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Glossary of Bridge Terminology



Nail: A slender piece of metal either pointed or tapering, used for driving through wood or other material. Nails run in size from 2d (two penny), one inch long, to 20d (twenty penny), four inches long in carpenter usage. Bridgemen use nails up to 60d (sixty penny), or six inches long, after that they are classed as spikes.

Nail-extractor: A hand-tool for pulling nails.

Nail-head Spike: A spike having a long, slim, square shank and a flat, square head.

Nailing-blocks: Blocks of wood inserted in walls of stone, brick, or concrete for nailing boards to.

Name Plate: A plate attached to a bridge showing the names of the designer, fabricator, and erector. Sometimes other names are added.

Naperian Logarithm: Same as "Hyperbolic Logarithm." -- A system of logarithms in which the base is 2.71828+

Nasmyth's Steam Hammer: The earliest form of steam hammer-invented by Nasmyth and Bourdon. Its essentials are a steam cylinder, piston, piston rod carrying a heavy weight for hammer, pile cap and a frame of two I-beams holding the parts together.

Natural Bar: A bar of sand or gravel formed in a river bed by the usual physical process of precipitation.

Natural Bed: The bed of a stone as it lay in the quarry.

Natural Cement: Formerly a pulverized stone which, without having heat applied, acquired the property of hardening under water. The term is now applied to a cement made from natural rock (containing the required constituents in approximately uniform proportions) by calcining and grinding.

Natural Logarithm: Same as "Hyperbolic Logarithm." -- A system of logarithms in which the base is 2.71828+

Natural Scale: A full-sized delineation of an object. Sometimes used for "Unexaggerated Scale."

Nave: The hub of a wheel.

Neat: Pure; undiluted; unadulterated. Also sometimes used for "Net."

Neat Briquette: Same as "Cement Briquette." -- A briquette made of cement and water for testing the tensile strength of the cement.

Neat Cement: Pure cement without the addition of sand, gravel, or rock.

Neat Lime: Lime mixed with water and used for plastering or whitewashing.

Neat Line: The true face line of a building regardless of the projections of the stones. A line back of or inside of incidental projections.

Neat Work: The work or part of construction inside of the "neat line."

Neck: That part of a test specimen, subjected to tension, which shows a reduction of area of cross-section when the ultimate load is reached. To reduce suddenly the sectional area of a piece of metal. To nick.

Neck Journal: A journal having a smaller diameter than that of the main part of the shaft.

Necking-down: The act of reducing the cross-section of a test specimen by stressing it beyond the yield point.

Needle: A very small steel rod or bar.

Needle Beam: A cross-beam supporting a load, used in underpinning walls.

Negative Moment: A relative term used to denote direction of rotation, usually taken counter-clockwise.

Negative Print: An intermediate print from which the final or positive print is made.

Negative Reaction: A reaction caused by an uplift, and therefore acting in an opposite direction to a reaction caused by a direct load.

Negative Rotation: Rotation in a direction opposite to that of the hands of a clock.

Negative Shear: A relative term usually applied to a shear producing a downward motion.

Nest (of rollers): A group of rollers, enclosed in a suitable frame or box, which support a bridge shoe.

Net: Clear of anything extraneous. Lowest or smallest. Not subject to any further deduction or correction. Netting.

Net Section: Used improperly for the net area of a section; i.e., the available area of a member after the rivet-hole areas are deducted.

Netting: A wire mesh-work used somewhat in reinforced-concrete construction, especially for piling.

Neutral Axis: The trace of that plane in a beam where there is no tension or compression and where no deformation takes place.

Neutral Curve: The curve of the neutral axis of a loaded beam.

New York Rod: A level rod having two sliding parts and a movable target. It is engine-divided into feet and decimal parts thereof. The graduations are fine lines burned into the hard wood and can be read direct only for very short sights, thus necessitating the setting of the target. This rod is used for precise work.

Newel Post: The principal post at the angles or at the foot of a stairway.

Nickel Steel: Steel containing from three per cent to five per cent of nickel and from two-tenths to one-half per cent of carbon. The addition of the nickel increases the strength and the elastic limit of the metal.

Nidged Dressing or Nigged Dressing: In stonework a finish picked with a pointed hammer or cavil.

Nidging or Nigging: A form of stone dressing."

Niggerhead: A spool on the end of the axle of a hoisting engine.

Night Foreman: A foreman who directs the work of a night shift.

Night Superintendent: The person in complete control of work during the night.

Nipper: A block which slides in the leads of a pile driver and carries a pair of hooks or tongs for picking up the hammer below it.

Nipper Pile Driver: A pile driver in which a nipper is used for engaging the hammer during lifting. It is tripped at the top of the leads.

Nipple: A short piece of pipe threaded throughout its entire length.

Nodule: A small lump.

Nominal Horsepower: Same as "Commercial Horsepower."-- Horsepower calculated from the area of the piston. Sometimes only a fraction of the real horsepower.

Non-concurrent: Applied to non-parallel forces not having a common point of intersection.

Non-fusibility: The ability to resist fusing.

Non-volatile Thinner: That portion of the thinner which is not volatilized by a current of steam at atmospheric pressure.

Non-volatile Vehicle: The liquid portion of a paint, excepting only its volatile thinner and water.

Normal Stress: A stress which acts at right angles to a plane in the interior of a body.

Norway Iron: A very pure wrought iron manufactured in Norway, used in making hooks for blocks, etc.

Norway Pine: A variety of pine tree of large size. The wood is largely sap-wood and not durable. Grows in small scattering groves.

Nose: A pointed or tapering projection in front of an object., e.g., the nose of a pier that acts as an ice-break.

Nosing: The end of a pier. See also "Starling." The projection on the front edge of a step.

Notching: Cutting into a timber so that it will fit over another. Nicking.

Nozzle or Nozle: A short pipe or tube with a contracted opening.

Nurick Column: Same as the Keystone Column (A structural steel column made of four bent channels riveted together, with thimbles or nipples over the rivets separating the channels) with the nipples or sleeves omitted.

Nut: A short prism of metal having a central hole which is threaded to receive a bolt or a screw.

Nut-cracker: A tool for breaking the nuts on rusty bolts.

Nut Lock: A device for preventing a nut from turning.