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Glossary of Bridge Terminology



B. and O: Same as "Backing-out Punch."

Babbitt Metal: An alloy of tin with copper and antimony, used for lining bearings and making bushings.

Baby: A bundle of willows or other brush tied together and enclosing small rock, thrown into a stream to protect the bank. More properly termed a "fascine."

Back-filling: Material put back into an excavation around a pier, pedestal, or abutment.

Back-lash: The reaction or tendency to work backward in a pair of gears when subjected to a sudden load. The loose play between the teeth of intermeshing gears.

Back-sight: A level observation, or sighting back, to a turning point or bench mark of known elevation. A transit observation on a previously located point in the rear. A fixed object in the rear which is sighted upon from time to time to check the orientation of the transit.

Back Speed: The second speed gear of a lathe.

Back-stay: A rope or cable extending backward from the head of a mast and fastened to some permanent object. A rear cable in a suspension bridge running from the top of tower to the anchorage.

Back Truck Locomotive: A locomotive having a truck, with a pair of wheels, under its rear end as well as a truck in front of the driving wheels.

Backing: A course of masonry resting on the extrados of an arch; the earth filling behind an abutment; the interior filling of any stone masonry construction.

Backing-out Punch or B. & 0. Punch: A hand tool used by erectors for backing out of the rivet-hole that portion of the rivet remaining after cutting off the head. Also called "B. and O. Punch."

Balance: An instrument used to determine weights.

Balance Beam: The graduated bar of a balance.

Balance Blocks: Small blocks used on counterweights of lift spans to make the final adjustment in counterbalancing the span.

Balance Crane: A crane having two counterpoised arms.

Balanced Load Stress: A stress in a member of a draw span induced by having both arms of the draw symmetrically loaded.

Bale Hook: A large hook suspended from the chain of a crane, used in handling unwieldy boxes and materials.

Balk: A large beam of timber. Sometimes written "baulk."

Ball-and-socket Joint, or Ball Joint: A joint having a spherical surface, or a ball working in a socket.

Ball Bearing: A support designed specially for lessening friction by the use of balls partly contained in sockets, each ball being loose and turning with the object supported.

Ball-bearing Jack: A jack having ball bearings to take up the thrust from the load and reduce the friction of operation.

Ball Check Valve: A check valve formed by a ball resting upon a concave circular seat.

Ball Cock: A stop-cock operated by a hollow sphere or ball of metal attached to the end of a lever which turns the stop cock of a water pipe and regulates the supply of water. Used in concrete work.

Ball Iron: An iron ore containing clay.

Ball Joint: Same as "Ball-and-socket Joint."

Ball Valve: A valve controlled by a float ball. A valve formed by a ball resting upon a concave circular seat, a form of check valve.

Ballast: Gravel, broken stone, slag, or other road material put between the ties of a railroad to prevent them from slipping and to give solidity to the road.

Ballast Hammer: A double-faced, long handled, hand-hammer used in tamping ballast under and around ties.

Ballasted Floor: A bridge floor under a railway track upon which ballast is placed with ties embedded therein.

Balling Furnace: A furnace in which the fagots of metal are placed to be heated, preparatory to working.

Balling Tool: A hand tool used for collecting into a mass the iron in a puddling furnace.

Baltimore Truss: A truss composed of parallel chords and subdivided panels. See Figs. 22c and 22d.

Fig. 22cFig. 22d

Baluster: A small pillar or column, supporting a rail, of various forms, used in balustrades or hand-rails. Also called "spindles."

Band Pulley: A flat or slightly crowned pulley operated by a band.

Band Saw: An endless, narrow band or ribbon of steel with a serrated edge, passing over two large wheels which give it a continuous uniform motion instead of the reciprocating action of a jig-saw, also called a "belt saw" or "endless saw."

Banded Granite: Same as "Gneiss." -- A rock which consists essentially of the same, elements as granite, but having the mica disposed in parallel planes, producing a moderate tendency to cleavage into thick slabs.

Bank Discount: The advanced payment of interest demanded by the bank at the time of making a loan. It is computed as simple interest on the face value of the note for the time given.

Bank Protection: The prevention of erosion of a bank of a stream by the use of riprap, mattresses, or other artificial means.

Bank Sill: A sill placed on the end of an embankment to support the stringers of a wooden trestle.

Bar: Any piece of wood, metal, or solid material long in proportion to its cross-section. Also a barrier. An accumulation of silt, sand, or gravel, or a combination thereof which is deposited in streams and forms an obstruction therein.

Bar Buster: A rivet cutter on the end of a bar.

Bar Cutter: A shearing machine which cuts metallic bars into lengths.

Bar Dolly: A goose-neck or horse-dolly which has an indentation for a rivet head at each end.

Bar Iron: Iron made tip in the shape of bars.

Barb Bolt: A bolt having jagged edges so as to prevent its being withdrawn from the object into which it is driven. Also called a rag bolt.

Barge: A square-ended, flat-bottomed boat having capacity to carry bulky materials such as coal and rock. Used for erecting Spans by flotation.

Barge Spike: A long, slim, square spike with a flat, rounded head.

Bark: The outside covering of trees. To remove the bark from a tree, log, or pile. To scrape.

Barn-siding: Planks that are used to cover the outside of barns, sheds, etc. Generally boards from 13/16 inch to 1 inch thick, and up to 12 inches wide.

