-J-

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