Gas stove and knife: what they have in common

1. Step 1. Gas stove — has part — Valve. Gas taps.
2. Step 2. Valve — is part of — Watt steam engine. A slide valve distributes the steam.
3. Step 3. Watt steam engine — has part — Crank. The stroke of the piston becomes rotation of a shaft (Watt first used a planetary gear).
4. Step 4. Crank — is part of — Meat grinder. A handle.
5. Step 5. Meat grinder — has part — Knife. A cross-shaped blade.

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