Barometer: An instrument for measuring the weight or pressure of the atmosphere.

Barrel of a Capstan: That part of a capstan around which the rope or cable is wound.

Bartizan: A small turret corbelled out at the angle of a wall or tower to form a look-out. Often used in masonry or concrete bridges over the piers and abutments to afford pedestrians a place of refuge or vantage point for sightseers.

Bascule: A moving span that rotates in a vertical plane about an axis that may be either fixed or movable.

Bascule Bridge: A bridge having a span that opens by rotating in a vertical plane.

Bascule-leaf: That portion of a bascule which actually revolves in a vertical plane.

Bascule Span: The moving span of a bascule.bridge.

Base: That portion of any construction which rests on its natural support, such as the bottom of a pier or pedestal. It is generally enlarged as compared with the superimposed construction so as to reduce the intensity of the bearing pressure.

Base Casting: A steel or iron casting upon which the bridge-shoe rests.

Base Line: A line adopted as a fundamental line in a survey from which other lines are run. Used in triangulation work.

Base of Rail: The bottom of any rail laid in final position. It generally determines the elevation from which the heights of the various parts of the structure are measured.

Base Plate: The foundation plate of metal on which a heavy piece of machinery or the end of a bridge rests. This plate is usually set on masonry or concrete.

Basic Open-hearth Furnace: A furnace used in the manufacture of Basic Open-hearth Steel.

Basic Open-hearth Process: That process of producing steel from pig and scrap iron, in which the first step is to remove the phosphorus and some of the sulphur as well as the silicon, manganese, and carbon. This is accomplished by charging the furnace with calcined lime, which unites with the excess phosphorus and holds it in the slag. The rest of the process is similar to the acid open-hearth process. To prevent the slag from attacking the lining, the furnace is covered with dolomitic limestone. Such furnaces are termed basic lined, and the process has become known as the basic open-hearth process because of this lining.

Basic Open-hearth Steel: A metal formed of pig iron, cast iron, and wrought iron or steel scrap, which is converted into steel in a furnace having a lining of dolomitic limestone in order to resist the action of the slag. This slag contains much of the phosphorus in combination with calcined lime with which the furnace is charged. In this way the phosphorus content is reduced materially.

Basic Pig: Pig iron used in making basic open-hearth steel in which the silicon content is limited to one per cent and the sulphur to one-half of one per cent.

Basil: The angle at the cutting edge of a tool or instrument.

Basing: A finished projection around the bottom of a column located just above the ground level; similar to the baseboard of a room.

Basket Crib: A form for pier foundations in the shape of a basket. This type was used on the Chelsea Bridge at Boston.

Bastard File: A file having an intermediate surface between that of a smooth and a rough file.

Bastard Granite: See "Banded Granite"

Bat: A broken brick.

Bat Bolt: A bolt barbed or jagged at the butt, or tang, to give it a firmer hold.

Bateau Bridge: A floating bridge supported by boats or barges. A pontoon bridge.

Bath-tray: A tray, generally of zinc, used for washing blue prints in a water bath.

Batten: A strip or scantling of wood. A bar nailed across a group of parallel boards to hold them together. To tie down or fasten securely.

Batten-door: A door made of sheathing, secured by strips of boards, placed cross ways, and attached with clinched nails.

Batten Plate: A stayed plate at the ends of a compression member. Sometimes termed tie plate or stay plate.

Batter: To strike with repeated blows. An incline from the vertical; said of a wall having a face receding as it rises. To incline a face or line in masonry or any other construction.

Batter Brace: The inclined end post of a truss, sometimes called the "Batter Post."

Batter Pile or Battered Pile: A pile driven at an inclination to the vertical.

Batter Post: Same as "Batter Brace."

Battered Pier: A pier having its sides slightly inclined to the vertical, giving a larger section at the. base than at the top.

Battered Pile: Same as "Batter Pile."

Battering Ram: A beam of timber, generally having a metal head, used to drive home bridge pins. Sometimes it is made entirely of metal where a great many large pins are to be driven. A railroad rail is sometimes employed as a battering ram.

Battery: A number of voltaic cells arranged together to give a powerful electric current.

Baulk: Same as "Balk."

Bay: The portion of a trestle between two columns. The English term for a panel of a truss.

Bead Joint: Mortar in a masonry joint forming a bead.

Beam: A member the principal function of which is to carry a transverse load.

Beam Compass: A bar having two slides mounted thereon, one holding a steel point or centre, and the other the marking-pencil or pen -- used for striking large circles.

Beam Hanger: A rod or square bar supporting a floor-beam from a chord pin.

Beam Hanger Nuts: The nuts on the ends of beam hangers, serving to press the floor-beam against the feet of the posts or against the chord-heads.

Beam-hanger Plate: The plate beneath the ends of a floor beam for the beam-hanger nuts to press against.

Beam Span: A span built with beams.

Beam-trussing Posts: The short, perpendicular posts used in trussing beams.

Beam Trussing Rods: Rods which are run beneath the tension side of a beam to form, in connection with one or more struts, a system of trussing to strengthen the said beam.

Bearing: The angular position of a line referred to a meridian. The support for a shaft, axle, or trunnion. The shoes for 'a span. The resistance to crushing as offered by a member. The pressure transferred from one member to another. The capacity of a pile to carry load. The support for a beam, pin, bolt, or rivet.

