Originally Posted by
habilis
I wonder how the bearing races in the middle portion of a one-piece crank are machined? Even if they lathe-turn it before the crank arms are bent into their final shape, how is the thing even chucked into a lathe? [MENTION=376137]Johnny Mullet[/MENTION], ever go on a factory tour at the Huffy plant?
Marginally off-topic item: I replaced a three-piece, cottered Nervar crank with a cotterless alloy one mainly because the chainring was pressed onto the crank arm and had developed some play in the connection. The alloy cranks with the spider forged onto the crank arm seem better for that reason, as well as the weight reduction. I'm guessing the chainring on a one-piece crank is also pressed on.
The "fixed" bearing race is screwed onto the axle, holding the cainring in place, then the axle is inserted into the frame. Then the other bearing race is screwed on the other side, with a lockring.
The few I have worked on have a separate, loose chainring, held on by the "fixed" bearing race. Both can be removed and replaced.
I assume there are variations over the decades.
Search "ashtabula crankset" for pictures and info.
Back in my racing youth, I had a Huffy type bike I used for bad weather training, and replaced the crank with a BB adapter so I could use a nicer crankset and 9/16 pedals w/ toe clips