J: Symbol for 1. Gram equivalent weight, 2. the mechanic? l equivalent of heat.
Jack Arch: A spring arch, flat or horizontal on the underside
Jamb: Usually an upright structural member forming the side of an opening in a refractory or furnace wall.
Jamb Brick: A brick modified so one corner is rounded.
Jar Ramming: Packing sand in a mold by raising and dropping on a table the sand, pattern and flask. Jolt squeezers, jarring, machines and jolt
rammers are machines using this principle.
Jersey Fireclay Brick: Highly siliceous clay brick, semisilica brick.
Jet Scrubber: In air pollution control, a high velocity water jet directed into the throat of a venturi section of a cupola to separate out particulates.
Jet Tapping: A method of tapping a melting furnace by firing a small explosive charge instead of using an oxygen lance. The tapper consists of an
explosive charge enclosed in a plastic case surrounded by a hollow bullet-shaped body.
Jib: Projecting part of crane from which lifting chain or gear is suspended.
Jig: Any device so arranged that it will expedite a hand or machine operation.
Jobbing Foundry: A foundry engaged in the manufacture of numerous types of castings not intended for use in its own product. Usually refers to
a foundry making castings for many other companies.
Jolt Ramming: See Jar Ramming.
Jolt-Squeezer Machine: A combination machine that employs a jolt action followed by a squeezing action to compact the sand around the pattern.