from The Century Dictionary and Cyclopedia
- n. In machinery, a nut fitted to a bolt and screwed down hard (jammed) against a principal or holding nut, to keep the latter from working loose through vibrations, jars, or shocks. Also called nut-lock.
Sorry, no etymologies found.
About 6 inches of the plunger is occupied by the packing at the outer end; a solid ring of iron an inch wide, and an inch high, and securely pinned to the plunger, has a leather cup pushed on to it, then a loose ring is slid up against the back of the leather cup and another cup, and another ring, until the space for the packing is filled up; then a nut is screwed up behind these which brings cups and rings tightly together, and a jam-nut with a split-pin going through nut and spindle and opened wide enough to clear the sides of the barrel, and the hydraulic pump is ready for work.