Mechanical Engineering Dictionary-Machine Components

Important Terms and their Meaning of Mechanical Engineering - Machine Components:

ANGLE PLATE – Right angled metal plate used to secure parts during machining or when taking measurements.

ANVIL – Heavy block on which to hammer and shape metals.

APRON – The function of a lathe apron is to carry the mechanism for sliding and surfacing motions and screw cutting.

BACK GEARS – Gears applied to machine tools to increase the number of speed changes obtainable with a cone or step pulley belt drive.

BASTERED THREAD – A screw thread which does not confirm to any recognized standard dimensions.

BED – One of the principal parts of a machine tool having accurately machined ways or bearing surfaces for supporting and aligning other movable parts of the machine.

BELLCHUCK – Hollow cylindrical chuck bolted to the main chuck for the purpose of giving additional support to work of awkward shape.

BELT SHIFTER – A flat hardwood strip of suitable length having shifter fingers attached at one end and used to shift a belt from one pulley to another or to replace a belt which has run off a pulley on an overhead drive shaft.

BOLSTER – Support for dies and tools in forging presses and drop stamps.

BOX ANGLE PLATE – An angle plate made of cast iron, usually with slots cast in it and accurately machined on the outside.

BOX JIG – A jig made in the form of a box into which the job to be drilled is inserted.

BULL WHEEL – The large gear wheel of a planer which meshes with the rack under the table and drives it. The large crank gear of a shaper is often called a bull wheel.

CAP SCREW – A finished screw, used for fastening two pieces together by passing the screw through a clearance hole in one part and screwing it into a tapped hole in the other. Heads may be hexagon, round, flat, fillister or socket type.

CARRIAGE – A principal part of lathe. The carriage carries the cutting tool and moves along the ways of the lathe. It contains the saddle, compound slide, and apron.

CARRIER – Tool for driving work which is held between centers, as in a lathe.

CATCH PLATE – Plate screwed to the nose of the lathe spindle for the purpose of driving work held between centers, through the medium of a carrier or driving dog.

CENTRE SQUARE – Device to enable the rapid location of the centre of the flat end of a cylindrical workpiece.

CHANGE GEARS – An assortment of gears which are supplied with a machine for changing speed ratio between driver and driven parts of the machine. Change gears on a lathe make it possible to cut threads of different pitches and obtain different feeds per revolution. On milling machines they are used to obtain different leads when milling spirals and helices.

CHUCK – Appliance for gripping tools, such as drills, or for holding work in a lathe.

CLAPPER BOX – A part of the shaper tool head that holds the tool post. A clapper block is hinged into the clapper box to permit the cutting tool to swing upward on the return stroke.

COLLET – Means of gripping a bar to give quicker chucking, particularly in capstan work for rapid and accurate setting.

CLAMP – Device for holding work during marking out, measuring, machining, fitting or grinding.

COMPOUND SLIDE – A principal part of a lathe, frequently called a COMPOUND REST, consisting of an upper and lower part dovetailed together. The lower part or base is graduated in degrees and can be swivelled to any angle for turning short tapers and angles. The upper slide carries the tool post and tool holder.

CONE PULLEY – A stepped pulley having two or more diameters and made in one piece.

DEAD CENTER – The center fitted to the tailstock of a lathe and so named because it does not rotate. Also the exact or precise center of an object.

DEMAGNETIZER – Device for removing permanent magnetism from steel tools and parts.

DIE HEAD – Device to enable small or medium sized work to be screwed in capstan or turret lathes. The die head consists of a cylindrical body with a shank to enable it to be clamped in the turret.

DIE SCREW – Tool used when threading cylindrical pieces beyond the capacity of a die plate.

DISTANCE BLOCK – Accurately ground steel block used to hold a component at a set distance from another surface, or to operate a trip mechanism tool when the tool carrier or worktable reaches the desired position.

DIVIDING HEAD – Indexing or dividing head is an attachment used on the milling machine table, for accurately dividing the circumferences of components for grooving or fluting, gear cutting, cutting of splines, squares or hexagons.

DOG – A tool or accessory which can be clamped on a workpiece to drive it while held between centers, as a lathe dog. Also, the name given to a projecting part on a machine tool which strikes and moves another part, such as the reversing dogs on a grinding machine or planer.

DRIFT PIN – A round tapered steel pin used to align rivet holes so that the rivet will pass through the holes easily.

DRILL ADAPTER – An attachment used to fit square shank drills and Morse taper sockets.