Bearing Pile: Any pile carrying a vertical load.

Bearing Plate: A plate which receives the bearing from a pin or a plate that bears on another plate.

Bearing Point: The point of support for a load or a place where concentrated pressure is applied.

Bearing Pressure: The pressure on a bearing.

Bearing Stress: The stress developed in a bearing by the superimposed load.

Beater: A bridgeman's term for a maul.

Becket: A short piece of rope with a knot at one end and a loop, or eye, at the other. A handle made of a rope sling. An iron U-strap fixed to a pulley block, so as to provide a loop for attaching a rope.

Becket Block: A hoisting block having a becket to which a rope may be attached.

Bed: A surface or-body of rock, earth, or shale which serves as a foundation. The foundation piece on which a machine rests. A layer of cement or mortar in which the stone is embedded. To place stone or brick in mortar. To embed. To place a thing on its bearing.

Bed Frame: The frame on which the bed of an engine rests.

Bed Joint: A horizontal joint or one perpendicular to the line of pressure on the masonry.

Bed Plate: A plate set in the top of the masonry to carry the load from the span.

Bed-rock: The solid rock lying under loose detrital masses, such as sand or gravel.

Bed Stone: One of the stones in a bottom course of masonry.

Beetle: A heavy wooden mallet used to drive wedges, also to consolidate earth.

Belay: To make fast around a belaying-pin, cleat, or cavel.

Belaying-pin: A wooden or iron pin to which a rope is belayed or tied.

Belgian Tank Locomotive: A locomotive having a tank on each side of the boiler.

Bell: The large end of a pipe or tube turned out in the shape of a bell.

Bell and Hopper: A charging device on top of a blast furnace.

Bell Crank: A bent or rectangular crank lever by which the direction of motion is changed ninety degrees, and by which the velocity ratio and range may be altered at pleasure through making the arms of different lengths.

Bellows: An apparatus or box with flexible leather sides so arranged by means of a valve that it may be opened and closed in succession, thereby producing a current of air.

Belt: A course of stones or bricks projecting from a structure, generally lying in a horizontal plane. Sometimes called a "stone-ring." Also a flexible strip of leather, rubber, or any other material which passes around the periphery of wheels, drums, etc. for transmitting motion from one to the other.

Belt Saw: Same as "Band Saw."

Belted: Driven by a belt.

Belting: The material from which belts are made. Also a general term for a number of belts taken collectively.

Bench: A table upon which mechanics do their work; a ledge made on the edge of an earth cutting in order to strengthen it.

Bench Dog: A hook-shaped iron fastened to a bench for holding in place materials, such as wood.

Bench-mark: A mark cut in a rock or located on some permanent object to record the elevation at that place in a line of levels.

Bench-table: A low stone scat carried around a wall.

Bench Vise: A vise constructed so that it may be attached to a bench.

Bend: A band or clamp of metal used to strengthen a box or frame. The action of bending, or the state of being curved.

Bending Moment: The moment which produces or tends to produce bending in a beam or other member of a structure. It is measured by the algebraic sum of the products of all the forces by their respective lever arms.

Bending Slab: A plate of metal with holes punched in it for holding pins around which thin plates or bars may be bent to required shape.

Bending Stress: The stress produced in a member by a bending moment.

Bending Test: A test made by bending bars to determine their comparative brittleness. A test made on beams to determine their moduli of rupture.

Bends: A pneumatic caisson disease, due to the abnormal air pressure. It is a species of temporary paralysis.

Bent: A condition of being curved or kinked. A supporting frame consisting of posts or piles with bracing, caps, and sills.

Bent Club Dolly: A club dolly having a bend in the hammer or anvil.

Bent Dolly: A dolly with a bent offset at the centre and only one end having the cup-shaped indentation for the rivet heads.

Bent-eye: An eye on the end of a bar, the plane of which makes an angle with the direction of the bar. Formerly used in bridges, but now abandoned as unscientific.

Bent-linked Chain: A coil chain in which the links are bit or bent.

Bent Loop: A loop eye-bar in which the loop is bent in respect to the direction of the length of the bar.

Berm or Berme: The portion of the supporting soil of an embankment lying between the toe thereof and the side-ditch.

Berme Stakes: Stakes showing the side lines of a berme.

Bessemer Furnace: A furnace mounted on trunnions so as to be tilted in either direction and having air-blast connections through the trunnions, used for converting pig iron into Bessemer steel by a process of decarburization.

Bessemer Pig: Pig iron used in making Bessemer steel or acid open-hearth steel, in which the silicon content ranges from one per cent to two per cent; phosphorus not over one-tenth of one per cent; and sulphur not over one-half of one per cent.

Bessemer Process: A process for making steel by the decarburization of crude pig iron by means of a finely divided air current blown through the metal when in a molten state. Named from its inventor Sir Henry Bessemer.

Bessemer Steel: Steel made by the "Bessemer Process."

Bethlehem Beam: A special rolled beam having a thin web and wide flanges made in the Gray mill of four rolls. Manufactured by the Bethlehem Steel Company.

Bethlehem Column: A wide "H" column rolled in a four-roll mill by the Bethlehem Steel Company, similar to that of the "Bethlehem Beam."

