Union to Utility

Union to unsound knot

of sound pressure.
Union. (Plumb.) A coupling or con­nection for pipes.
. Unit magnetic pole. (Elec.) 9ne which will repel an equal and like pole with a force of one dyne at a distance of 1 em. A dyne is the force which, acting upon a mass of 1 gram during 1 second, gives the mass 'a velocity of I em. per sec­ond. .
Unit of capacity. (Elec.) (SEE FARAD.) Unit of E.M.F. (Elec.) (SEE VOLT.)
Unit of illumination. (Elec.) Candle power-The brightness of a lamp. Mean spherical candle power is candle power. averaged over all di­rections from the center of the lamp. Mean horizontal candle power is average candle power in a horizon­tal plane through the luminous center of a lamp.
Unit of magnetic flux. (Elec.) The total number of lines of force set up in a magnetic substance. Treated as a magnetic current flowing in a mag­netic circuit.
Unit of magnetic intensity. (Elec.) Magnetomotive force (M.M.F.) Magnetic pressure which drives lines of force through a magnetic circuit.
Unit of magnetic reluctance. (Elec.) Oersteds. Magnetic resistance. The resistance offered to the magnetic flux by the substance magnetized.
Unit power plant. (Auto.) Consists of the complete motor and transmision and all motor accessories.
Unit stress. (Engin.) The stress on a unit of section area, usually ex­pressed in pounds per square inch.
Universal chuck or concentric chuck. (Mach.) Ajaw chuck whose jaws are so arranged as to permit. simultaneous movement for quick centering of the work.
Universal grinding machine. (Shopwk.)A grinding machine pro­vided with a swivel table, a swivel wheel head, used for external and internal cylindrical grinding, sur­face grinding, face grinding, etc.
Universal joint. (Mach.) A type of coupling which pennits the free rotation of two sha~ whose axes are not in a straight line.
Universal milling machine. (Mach.) A machine tool having both transverse and longitudinal feed. The work is fed against a revolving cutter. It is similar in appearance to the plain milling machine, the principal difference being that the universal machine has a swivel table.
Uni-versal"saw table. (Carp.) A saw table that may be tilted to permit sawing at a bevel.
Unlimited ceiling. (Aero.) Perfect flying weather with cloud level higher than 9000 ft. Unshielded carbon arc welding. A carbon-are-welding process wherein no shielding medium is used.
. Unshielded metal arc welding. A metal-are-welding process wherein the electrode used is a bare or .lightly coated wire or rod.
Unsound knot. (Wood) A knot which is not as hard as the wood it is in.

Ubstable oscillation to Utility
Unstable osciUation. (Aero.) An oscill­ation whose amplitude increases continuously' until an altitude is reached from which there is no tendency to return toward the original altitude, the motion becom­ing a steady divergence.
Upholsterers hammer. A d!)uble pointed hammer having a head 5Y2 in. long, with faces 5/16 to Y2 in. in diameter, making it possible to tack in places wich could not be reached with a hammer of a different type.
Upholsterer's pin or skewer. A needlelike tool about 3~ in. long, having a right formed at one end. It is used.as a temporary basting for covers; It serves as an aid in getting covers in proper position before sewing or tacking.
Upholstery. (Fum.) The act of fitting covering to fumiture~ cushioning, etc. The material used for the same.
Upkeep. (Auto.) The cost of operation and maintenance.
Upper case. (Print.) Capital letters as distinguished from lower-case, small letters.
Upper surface aileron. (Aero.) A split flap forming the rear upper surface of a wing, deflected for lateral con­trol.
Upright. (Arch.) Something standing upright, as a piece of timber in a building. (Furn.) An extension of back legs supporting a chair back.
Upright grain. (Print.) A type of base used when printing unmounted plates, using tacks or catches for fastening.
Upset. (Forg.) To shorten or thicken metal by hammering or by pressure.
Upset butt welding. A resistance butt­ welding process wherein the poten­tial is applied after the parts to be welded have been brought in con­tact and where the heat is derived principally fr9m resistance.
Uranium. (Metal.) A hard malleable metal used to increase strength and toughness of high-speed steels. Also used in small quantities in cast iron. Two principal isotopes are found in natural uranium are U-235 and U-238. Only U-235 is readily fissionable and only I part in 140 of natural uranium is U­235.
Urea. (Plastics) A soluble, white crystalline substance obtained from urine. It is used as a base for urea­formaldehyde resinoids. Also made synthetically.
Urea resin. (Plast.) Aplastic in the ami nos (urea and melamine) family. It is derived from the reaction of urea with formaldehyde of its polymers. Its mar resistance, oil resistane, and surface hardness recommenQs it for such uses as electric mixer housings, buttons, etc. It is also used in the familiar plywood adhesive and lumber laminating field, and for hard-finish coatings. (SEE PLASTICS.)
UseCulload. (Aero.) Tho crew and passengers, oil and fuel, ballast other than emergency, ordinance, and portable equipment. {J.S.F. thread. (Mach.) The United States Form thread has the same shape as the National Coarse, U.S.S. thread but differs in pitch.
Utility. The quality or state of being useful, especially for some practi­cal purpose; also, that which is of practical use.