DRILL CHUCK – A self centering tool holding device, for driving drills and other such cutting tools in a drilling machine.

DRILL DRIFT – A wedge shaped piece of steel that is used to remove tapered shank tools, such as drills from spindles, sockets and sleeves.

DRILL HOLDER – An attachment used for holding drills in the turret of a capstan lathe.

DRILLING JIG – Device, usually of hardened steel plate, for holding a piece of work in a definite position, provided with guide bushes through which drills can pass so as to locate holes in exact positions in the work.

DRILL SLEEVE – A steel part tapered inside and outside which fits onto the tapered shank of a cutting tool, such as a drill or reamer, to adapt it to the size of the hole in the drill press spindle.

DRILL VISE – A work holding device in which the work is set and held while drilling and other operations are performed.

DRILL SOCKET – An adapter for holding taper shank drilling tools which have a taper shank larger than the taper hole in the drilling machine. One end is tapered outside to fit the drilling machine spindle hole while the opposite end has a larger taper hole to receive the cutting tool shank.

EXPANDING MANDREL – It is used to hold work on an internal diameter. It is similar in principle to a spring cullet. Three jaws are arranged to expand outward and clamp the work, as a tapered pin is forced inward.

FACE PLATE – Flat, slotted plate screwed on the nose of the lathe spindle, or bolted to a flange, to enable work to be machined which cannot be held in the chuck.

FEATHER – A sliding key sometimes called a spline, used to prevent a pulley, gear, or other part from turning on a shaft, but allows it to move lengthwise. The feather is usually fastened to the sliding piece.

FEED STOP – Method of tripping the power feed of a machine tool at a predetermined point.

FIXTURE – Device by which a component to be machined is correctly located and held during a machining operation.

FLASK – Complete moulding box that contains the sand that form the mould.

FOLLOWER REST – A support for long, rather small diameter work to be turned in the lathe. The rest is attached to the carriage and set close to the cutting tool. It travels along with the cutting tool to prevent the work from springing away from the cutting tool.

FOOT STOCK – Part of a dividing head attachment for the milling machine. It contains a center for supporting the workpiece, the same as the tailstock does for a lathe.

FOUR JAW CHUCK – A chuck that provides a more powerful grip on the work by means of four jaws which may be adjusted independently, so that irregular shapes may be gripped, and the fact that the jaws can be reversed enables the work to be gripped inside as well as from the outside.

GIB – An angular or wedge like strip of metal placed between two machine parts, usually sliding bearings to ensure a proper fit and provide adjustment for wear.

GOGGLES – These are worn when tool grinding, to protect the eyes from the flying particles of grit.

HALF NUT – A mechanism attached to the apron of a lathe and operated by a lever. The lever opens and closes a nut that has been split lengthwise so that the two halves of the nut can be closed upon the lead screw when threads are being cut. Also called SPLIT NUT.

HAND VICE – Small vice used for holding light articles such as pins, screws etc., especially during heat treatment.

HAND WHEEL – Any of the wheels found on machine tools for moving or positioning parts of a machine to hand feed, as the tailstock handwheel on a lathe.

HARDIE HOLE – Square hole in the face of an anvil which forms the location for the hardies and other tools used by the smith, such as small swages, fullers and cutters.

HEAD STOCK – An assembly containing the headstock spindle and the mechanism for driving it which is fastened permanently to the left end of the lathe bed.

HOLDING BLOCK – Fixture designed to hold small or thin gauge parts which cannot readily be held in a vice.

IDLER GEARS – A gear or gears placed between driver and driven gears when the distance between the driver and driven gears would require too exceptionally large gears. These gears have no effect on the speed or ratio between the driver and driven gears.

INDEPENDENT CHUCK – A three jaw chuck, in which each of, the jaws may be moved independently of the other two.

INDEX CRANK – The crank handle of an index or dividing head used for turning the spindle through a full turn or fractional part of a turn. A pin on the crank fits into the holes of the index plate.

INDEX PLATE – A thin circular plate having various circles of holes. It is attached to the index head and used for obtaining fractional parts of a turn of the index crank. A set of three or more index plates may be furnished for an index head.

INTERMEDIATE GEAR – An idler or loose gear on a stud for transmitting power between a driver and a driven gear.

JACOB’S CHUCK – Gear operated drill chuck of three jaw type for use on drilling or milling machines and lathes.

JACOB’S TAPERS – Standard system of tapers which are used for drill chucks and spindles.

JIG – A device that locates and holds a workpiece and guides the cutting tool.