Beton: A mixture of lime, sand, and gravel forming a kind of concrete. Sometimes used as a synonym for concrete.

Beton-Coignet: A mixture of Portland cement, siliceous hydraulic lime, and clean sand mixed together with fresh water." Named after its French inventor, a Monsier Coignet.

Bettle: a heavy wooden rammer. A workmen's corruption of "Beetle."

Bevel: The slope on the end of a piece; an instrument for drawing angles-used by mechanics. To slope or sharpen an edge.

Bevel Gears: Gears having teeth arranged around the convex surface of a conical wheel in the direction of a radial plane passing through the axis of the cone.

Beveled-edge: An edge that is made thin by bevelling.

Beveled-gear Jack: A jack operated by power applied through bevel gears.

Beveled Joint: An angle joint in which the contact surfaces make equal angles, other than a right angle, with the axes of the parts joined.

Beveled Tie: A railroad tie in which the top and the bottom faces are closer together at one end than at the other.

Beveled Washer: A washer having one side beveled to compensate for the angle between the bolt and the timber through which the bolt passes.

Beveled Wheel: A wheel having a sloping face.

Bicalcic Silicate: A union of calcium and silica (2CaO.SiO2).

Bid: To make a price on anything. A proposition, either verbal or written, for doing work.

Bight: A loop of a rope in distinction from the ends; any bent part or turn of a rope between the ends.

Bill of Material: A list of the various portions of material for a construction, either proposed or completed, giving dimensions and weights or other quantitative measurements.

Billet: A small bloom; a short, chunky bar of iron or steel.

Bin: A place for storing materials, such as cement, sand, or broken stone.

Binder: A substance that will hold, or will bind together, different materials or the numerous parts of the same material, such as bitumen. This term is generally used in reference to pavements.

Binder Course: That portion of a pavement connecting the wearing surface to the base.

Binding Joists: Joists used as girders to sustain common joists.

Binocular: A double telescope for the use of both eyes.

Bird's-mouth Joint: A joint in timber where an inclined member is dapped over a horizontal member.

Bit: A tool for boring into wood or metal.

Bite of a Line: The enclosed space between the parts of a line which passes through a pulley-block or a hook.

Bitt: A strong post of wood or iron to which cables are made fast.

Bitumen: Any native mixture of hydro-carbons oxygenated, as naphtha, and especially asphalt.

Bituminous Cement: A cement or mastic in which bitumen, usually in the form of asphalt, is the chief ingredient.

Bituminous Concrete: A concrete composed of bitumen, sand, and broken stone.

Black Lead: Same as "Graphite." -- A form of carbon. Used for lead pencils, lubrication of machinery, the rubbing surfaces of wood, and as a conductor in electrical construction. Also employed as a pigment for paints used in structural steel work

Black Lead: Same as "Graphite."

Black Lead Graphite: See "Black Lead."

Blacklead: A name sometimes used for "Graphite." See "Black Lead."

Blacksmith's Forge: A small forge used by a blacksmith.

Blank Bolt: A bolt having a fixed head, but no threads nor nuts.

Blast Furnace: A furnace used in smelting iron ore.

Blast Pipe: The exhaust pipe of a steam engine.

Bled Ingot: Ingots from the center of which molten steel has escaped, leaving a cavity.

Blind Arch: An arch in which the opening is walled up.

Blind Axle: An axle that does not communicate power; also called a dead axle.

Blind Header: In masonry, a header stone or brick that is hidden from view.

Blister: To raise filmy vesicles on a surface by heat. A small raised portion of a metal surface with a void beneath.

Blister Steel: Steel made from wrought iron by heating it while in contact with some form of carbon.

Block: Any obstruction or cause of obstruction; an obstacle. Any solid mass of matter usually with one or more plane faces; such as a block of wood, metal, stone, etc. A combination of a frame with one or more grooved pulleys, or sheaves, held therein; used in connection with ropes to multiply force. Also called "pulleyblock." To obstruct. To support with blocks, as to block up.

Block and Block: The condition of the two blocks in a tackle when drawn up close together. Also called "Two Blocks" and "Chock-a-block."

Block and Falls: A set of pulley blocks with hemp ropes or steel cables roven through them; used for hoisting purposes or for exerting a strong pull. Also called "Block and Tackle."

Block and Tackle: Same as "Block and Falls."

Block Brake: A brake used in retarding a moving part by pressure from a stationary block.

Blocking: The set of blocks which is placed under anything to raise and support it.

Blocking Hammer: A hand hammer which has a head that is diamond shaped.

Bloom: A roughly prepared mass of iron or steel nearly square in section and comparatively short in proportion to its thickness.

Bloomated: Made into blooms.

Blooming Rolls: Rolls in which puddle balls of iron or steel are squeezed into blooms.

Blow: That portion of the time occupied by a certain stage of a metallurgical process in which the blast is used. To explode. In caisson work the term " blow " refers to the letting of air out of the working chamber so that the caisson may drop.

Blow Gun: A barrel or pipe through which material is blown.

Blow-hole: A defect in iron or steel caused by the escape of gas or air while solidifying.

Blow-out: The mechanism for blowing material through a pipe or tube. The bursting of forms, or shells, holding material, such as concrete. The sudden escape of air from a caisson.

Blow Pipe: A pipe through which material is forced by air from a caisson. A small tube through which air is forced so as to produce a high temperature.

