Old Bicycle Parts

jorglueke

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Hi, I am new here driven primarily by my hobby of restoring older bicycles. I am not at present a machinist though I have an interest. I've dabbled in metal working in the past as well but time, and children, and money are all factors as well. Anyway, on to my specific question.

I've come across a cup and cone bottom bracket for a 70mm shell. This is from the 1970's and not normally an issue as the Italian standard was 70mm shells. But the threading on these cups is English. English threaded cups use a 68mm shell so there's one mismatch. The other one is that the spindle is tapered 3 degrees instead of the standard 2 degrees. The best option is probably to find the pieces in better shape than mine, another option is to try and use a modern sealed cartridge which according to some should work but then I can't use the original crank. My question here is how hard is it to machine pieces like this, can they be repaired? The races for the bearings on the moving cup are a bit worn.

I hope this question makes sense.

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They would be darn hard to machine. You could anneal them, machine them, and then re-temper them but the effort would not be worth it.
That's my opinion though. It IS possible.
Mark S.
 
Thank you, that is good to know. Is it the threads that make it difficult, the somewhat complex shape or something else? I will look around here at some beginner projects to get an idea of what is simpler to do.
 
The threads are the easy feature, hardening then grinding the races (if ground in the first place, it is after all a bicycle not an aircraft) will prove more difficult in the hobby shop.

The major question is, once again, how many parts?
 
I wouldn't suggest you alter a vintage crank.
However, depending on the crank design, you might be able to cold grind the ends of a sealed bottom bracket to fit.
I'm near Anoka MN if you want to work on it.
What level of quality (tolerance) do you need?
If this is a rusty enthusiast ride then all you need to do is get it to fit.
If you are working on a classic restoration then we need to up the expectations!

Daryl
MN
 
Last edited:
I wouldn't suggest you alter a vintage crank.
However, depending on the cranks, you might be able to cold grind the ends of a sealed bottom bracket to fit.
I'm near Anoka MN if you want to work on it.
What level of quality (tolerance) do you need?
If this is an rusty enthusiast ride then all you need to do is get it to fit.
If you are working on a classic restoration then we need to up the expectations!

Daryl
MN
way to go Daryl, I see you volunteering a few times since I have been on here. A big thumbs up..
 
The threads are the easy feature, hardening then grinding the races (if ground in the first place, it is after all a bicycle not an aircraft) will prove more difficult in the hobby shop.

The major question is, once again, how many parts?

I don't know if anything is ground. In the pic you can see the wear from the bearings towards the bottom of the cups. I think they just sit in the lip of the cup and then the flared out part of the axel sits right on top and keeps them in place. Grease every 6-12 months and you're good to go until they wear out.
 
I wouldn't suggest you alter a vintage crank.
However, depending on the crank design, you might be able to cold grind the ends of a sealed bottom bracket to fit.
I'm near Anoka MN if you want to work on it.
What level of quality (tolerance) do you need?
If this is a rusty enthusiast ride then all you need to do is get it to fit.
If you are working on a classic restoration then we need to up the expectations!

Daryl
MN

Thanks Daryl. I am of both minds on this, I'd like to ride it restores with the original crank since it is alloy but also it would be fun to try with a cartridge. The latter would cost more as then one needs a new crank as well. The frame isn't rusty except for a few small spots I've treated. I want to get this running because it's a different type of steel and a large bike. If I really liked it I would probably give it a paint job or try to luck out and find a better frame in this size.

As for the grinding the bottom bracket I think that shouldn't be necessary. I have a little difficulty visualizing whether a 68mm or 73mm would be better but because tyhe cartridge's sit flush on the drive side they shouldn't need grinding, the non drive side might just thread in a bit deeper.

But I have some much older projects waiting.
 
Contact me should you have interest in a 30min trip to the Anoka MN area.

Daryl
MN
 
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