JIG BUSH – Hardened steel cylindrical guide, made a press fit into the body of the jig for a drill or reamer to pass through.

JIG PLATE – Flat steel plate provided with a number of bushed holes and used to locate the drill when drilling a component.

JOURNAL BOX – A housing or support for a bearing which contains the journal of the shaft.

KEYS – Metal pieces of various designs which fit into a slot in a shaft and project above the shaft to fit into a mating slot in the center hole of a gear or pulley to provide a positive drive between the shaft and the gear or pulley.

KNEE – A principal part of a column and knee type milling machine which slides vertically on the column and carries the saddle and table.

LADLE – Receptacle used for transporting molten metal.

LATHE CARRIER– It is clamped on a bar and engaged with a projecting dog on the catch plate fitted to the lathe head stock. This enables the bar to revolve between the centres.

LATHE CENTERS – Solid steel pieces which have a tapered shank and 60° pointed end. A live center fits into the headstock spindle and a dead center fits into the tailstock spindle to support and provide bearing points for the work turned between centers.

LAYOUT PLATE – A smooth finished flat steel plate on which work and tools may be placed and used while laying out a job.

LEAD SCREW – Master screw used for cutting a screw thread in a lathe.

LIVE CENTER – A lathe center that fits into the headstock spindle and so named because it revolves.

LEVER – A simple machine for obtaining mechanical advantage. The lever consists of a rigid arm or bar pivoted or bearing on a point called the fulcrum and has a weight arm and a power arm.

LOCK NUT – A type of nut that is prevented from loosening under vibration. The locking action is accomplished by squeezing, gripping or jamming against the bolt threads.

LOOSE PULLEY – A pulley which turns freely on a shaft so that a belt can be shifted from the driving pulley to the loose pulley in order to stop a machine driven by an overhead belt drive.

MACHINE VICE – A work holding device used on machine tools to seat and hold work securely in position while machining is done.

MAGNETIC BLOCK – Laminated block for use in conjunction with a magnetic chuck.

MAGNETIC CHUCK – Magnetic device for holding work during machining and grinding.

MANDREL – A turned, hardened and accurately ground cylindrical bar or shaft or spindle, incorporating a slight taper, used for holding bored parts in a lathe while the outside surface is being turned.

MANDREL PRESS – Press for the purpose of fitting mandrels to the bore of the work.

MANIPULATOR – Fixture in which work is held for welding.

MILLING HEAD – An attachment or device for the milling machine to add to the range of operations for increasing production, versatility, and accuracy of the machine. A vertical attachment makes it possible to do vertical milling on a horizontal machine.

MITER GEARS – Bevel gears which have a center or pitch angle of 45°.

MORSE TAPER – Standard system of tapers widely used on lathes and drilling machines.

MULTIPLE THREAD SCREW – A screw with two or more threads cut around the periphery of the workpiece to provide an increased lead with a specified pitch.

NUT – A metal fastener of square, hexagon or other shape having an internal thread which screws onto a bolt, stud, or arbor.

NUT BOX MECHANISM – In a lathe it is used to engage and disengage the lead screw for thread cutting. This comprises a pair of half-nuts capable of sliding in vertical slides in or out of mesh with the lead screw.

OVERARMS – Adjustable supports for the end of a milling cutter arbor farthest from a milling machine spindle.

PARALLEL JAW VICE – Type of vice in which the gripping faces between the sliding and fixed jaws are always parallel, irrespective of the gap between them.

PILOT – A guide at the end of a counter-bore which fits freely into the drilled hole to hold and align the body of the counter-bore while cutting takes place.

PINION – The smallest of a pair of gears regardless of the size or type.

PIN VICE – Small vice with self centering jaws useful for gripping small rods, wires, drills and files.

PIPE THREAD – A 60° thread form having flattened crests and roots which are cut on a taper having 3/4 inch taper per foot. Pipe thread is used on piping and tubing.

PIPE VICE – Clamping device designed to hold work of tubular or circular section.

POWER ASSISTED CHUCKS – These are used where great holding power is required. These are operated with auxiliary power such as compressed air or oil pressure. Where simplicity of chucking is the first consideration, magnetic chucks are used.

PULLEY – A wheel having a plain or V groove rim over which a belt runs for the transmission of power from one shaft to another.

QUICK CHANGE GEARBOX – A cluster of gears on a machine tool arranged in such a way that a sliding gear can be moved by a lever to mesh with anyone of the gears in the cluster to obtain desired ratio of speeds, feeds or thread pitches.