Blowing of Mortar: Mortar placed by compressed air forcing it through a pipe or nozzle.

Blue-print: A copy made on blue-print paper from a tracing.

Blue Print Paper: A paper coated on one side with a preparation of potassium ferrocyanide which is sensitive to light. It is used for copying maps, plans, etc.

Blue Printing: A method of photo-printing by using paper sensitized with ferroprussiate of potash.

Blue-short Iron: Wrought iron that has been injured and rendered brittle by being worked at a blue heat.

Blue-shortness: A condition of brittleness in wrought iron caused by its having been worked at a blue heat.

Blunt File: A file terminating in a blunt end.

Board-measure: The standard measure for timber, the unit being a piece one foot square and one inch thick. Timber is sold at so much per thousand feet board measure usually written "per M.B.M."

Boasted Dressing: A finish in stonework wrought with a chisel or narrow tool.

Boasting: A mason's process of dressing the surface of a stone with a broad chisel and mallet.

Boat Bridge: Same as "Bateau Bridge" (A floating bridge supported by boats or barges. A pontoon bridge.) or "Pontoon Bridge (A platform or roadway supported on pontoons or barges. A floating bridge)

Boat Hook: A brass or iron hook and a spike fixed to a staff or pole, used for pushing or pulling a boat or barge. At times called a "Gaff-setter," "Setting Pole," "Pole Hook," and a "Hitcher."

Boat Ratchet, or Steamboat Ratchet: An apparatus for pulling, consisting of a sleeve having internal, opposing threads at the ends and a ratchet and handle for turning the same. Suitably threaded rods with links and hooks at the outer ends screwed into the sleeve. The turning of the sleeve screws up on the rods causing them to approach each other.

Boat Spike: A square, chisel-pointed spike with a rounded head, ordinarily from eight to ten inches long, used to fasten heavy planks in wooden floors, railroad crossings, etc.

Bog Iron: An iron extracted from ore occurring in marshy ground.

Bogie: A small truck, or carriage, running crosswise of a saw-mill carriage to shift the log at right angles to its length when on the main carriage.

Bogie Truck: A railway truck mounted on two or more pairs of wheels and attached to a car or locomotive engine by means of a vertical king pin about which it turns so as to facilitate the rounding of curves in the track.

Boil: To bubble up or be in a state of ebullition through the action of heat. A whirl or vortex in a stream.

Boiler: A vessel or receptacle in which any liquid is boiled.

Boiler Plate: Iron or steel rolled into flat plates from one-quarter to one-half inch thick, used in making tanks, boilers, vessels, etc. Sometimes called "boiler iron."

Boiler Steel: A medium steel rolled into plates from one-fourth to one-half inch in thickness and used for making boilers.

Boiling Test: A test for determining the constancy of the volume of cement. Pats of cement mortar are made, protected against drying for twenty-four hours, then put in hot water or steam for five hours, after which they are removed and observed for signs of cracking and disintegration. If no such signs appear, the cement has proved satisfactory in respect to soundness.

Boiling Test of Cement: Same as "Boiling Test"

Bollman Truss: A trussed beam, each panel-load being carried directly to the ends of the upper chord by two inclined tension members, there being no stress in the lower chord. Properly speaking, it is not a truss, but a multiple suspension system. See Fig. 22o.

Fig. 22o

Bolster: A perforated wooden block upon which sheet metal is placed to be punched. A sleeve-bearing through which a spindle passes. A bar placed across the middle of a car truck to support the body. In stone sawing, one of the loose wooden blocks against which the ends of the pole of the saw rests. One of the transverse pieces of an arch centering. A timber or thick iron plate placed between the end of a bridge and its seat on the abutment.

Bolt: A cylindrical jet, as that of water. A metallic pin or rod having a head at one end and a thread on the other for screwing up a nut. Used for holding members or parts of members together.

Bolt Eye: The eye in an "Eye Bolt."

Bolt Head: The enlarged end of a bolt having a square or hexagonal shape.

Bonanza Tile: A reinforced composition cement tile used in roofing.

Bond: Anything that binds, fastens, or holds together pieces of material, as the connection of one stone to another. A certificate of ownership of a specified portion of a capital debt due by a government, a city, a railroad, or other corporation, to individual holders, and usually bearing a fixed rate of interest. Also an electrical connection, such as a bar of copper wire soldered to two track rails near their junction. Also the manner of laying bricks or masonry stones. A guarantee.

Bond Resistance: The resistance offered to the slipping of a reinforcing bar when imbedded in concrete.

Bond Stress: The longitudinal stress set up between the surface of a reinforcing bar and the surrounding concrete.

Boning: A method used by carpenters and masons to determine whether a surface is in or out of wind. It consists in placing two similar straight edges on the surface, parallel to each other, and sighting over their upper edges to see if they coincide. If they do not, the surface is in wind.

Bonnet: A cap over the end of a pipe. A cast-iron plate bolted down as a covering over an opening.

Boom: A long beam or spar projecting from near the foot of a derrick, and sustaining the load that is raised from its outer end. In England the term is used as a synonym for a chord of a truss.

Boom Brace: A tackle extending from the end of the boom to the top of the mast in a derrick. The trussing placed below or at the sides of the boom to strengthen it.

