1989Pre 

I need to swap some sprockets from a new 5-speed Atom freewheel (French thread) to a new 4-speed Atom (English thread). I know that the sprockets are threaded (they screw on), but does this mean that the transfer is ill-advised?

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fietsbob

Probably ... maybe the cogs off the Freewheel body can me moved .. 'Atom' is long RIP, so You are talking NOS at Best.

Hub threads are like the BB thread So 1 is 34mm , the other Not 34mm .. 1.37" is equivalent to 34.8mm

French thread pitch Is Different too. 1/mm vs 24/inch

1989Pre 

Thanks, fiet. That is what I mean by "sprockets": The individual cogs.

I know that I will need to use an english-thread hub for the 4-speed freewheel, when I get it done. I'm just hoping that I can move the large low gear (28T) off of the french-thread 5-speed and onto the 4-speed without causing a situation where the pedaling of the bicycle would strip the threads on either the cog or the hub.

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Probably ... maybe the cogs off the Freewheel body can me moved .. 'Atom' is long RIP, so You are talking NOS at Best.

Hub threads are like the BB thread So 1 is 34mm , the other Not 34mm .. 1.37" is equivalent to 34.8mm

French thread pitch Is Different too. 1/mm vs 24/inch[/QUOTE]

fietsbob

Consider altering the frame spread (if needed )to accept common 5 speed freewheels , they will be British thread ..
then you can ride the Bike and change the Freewheels as they wear out, cheaply.

I Dont get it? Why not just do the work and find out . is that too 20th century a way of doing Mechanics?

bikeman715

+ 1

JohnDThompson 

Atom made a number of different freewheel bodies with incompatible cogs. Some early Atom freewheels were made in Italy and appear identical to Regina "Corsa" freewheels right down to the nasty 2-prong remover that will destroy the remover slots on the body if not handled carefully. These (like Regina) appear to be based on a body designed for four cogs and support additional cogs by threading the smallest cogs into the cogs above them rather than onto the freewheel body. Others use an oversize remover and have a minimum cog size of 14T, still others allow a 13T to thread directly onto the body and use a nice splined remover.

So, before you get in too deep, make sure what have have will be mutually compatible. Post some pictures if you're not certain.

1989Pre 

Fiet: The bike came with a 4-speed freewheel, so I am not going to change the dimensions of the frame (118mm) for convenience.
I'm not sure what you mean by "do the work". I am doing the research before I do the work, so that I don't make a mis-judgement.

John: Let me see if I have some photos for you. I appreciate the advice.

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fietsbob

A 3 speed hub is made that narrow .

why own a Bike with parts so precious you cannot ride them because the parts were discontinued 50+ years ago?

1989Pre 

That's a little arrogant, presumptuous and mendacious, fiet. My 4-speed freewheel is perfectly useable.
I am not interested in rhetoric: I'm just interested in having my question answered.
What do you say you go ride the bike of your choice and I'll ride one of mine?
3-speed (external) hubs are 115mm.., not 118. 118mm is for 4-speed.

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