Mangle and micrometer: what they have in common

1. Step 1. Mangle — has part — Crank. A handle.
2. Step 2. Crank — is part of — Cotton gin. The drum was turned by a handle.
3. Step 3. Cotton gin — uses — Interchangeable parts. Whitney was one of the promoters of interchangeable parts.
4. Step 4. Interchangeable parts — uses — Micrometer. Precise measurement ensures interchangeability.

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