Boom Guy: A line, cable, or adjustable rod fastened to the middle of a derrick boom and extending to the bull-wheel to which it is attached so as to act as a brace.

Boom Iron: A circular iron ring on the end of a mast of a derrick.

Boom-out: The position of the boom at its greatest reach.

Boom-seat: The place in a derrick where the boom and the mast meet and rest on the sill.

Boom Tackle: The tackle used for manipulating the boom of a derrick.

Bore: To make a hole in any material by cutting away a part of it. To drill. The calibre, or internal diameter, of a hole, tube, or pipe.

Boring: Any hole that has been bored, such as a boring for a pier foundation.

Boring Bar: A machine tool consisting of a special bar with cutters attached, used in a lathe or boring machine.

Boring Casing: A wrought-iron pipe from 2 1/2 inches to 3 inches or more in diameter placed outside of the churn pipe, used in drilling test holes for pier foundations.

Boring Machine: A machine used for boring holes.

Boring Mill: A large machine tool having a horizontal revolving table to which the object to be trimmed is fastened, and in which the cutting tool, except for feed adjustment, remains fixed in position while the object revolves. Used for turning large castings and boring large holes.

Borrow-pit: An excavation made by the removal of material, specially for use in filling or in building an embankment.

Bosh: A rough sketch, an outline, or a figure. A trough in which bloomery tools are cooled.

Boss: The enlarged part of a shaft on which a wheel is keyed. A wooden vessel used by plasterers for holding mortar. A foreman or sub-foreman. One who directs work.

Boston Rod: A leveling rod in which the target is fixed to the sliding part of the rod. This is raised or lowered by the rodman until the target is in the line of sight, then clamped and read by the rodman by means of a scale on its face.

Bottom Chord: The lower member of a truss, usually resisting tension.

Bottom Lateral Bracing: Lateral bracing in the plane of the bottom chords of a truss.

Bottom Laterals or Lower Laterals: Laterals in the plane of the bottom chords.

Bow: An arch of masonry, as in the gateway of a bridge. A flexible strip which can be bent to any desired curve, or an arcograph used in drafting.

Bowstring Girder: A girder consisting of a curved rib or beam, having a horizontal tension member arranged as a chord and connected to the rib by vertical tie rods.

Bowstring Truss: A truss in which the lower chord is horizontal and the upper chord joints lie in the arc of a parabola, or similar curve. See Fig. 22s.

Fig. 22s

Box: A cap that covers the top of a pump. A one-piece bearing, or support, for a shaft or journal. A casing about a valve. To form into a box or the shape of a box.

Box Beam: A hollow beam, generally rectangular in section, having its sides made of plates united by angle-irons.

Box Column: A column made in the shape of a box, having sides of steel plates united by angles.

Box Culvert: A square or rectangular shaped culvert.

Box-drain: Same as "Box Culvert."

Box Girder: A type of girder having two webs giving a section resembling a box made tip of plates and angles riveted together and forming flanges and webs.

Box Strut: Any strut built of structural shapes having a box-like cross-section.

Brace: Generally a strut supporting or fixing in position another member. Some times the term is applied to a tie used for such a purpose. The permanent part of a small tool used for boring.

Braced: Strengthened or well interlaced and linked together by bracing.

Braced Arch: An open-work truss in the form of an arch.

Bracer: A brace.

Bracing: A system of braces, as in lateral systems.

Bracing Frame: A frame of steel or timber built in a manner to withstand distortion.

Bracket: A knee, or knee brace, connecting a post or batter brace to an overhead strut.

Bracket Crab: A hoisting apparatus fastened to a wall.

Brad Awl: A short non-tapering awl, with the cutting edge on the end, for making holes in wood to receive brads, screws, etc.

Bragger: Same as "Corbel." -- A small shelf cantilevered out from a beam, wall, or column in order to support a beam or a superincumbent load.

Brake: A mechanical device for arresting or retarding the motion of a machine or vehicle by means of friction. To retard or stop motion by the application of a brake.

Brake Horsepower: Same as "Actual Horsepower." -- The actual horsepower of an engine as measured at the flywheel by a friction-brake or a dynamometer.

Brake Wheel: A heavy wheel furnished with cams to control the action of a trip hammer; the wheel of a band-brake.

Braked-train: A train in motion with the brakes set and the steam shut off.

Brass: An important alloy consisting of copper and zinc. The detachable part of a bearing in immediate contact with the shaft or journal.

Braze: To cover with brass. To solder with a special hard solder.

Breach: A break, as a breach of contract, or a breach in an embankment.

Break in Grade: That point where the grade changes. The change itself.

Break Joint: To overlap pieces so that the joints will not occur near together, avoiding thereby excessive weakening of the member.

Breaking Joint: A joint formed by the ends of several component pieces in one line, no two lines being cut at the same place.

Breaking Load: A load which when placed upon a structure or test piece would just be great enough to break it.

Breaking Stress: The stress developed in a member at the point of rupture.

Breakwater: Any structure, such as a mole, mound, wall, or sunken hulk, to break the force of waves and protect harbors.

Breast Plate: A plate on a tool for the operator to press against, such as the breast plate on a hand drill.

Breast-summer: A beam of wood, iron, or stone supporting a wall over a door or other opening; a kind of lintel.

Breast Wall: Same as "Retaining Wall." -- A wall built to sustain a lateral pressure, such as an earth thrust

Brestummer: Same as "Breast-summer."

