Pitch to Plaster

Pitch of gears to Planetary gear

in one revolution.

Pitch of gears. (Mach.) Refers to the size of gear teeth.

Pitch ratio. (Aero.) Ratio of propeller pitch (geometrical, unless other­wise stated) to diameter PID.

Pitch speed. (Aero.) The product of the me~n geometrical pitch by the number of revolutions of the pro­peller in unit time; i.e., the speed the aircraft would make if there were no slip.

Pitch knot. (Wood) A knot with a . pith hole not more than 1/4 inch diameter.

Pitman. (Mech.) A rod or arm which connects a rotary with a recipro­cating 'part; a connecting rod.

Pit molding. (Fdry.) A method of making large castings in a pit in the foundry floor.

Pitot-static tube. (Aero.) Parallel or coaxial combination of pitot and static tubes. The difference bet­ween impact pressure and static pressure is a function of the velocity of flow past the tube.

Pitot tube. (Aero.) A cylindrical tube with an open end which is pointed upstream, i.e., so that the air meets the instrument head-or is met head-on by the instrument.

Pitted. (Auto.) Pock-marked, Caused by burning or rusting.

Pitting. (Pain; and Lacquer) Spray­ing lacquer in a room where the temperature is less than 65 deg.E, especially with high pressure.

Pivoted casement. (Arch.) A case­ment window pivoted on its up­per and lower edges.

Pivot pin. A point supporting some­ thing which turns.

Plain sawing. (Woodwkg.) Saw cuts taken parallel to squared side of log.

Plain turning. (Mach.) Striaght or cylindrical turning.

Plan. A draft or form drawn on a plane surface as a map; especially a top view or a view of a horizon­tal section; a diagram.

Planchet. (Shopwk.) Blank piece of metal punched out of a sheet be­fore being finished by further work, such as the blank from which coins are made.

Plancier. (Arch.) The underside of the corona in a cornice.

Plane. Level, flat, even. (Woodwk.) (I) A surface in which, if any two points are taken, the straight line which joins them lies wholly in. that surface. (2) A tool for smooth­ing boards or other surfaces of woods. (Mech.) To machine work on a planer. (Woodwk.) By means of a plane, or to machine it on a jointer. .

Planer. (Mach.) A metalworking ma­chine for producing plane sur­faces. The work is fastened to. a table which moves back and forth under the tool. (Print.) A block of hardwood with a smooth sur­face, used with a mallet for lev­eling forms in a chase.

Planetary gear. (Auto.) Consists of .Plane tree to Plaster an internal ring gear, a pinion on a short shaft through which power is applied, and three pinions car­ried on a plate or spider; these three pinions mesh both with the shaft pinion and the ring gear. Plane tree. (Wood) Platanus. Same as buttonwood or sycaniore.

Plane trigonometry. (Math.) A branch of mathematics dealing with the measurment of triangles. Six functions are developed and the relationship existing among these six functions and ther appli­cation to the solution of the right and oblique traingles are of great mathematical importance.

Plan fonn, developed. (Aero.) The plan of an airfoil, as drawn with the chord lines at each section rotated about the airfoil axis into a plane parallel to the plane of projection, and with the airfoil axis rotaed or developed and pro­jected into the plane of projec­tion. Plan form, projected. (Aero.) The ontour as viewed from above.

Planimeter. (Math.) An instrument for measuring the area of any. plane surface, by moving a pointer around its boundary and reading the indications of a scale.

Planing mill. (Woodwk.) A mill or woodworking establil'hment equipped with planning and other machines for surfacing, matching, and fitting boards or planks.

Planish. (Metal.) To smoodl or pol­ish metallic surfaces by hammer­ing or rolling.

Planishing hammer. (Art Met.) A finishing hammer, the style of head being selected to suit the needs of the work. Used for removing ir­regularities and for making bright faceted surfaces.

Plank. (Woodwkg.) A wide piece of sawed timber thicker than a board, usually 1 ~ to 6 in. thick and 6 in. or more wide.
Plank truss. (Arch.) A roof truss or bridge truss built of planking. Plans and specifications (Shopwk.) Drawings and a full set of directions accompanying them.

Pl4nt engineer. Usually a machanical engineer whose p'ractice follows the line of some particular indus­try. His duty consists principally of the construction of plant equip­ment.

Plaque. An oranmented plate or disk, of metal, wood, ivory, procelain, etc.

Plaster. (Bldg.) Made by heating gyp­sum sufficiently to drive off most of the combined water which it contains and grinding finely the dehydrated residue. Mixed pias­ ter is mortar to which a binder is addded and is used for plastering walls and ceilings.