mentioned A/F spanners.  I was suggesting using them as a handy caliper for assessing THREAD diameters.  NOT using them in place of  Whitworth/BSF spanners on the hexagons. That leads to damaged nuts and bolts AND knuckles.
  Adding metric items to a bike which is essentially built with Imperial threads not only looks wrong - it means an extra set of spanners to carry for emergencies!  Also, 6mm is not exactly 1/4 inch and 8mm is not exactly 5/16 inch.  In fact no metrics will fit your pre-drilled holes properly.
  However, Grizzly is right in saying that tapped holes in aluminium alloy castings are (usually) Whitworth.  This often applies to ferrous castings and softer metals such as brass etc.
Jim.

[henry_norton]

Rex,

"One good reason why not is that it looks so f*****g awful! "

So, just to play devils advocate here, to the untrained (or uninterested) eye, a metric hex head is only superficially different to an imperial. Does this mean the substitution of old fashioned zinc or cadmium plated parts for stainless constitute the same originality faux pas?

It's a dialemma for me right now - I have a 1959 T120 which would be quite valuable if it were restored to concours originality, but to be truly original it needs cheap, plated nuts, bolts and spokes. Yet, if I fitted it with stainless it could be devalued despite the obvious advantages. Whaddya do?

H_N

[RichP]

Most of the big jumbles have sellers with bags of 1/4" and 5/16" cycle if you don't mind cad. plated.

It is more expensive than that nasty coarse ISO metric but not silly money.

Motorcycle manufacturers were known for their use of "specials" so there are lots of things which are only available through the specialists.

[Rex]

Rex,

"One good reason why not is that it looks so f*****g awful! "

So, just to play devils advocate here, to the untrained (or uninterested) eye, a metric hex head is only superficially different to an imperial. Does this mean the substitution of old fashioned zinc or cadmium plated parts for stainless constitute the same originality faux pas?


Using plated nuts etc is very different from using cheap metric replacements; one is a different thread and size, the other merely a shinier finish, and YOU'D know the difference.....




It's a dialemma for me right now - I have a 1959 T120 which would be quite valuable if it were restored to concours originality, but to be truly original it needs cheap, plated nuts, bolts and spokes. Yet, if I fitted it with stainless it could be devalued despite the obvious advantages. Whaddya do?

Please don't spoil a 59 Bonnie with crappy metric fasteners. Many (including me) would see nothing inherently wrong in using stainless parts, but certainly would in using metric stuff, whatever the finish......

[Searchguru]

"One good reason why not is that it looks so f*****g awful!
It looks like the builder/rider has no idea of engineering, but merely buys his stuff at the local B&Q; not good."

Hi Rex, Henry_norton,

You really have to be realistic. If the machine is not intended as a show-piece but as a useable mode of transport/fun, then why not use whatever is best/easily obtainable.
If a metric nut and bolt can be used where a Whitworth, or whatever was, then use it. Not everyone walks around with a micrometer or vernier guage and is about to pounce on your bike with a thread pitch guage.
Why not try a dab of Loctite or a Nylock nut? I'd rather have all the bits on the bike on my return home than scouring the verges for them.
If, as some would like, you go for purity, then you should have crappy tyres, crappy lights and ride with goggles and a cork helmet/flat cap or none at all.
Heaven forbid you fit electronic ignition to your bike, much better to be cowering at the side of the road in the rain adjusting points.
Originality has it's place but practicality and common sense must prevail. Cheers and a Merry Christmas. Tony B.

[henry_norton]

Ha Ha! No Rex, I wouldn't use any metric or B&Q(!) fittings on my 1959 bike, but I do use stainless which still raises some eyebrows amongst hardcore purists (some of whom don't even own a motorcycle).

My day to day is a 1965 Bonneville which has a 1966 engine (oooh, no matching numbers!!!!), electronic ignition, 2 way damped forks, 12v electrics and I would make no apologies for using any fittings that worked well and lasted.

Anyway, if I can find some of the more standardised Triumph fixings at 'nut and bolt' prices rather than 'classic bike' prices, I'll stick a post on the forum. And a very merry Christmas to you all. Don't forget about your bike in all the merry making. H_N

[Searchguru]

H_N,
Assuming you are in the UK.
Here are two companies I have used on a regular(ish) basis. Both are in the same road in Slough, Berkshire.
Apex Fasteners Ltd, 494 Ipswich Road. 01753 525334
Tunes Engineering Services Ltd, 506-509 Ipswich Road. 01753 536811
I haven't required anything but metric from either, for some time, but both have been in business since dinosaurs roamed the earth, so may well have all sorts languishing on their shelves. You never know.
If they have got what you need at a reasonable price etc. I'm sure there are more potential customers on this forum.