Brestsummer: Same as "Breast-summer."

Brick: A kind of artificial stone made of moistened and finely kneaded clay molded into rectangular blocks and hardened by burning in a kiln.

Brick Masonry: Masonry composed of brick, usually termed brickwork.

Brick Pier: Any pier made of bricks.

Bricklayer's Hammer: A hammer having a bent peen, used in brick work.

Bridge: A structure that spans a body of water, a valley, or a road and affords passage for pedestrians, or vehicles of all kinds, or any combination thereof.

Bridge Guard: A timber or other construction, usually in the form of a large post sunk deep into the ground near the end of a bridge so as to prevent its being struck by either derailed cars or badly shifted loading.

Bridge-seat: That part of the top of a bridge pier or abutment that receives directly the pedestals or shoes of the superstructure.

Bridge Stone: A flat stone bridging a gutter or other small opening.

Bridge Tape: A strong flat wire divided by clips into feet, with the two end feet divided decimally.

Bridge Truss: Any truss used in a bridge span.

Bridging: A piece of wood placed between and attached to two beams, or other pieces, in order to prevent them from approaching each other. It also means the spanning of any opening.

Bridging Joists: Common joists.

Bridging Stone: Same as "Bridge Stone."

Briggs' Logarithm or Common Logarithm: A system of logarithms in which the base is ten.

Briquette: A standard shaped form or block made of cement or of mixed cement and sand; used for testing the tensile strength of the neat cement or of the mortar.

Briquette Clips: The clips or jaws on a cement testing-machine which hold the briquette while being stressed.

Briquette Mould: A standard form used for making briquettes out of mortar.

Bristol-board: A high quality of calendered cardboard used for fine drawings, printing, etc.

Brittle-zone: In nickel steel testing, the stage between certain inferior and superior limits for percentage of nickel in the alloy where the metal is brittle, and both below and above which it is not.

Broach: A boring bit or tapering tool for enlarging and smoothing holes. A reamer. Also a narrow-pointed chisel for dressing stone.

Broached Dressing: A finish in stonework wrought with a "punch" after the surface has been droved.

Broad Axe: An axe with a broad blade on one side and a hammer head on the other.

Brohard Expansion Bolt: A bolt with a screw attachment and a screwed collar over it. This bolt is used in concrete after hardening. A hole is driven, the collar inserted, and then the bolt is screwed in.

Broken Ashlar: Cut-stone masonry formed of ashlar blocks but laid so that the horizontal joints are discontinuous.

Broken-ashlar Masonry: An ashlar masonry in which the bed joints are discontinuous at intervals, due to the use of smaller blocks of stone in making up the course.

Broken Axed Dressing: A stonework dressing made with an axe to resemble "Crandalled Dressing."

Broken Coursed Rubble, or Broken Range Rubble: Rubble masonry laid in partial courses and having abrupt changes in thickness thereof.

Broken Line: Any line composed of two or more straight lines.

Broken-range Masonry: A range type of masonry in which the courses are not continuous throughout, due to their being made up at intervals of smaller blocks of stone.

Broken Ranged Rubble: Same as "Broken Coursed Rubble."

Broken Stone: A term applied to rock which is crushed or broken into small pieces and used for concrete, road pavement, ballast for tracks, etc.

Broken Stone Concrete: A concrete composed of cement, sand, broken stone, and water.

Broken Top Chord: A top chord in which each successive segment deviates or deflects from the line of its contiguous segment, at the panel point.

Bronze: A reddish-brown alloy of copper and tin, sometimes containing small portions of other metals. Used in bridgework for journal or pivot bearings and for nameplates.

Bronze Steel: An alloy of copper, tin, and iron used as gun metal.

Brooming: The breaking up under hammering of either the head or the point of a timber pile and reducing it to a fibrous mass.

Brushes: The copper wires, plates, or carbon connections which make contact with the commutator on a dynamo or motor and serve to take off the electric current.

Bubble: The vesicle of air or gas in the glass spirit-tube of a mechanic's or surveyor's level. A blister on a steel surface.

Buck: To resist. To afford resistance. To press against a rivet-head with a dolly during driving.

Buck Brace: Same as "Cross Frame." -- A transverse bracing frame between stringers.

Bucker-up: One who holds a dolly-bar on the head of a rivet while it is being driven.

Bucket: A vessel for drawing up water or materials, as from a well. One of the scoops of a dredging machine. In general terms, any contrivance used for carrying materials in hoisting.

Bucket Dredge: A dredge which hoists out the material by the use of buckets usually attached to an endless chain.

Bucket Hole: The hole or shaft in which a bucket travels.

Bucket Pump: A pump for raising liquids by means of buckets attached to a belt or chain and passing over an overhead shaft or a pulley or sprocket wheel.

Bucking Bar: The bar on a ring dolly which bears against a rivet, so as to hold the head during driving.

Buckle: To bend in a lateral direction by a longitudinal pressure.

Buckle Plate Floor: In bridgework a floor system that is composed of buckle plates for supporting pavement.

Buckle-plate Press: A machine for pressing sheet steel into buckle-plates.

Buckle Plates: Flat, steel plates which are dished at regular intervals. Used for floor plates.

Buckling Stress: A compressive stress so great that the elastic limit of the piece is exceeded, and, in consequence, a buckling or bulging of the material occurs.

