Black copper to Blending.

Black copper

be regarded, for particular descrip­tive purposes, simply as an entity with input and output connections.
Black copper. Contains about 75 per cent copper. It is obtained by resmelting low-grade copper.
Blackdamp. (Chern.) A term applied to carbon dioxide found in the atmosphere of mines. (SEE CHOKEDAMP ORAFrERD,.\Mp.)
Black gwn. (Wood.) Also known as sour glJm. Tree of medium size. Wood not hard but cross grained and hard to split. Used for wooden kitchenware, excelsior, baskets, and crates.
Blacking. (Fdry.) Ground charcoal, coal or coke dust, or plumbago dusted over the surface of a mold; prevents burning of the sand.
Black lead. (Fdry.) Used for coating patterns and the faces of cast-iron chilling molds.

Black letter. (Print.) A black-faced type usually called "text."
Blacksmith. A smith who forges metal by hand.
Blacksmith drill. (Metalwk.) A drill made with a shank ~ in. in diameter, to fit a certain kind of holder. The shank has a flat for a setscrew.
Black spruce. (Wood) Found in the northern states and Canada; light­weight; reddish in colour; easy to work, though tough in fiber.
Black varnish. Ordinary shellac to which lampblack has been added. Used by pattemmakers.
Black walnut. (Wood) Heavy, hard,. porous wood of a brownish colour; durable. Used for small cabinet­work, gun stocks, and interior decorating.
Blade. The flat, active working part of a tool, instrument, or device, as the blade of a knife, the blade of an oar, the balde of a propeller, etc.
Blade angle. (Aero.) The acute angle between the chord of a section of a propeller, or of a rotary wing system and a plane perpendicular to the axis. of rotation.
Blaae'back. (Aero.) The side of a propeller which corresponds to the upper surface of an airfoil.
Blade face. (Aero.) The surface of a propeller blade which corresponds to the lower surface of an airfoil.
Blade face. (Aero.) The surface of a propeller blade which corresponds to the lower surface of an airfoil. Sometimes called ''thrust face" or "driving face."
Blade-width ratio. (Aero.) The ratio of the developed width of a propeller blade at any point, to the circum-ference of a circle whos~ radius is the distance of that point from the propeller axis.
Blancfixe. (Paint.) Barium sulphate used in the manufacture of paints, made by grinding barytes to a fine powder. When artificially made, the pigment is of finer texture and is known as blanc fixe.
Blank. (Sheet metal) A piece cut from a flat sheet before any form­ing operation has taken place.
Blank and center-punch die. (Sheet Metal) A die which, in one opera­tion, cuts a blank allrl center punches the positions where holes

Blankout commonly used of all the varieties of press tools. The strip of sheet metal is fed under the stripper and is prevented by that member from lifting with the punch upon the upstroke, following the punching out oft~e blank. Where several punches are combined in one hole for blank­ing many pieces simultaneously, they are known as "multiple blank­ing tools."
Blankout. (Tel.) A term used in tuning a receiver when the picture on the cathode ray tube is "erased" or blanked out while adjusting the receiver for picture reception.
Blast. (Fdry.) The volume of air forced into furnaces where combustion is hastened artificially.
Blast romance. (Fdry.) A fumance used for the smelting of iron from it<; ores.

Blast gate. (supercharger) (Aero.). Adevice for controlling the pressure in the nozzle box of a turbosuper charger by discharging into the free atmosphere a portion of the exhaust gases that would otherwise pass through the turbine wheel.
Blasting. The discharge of an explo­sive for the loosening of material; as rock in a quarry.
Blasting powder (SEE Dynamite.)
Blaugas. (Chern.) An oil gas, made by the destructive distillation of pe­troleum, used for lighting, heating, and for cutting steel. Impure pro­pane, C]HS' used for filling Zeppe­lins and foroperzting their engines.
Bleaching. (Wood Fin.) Cleansing or whitening by the use of oxalic acid or some similr substance.
Bleed. (Auto.) To drain off, as, the fluid from a hydraulic brake sys­tem. (Bookbndg.)A book is said to bleed when it has been trimmed so closely as to cut into the print. Il­lustrations bleed when they extend to the very edges of the trimmed sheet.
Bleeder. A small drain cock. Also a by-pass valve.
Bleeding. (Wood Fin.) A term usu­ally applied in connection with the use of mahogany and red dye .stains. Unless the finishing coat is of some quick-setting material such as shel­lac, the undercoat may partially dissolve and "bleed" through the top coat.
Blemish. Any scar or mark which tends to deface a surface.
Blending. (Plast.) Mechanical mix­ing of various ingredients of a molding composition to assure uni­form distribution of all particles; called dry blending or wet blend­ing, depending on conditions. (Wood Fin.) The toning of a finish when applied to a surface to give
-a desured colour effect.