Shackle and saw: what they have in common

1. Step 1. Shackle — is part of — Micrometer. A rigid frame.
2. Step 2. Micrometer — is used in — Interchangeable parts. Precise measurement ensures interchangeability.
3. Step 3. Interchangeable parts — is used in — Cotton gin. Whitney was one of the promoters of interchangeable parts.
4. Step 4. Cotton gin — has part — Crank. The drum was turned by a handle.
5. Step 5. Crank — is part of — Sawmill. A crank turns the wheel’s rotation into the stroke of the saw.
6. Step 6. Sawmill — uses — Saw. The cutting tool is a saw.

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