Buffer: Any apparatus for deadening the concussion between a moving body and another body against which it strikes.

Buggy: A small wagon used for transporting material such as rock. The carriage on which a traveling crane rests.

Build: The manner of construction. The form of anything. To frame, construct, or erect. The height of a cut masonry stone or its rise, used in contradistinction to its bed, as a "build joint" or a joint in a vertical plane.

Builders Hoist: A hoisting apparatus in which the boiler, engine, gearing, and drum are mounted on the same bed.

Built Beam: A beam made up of structural shapes, such as plates and angles, riveted together.

Built Channel: A shape in the form of a channel fabricated from a plate and two angle irons.

Built Girder: A girder made up of structural plates and angles.

Built Pile: A pile made up of several parts.

Bulb Angle: An angle-iron section in which one leg has a bulb on one end.

Bulk: The body of a substance. A painter's term applied to pigment to signify the total volume thereof plus the voids.

Bulkhead: A partition built in a tunnel or conduit to prevent the passage of air, water, or mud, or in a form for concrete.

Bull-dog: Calcined tap cinder from puddling furnaces.

Bull Gang: A crew of unskilled laborers for moving steel from the store yards to the bridge site.

Bull Press: Same as "Gag Press." -- A press consisting of two fixed horns and a ram, used for straightening structural shapes.

Bull Riveter: A form of stationary, yoke riveter set in a vertical position and having a large air cylinder at the end of one of the arms. The piston moves with a short stroke in a horizontal direction and the former on the end of the piston rod upsets the shank and forms the head in one movement of the piston.

Bull Wheel: A large, horizontal wheel connected to the foot of a derrick mast for the purpose of turning the derrick with ropes leading to the hoisting engine.

Bull-Wheel Derrick: A derrick with a bull wheel attached to the bottom of the mast in order to swing the derrick by ropes running to the hoisting engine.

Bull Wheel Pile Driver: A pile driver having a bull wheel for winding up the leadline and raising the hammer. Pins are set in the periphery of the wheel convenient for the men to grasp and pull upon, thus rotating it.

Bulldozer: A machine in which angles are bent in small circular arcs by pressure between two supports.

Bunker: A bin used for storing purposes, such as the storing of coal or any other loose material.

Buoy: A float fixed at a certain place to show the position of any object beneath the water's surface.

Buoyancy: The upward pressure exerted upon a body by the fluid in which it is immersed. It is equal in amount to the weight of the water displaced.

Buoyant Effort: Same as "Buoyancy,"

Buried Pier: A small secondary pier built a short distance from the main shore pier and carrying the end of an approach span. It takes the place of an abutment and is more economical, as it has no wing-walls and does not have to resist the lateral pressure of the earth, because the embankment spills around it on all sides.

Burlap: A coarse, heavy cloth or mat made from jute, flax, hemp, or manila fibres.

Burning Steel: A mechanical separation of the grains due to extreme overheating of steel.

Burnish: To polish by rubbing; applied chiefly to metals.

Burnt Steel: Steel that has been overheated in the making or remelting. It is coarse-grained and very brittle when either hot or cold.

Burr: A partially vitrified brick; a clinker. A protuberance or raised portion of an object. A nut with a screw-thread. The rough projecting edge of a drilled hole in steelwork.

Burr Truss: A timber truss with counter-struts inserted throughout the entire length giving very great rigidity.

Bush: A perforated box or tube of metal fitted into certain parts of machinery. To dress stone, or the manner of dressing it.

Bush Hammer: A mason's finishing hammer having regular rows of points or projections on its faces.

Bush Hammered Dressing: A finish in stonework wrought with a bush hammer.

Bushel: A unit of dry measure containing 2,150.42 cubic inches.

Bushing: Same as "Bush."

Bust Hammer: A hammer, used in riveting work, having a rivet blister on one end of the head and a hammer on the other end.

Buster: A machine for cutting off the heads of rivets; also the edged tool which does the cutting.

Butt: To strike by thrusting; to join at the end. The thick, large, or blunt end of a timber or pile. The square end of a connecting rod.

Butt-end: Same as "Butt."

Butt Joint: A joint in which the ends of the pieces are square and press against each other.

Butt Riveting: The making of a butt-joint by using cross-plates and rivets.

Butt Splice: A splice formed by bringing the dressed square ends of two pieces of material together and joining them by welding or bolting or by riveting on plates or scabs.

Butt Strap: A steel attaching plate, used in timber construction, fastened to the outside of two abutting timbers.

Butt Weld, or Jump Weld: A weld in which the pieces are butted against each other and then joined by welding.

Button Head: The head of a bar, bolt, or rivet having the shape of a button.

Button-head Spike: Similar to "Barge Spike."

Button Set: A rivet set or snap, giving a button shape to the rivet head.

Buttress: A short cross-wall built against the main wall to increase its stability.

Butty Gang: A gang of workmen who take a contract for a part of any job.

Buzz Saw: A circular saw; so called from its sound when in action.

By-pass: An extra pipe passing around a valve or chamber to equalize pressure or to prevent a complete stoppage of the flow of the fluid.

By-product: A secondary or additional product from any manufacturing process.

By-wash: A channel cut to convey the surplus water from a reservoir or aqueduct, for the purpose of preventing overflow.