The Aggregates & Recycling Information Network

Glossary: J

  • Jar-bar Feeder

    The jar-bar grizzly feeder is a heavy-duty feeder which may form the bottom of the feed hopper of a primary crusher. It consists of a series of bars of elliptical cross-section with the major axes of adjacent bars at right-angles. Material is moved forward by the rotating bars, with a tumbling, rocking motion which makes this type of feeder suitable for applications where fines and clay have to be removed from the feed.

  • Jawstock

    The swing jaw of a jaw crusher.

  • Jet-piercing

    The use of high-velocity jet flames to cut blastholes in hard rock.

  • Jig

    A machine in which the feed is stratified in water by means of a pulsating motion and from which the stratified products are removed separately, the pulsating motion being usually obtained by alternate upward and downward currents of water.

  • Jigging

    A mineral-processing operation in which particles are separated on a density basis by water pulsation.

  • Jim Crow

    A rail bender operated by hand.

  • Job Evaluation

    The techniques of helping to determine a fair day’s pay for a particular job. It is the assessment of the value of the job not the individual and must reflect fairly the skill, experience, responsibility and condition of the job.

  • Jointing Sleeves

    Insulating thimbles placed over the connected ends of detonator leads coupled in large rounds of shots, and over the connections between the detonator leads and the shotfiring cable.

  • Joist

    A beam which supports a floor or ceiling.

  • Joule

    The work performed when the point of application of a force of one newton is displaced through a distance of one metre in the direction of the force.

    Symbol: J (=1Nm)

  • Journal

    The part of a shaft which is supported and held by a bearing.

  • Jumbo

    A drill carriage usually holding several drifters for tunnelling work.