Brake lever cotters

[Tony Griffiths]

Which is correct? Design X with the thread concentric with the reduced diameter at the threaded end B1 - B2, or design Y with the thread on the whole diameter centre line A1 - A2?

[bob46320]

Design X is correct (its the way I have made some which copied originals). Design Y causes the thread to foul as the cotter is pressed home

[Tony Griffiths]

Thanks, Bob. Just as I thought; the other makes no sense - and upon looking at bicycle cotters, that's the way they should be made.

[JonE]

so are there some Y in circulation, or were there in the past? I read something about the latter on an old thread but can't remember how old it was.

[Tony Griffiths]

so are there some Y in circulation, or were there in the past? I read something about the latter on an old thread but can't remember how old it was.

I believe that there are - that's why I wondered if the "centre thread" design would work. I suppose, at a pinch, one could imitate the emergency repair my school friend Paul Dougdale carried out on his new, envy-of-the-rest-of-us Claud Butler bicycle - just bash in a filed-down bolt with a lump hammer (only joking - about the Austin - not the Claud Butler).

[Tony Press]

"so are there some Y in circulation, or were there in the past? I read something about the latter on an old thread but can't remember how old it was."

Recent stocks received into our Spares store from the UK were in the incorrect 'Y' style. Needs a big hammer and severe thread bruising to fit

There are a number of cotters of the correct 'X' form, as fitted to early bicycles for many years, available on eBay.

[Bob Culver]

If making yourself use something tough, so less likely to become rivets. (Can leave a projecting thread to pull out). Very old bike cotters had an odd thread size in 1/32 and probably a cycle thread.

[Ruairidh Dunford]

Cotters need to be fettled carefully to fit properly, anyone bashing them in with a big hammer should be wished every success in removing them at a later date.

Those with less neanderthal traits will of course be rewarded with the satisfaction of a press fit (in and out) and a job well done.

[Tony Press]

That is why design X above is needed- check to see if any new cotters purchased recently are of the  correct form

[Tony Griffiths]

Fitting-up the cotters is, as Ruairidh says, important. Why is it necessary to “fit-up”? Because of poor quality pattern parts. Let’s assume that original, Austin-made brake cams, cotters and brake arms would all assemble with ease - and need just a hammer strike on the cotter to bed it in. On a mixture of all-new, or old and new parts, the tolerances might give an Austin-quality fit - though it's more likely that the cotter will a) go straight through or b) hardly go in at all.  For example, upon checking three new (old stock) brake cams, the depth of the "cotter cut-out" in their shaft was found to vary, these being, respectively: 0.311”, 0.323” and 0.331”.  Now, while the difference between the deepest and shallowest is “only” 20 tho, this is sufficient, in the case of b) to require the cotter to be carefully filed. Should the cotter pass right through, or go in so deeply that a pile of washers is needed behind the nut, the only recourse is either to find a better cam -  or modify the cam by silver soldering a piece of thin steel to the bottom face of the cut-out - and then filing it until the cotter fits, not something that you would want do (unless you’re an ace at silver soldering) a few hours before departing for some competition.
Interestingly, the new "concentric" cotter shown below has its thread on the centre line of the full diameter and - having assembled everything on the bench before fitting to the car - works perfectly. Some pictures for your amusement and discussion....