Back in the day, a crank's original forging (hot from the die) was flat, with the four throws opposed 180° apart. The two 3-dimensional 90° throws are obtained by twisting the crank: pulling one throw up and one throw down. The process was called "struck and twisted".
4340 is (IIRC) the frequent material of choice for cranks and other forgings that have large cross-sectional changes.

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