Glossary of Compressed Air Terms :: J :: Glossary Index A B C D E F G H I J K L M N O P Q R S T U V W X Y Z Jackleg A pneumatic hand held percussive drill designed as a boring tool. Jack hammer A hand held rock drill worked by compressed air. Jet A stream of vapor, gas or liquid coming out fast from a narrow orifice. Joule A measurement. The international unit of energy. One joule is equal to one WATT - second or 0.737 foot pounds. Joule effect The conversion of mechanical, electrical or magnetic energy into heat. Joule Thompson effect When a perfect gas flows through a throttling with constant inlet and outlet pressures, the temperature of the gas is the same before and after it flows through the throttling. There is a temperature drop, however, during the passage of gas through the throttling device itself. At this point internal energy is transformed into kinetic energy with an accompanying temperature drop. However, for real gases there is a sustained change in temperature, even though the energy content of the gas remains constant. This is called the Joule Thompson effect. Jounce The compression of an air actuator (air spring) below its design height. Journal That part of a shaft or axle that rotates or angularly oscillates in or against a bearing or about which a bearing rotates or angularly oscillates. Journal bearing A sliding type of bearing having either rotating or oscillatory motion and in conjunction with which a journal operates. In a full or sleeve type bearing, the bearing surface is 360 degrees in extent. In a partial bearing, the bearing surface is less than 360 degrees in extent. JTPF Japanese tapered pipe thread (Female). JTPM Japanese tapered pipe thread (Male). Glossary Index A B C D E F G H I J K L M N O P Q R S T U V W X Y Z