Disk or Disc. A cylinder, whose length is very short in proportion to its diameter; a round plate with a hole in its center.
Double-eye or Knuckle Joint. A joint formed of two forks or jaws with a cube of iron between them, with a bolt or pin through each jaw and the cube at right angles. Will work freely in all positions from a straight line up to 45°.
Double seated poppet valve. A poppet valve having two valves on one stem, with two seats in the same shell.
Double-Seated Poppet Valve.
Drafting water. Another term for “raising“ water by suction, in distinction to “forcing water.”
Drip-pipe. A device used to draw off the water of condensation from systems of piping, steam cylinders, heaters, etc. Drain-cocks are used for similar purposes.
“Dutchman.” A piece “fitted in” to restore a worn part or to hide a defect.
Duct. A passage or conduit.