QUICK RETURN MECHANISM – A mechanism on various machine tools to give a table, ram or other movable part a rapid movement during the return or non-cutting stroke.

QUILL – A hollow shaft that revolves on a solid shaft, carrying pulleys, gears or clutches. When the clutch is closed, the quill and shaft revolve together.

RACK – A straight metal strip having teeth that mesh with those of a gear to convert rotary motion into reciprocating motion or just the opposite.

RATCHET – A gear with triangular shaped teeth to be engaged by a pawl which gives it intermittent motion or locks it against backward movement.

RELIEVING ATTACHMENT – A device or mechanism fastened to the cross feed of a lathe to provide a reciprocating motion to the cutting tool, to obtain a clearance in the back of the cutting edges of the teeth when making taps, milling cutters or hobs.

REVERSE LEVER – A lever on the machine tool for changing the direction of some movable part such as the lead screw on a lathe.

REVOLVING LATHE CENTRE – It is fitted in the tailstock instead of the fixed type of loose head centre, in some cases, so that the high speeds of work revolutions become possible.

RIGHT HAND THREAD – A screw thread which advances into the mating part when turned clockwise or to the right.

RIVET – A one piece fastener consisting of a head and a body and used for fastening two or more pieces together by passing the body through a hole in each piece and then forming a second head on the body end. It cannot be removed except by taking off the head.

ROLLER STEADY – Type of steady fitted with roller points to support long or slender work in a lathe.

ROTARY TABLE – An attachment for the milling machine consisting of a round work holding table provided with T slots and operated by a handwheel attached to a worm or worm gear for rotating the table. A scale graduated in degrees permits the work to be moved any number of degrees for spacing holes or milling radii. Also called CIRCULAR MILLING ATTACHMENT.

SCREW – A helix formed or cut on a cylindrical surface which may advance along the axis to the right or left. The helix may be single or multiple.

SCREW JACK – Device used for lifting a heavy load by means of a screw.

SCREW THREAD – A ridge of uniform section or shape in the form of a helix on the external or internal surface of a cylinder, or in the form of a conical spiral on the external or internal surface of a cone.

SELF CENTERING CHUCK – Design of chuck for holding hexagonal or cylindrical work, operating in such a way that the work is automatically centered.

SET SCREW – Usually a hardened steel screw having either no head or a square head and with various designs of points or ends to lock or tighten adjustable machine parts in position on a shaft.

SHOULDER SCREW – A screw having two or more diameters or shoulders and commonly used for supporting levers and other machine parts that have to operate freely. The screw body is slightly longer than the thickness of the piece pivoted on the screw so as to allow the piece to move freely when the screw is set up tightly against the bottom of the shoulder.

SLEEVE – A round piece of metal having a straight or tapered hole which fits over or into another piece to adapt parts to fit, as a taper sleeve for a lathe center.

SLIDE REST – A tool holding slide used on machine tools. It is usually adjustable for holding and guiding cutting tools. The compound slide or rest used on an engine lathe is an example. The compound slide permits the tool to be fed at any angle.

SLIDING TABLE (compound) – Device to enable holes to be drilled or bored very accurately with respect to each other.

SNAP FLASK – Strongly constructed wooden moulding box, split diagonally with hinges on one corner and locking latches on the opposite corner, so that the box may be removed from the mould prior to casting.

SOCKET HEAD – Screw threads having a hexagonal or other form of recessed socket in the head so that the screw can be turned with a wrench or key, as a hexagonal key.

SPLINES – Multiple keys cut in either a shaft or a hole of parts that are made to slide or move lengthwise on a shaft, as a sliding gear transmission.

SPLIT NUT – A nut which has been cut length wise so as to open for quick adjustment.

SPRING COLLETS – A type of draw in collet made of hardened steel and having three slots or saw cuts which permit the collet to be closed tightly against a tapered sleeve by the draw bar.

SQUARE THREAD – A form of screw thread in which the cross-section of the thread forms a square, making the width of the thread equal to the width of the space between the threads.

STAKE – Small anvil used for sheet metal work.

STEADY REST – A support attached to the ways of a lathe for turning long work pieces. Used to prevent slender work from springing away from the cutting tools or to permit machining operations to be performed on the end of the workpiece. Sometimes called a center rest or STEADY.

STEP BLOCK – A block of steel or cast iron having a series of steps and used for supporting the ends of machine clamps when clamping work to the table.

STEPPED CONE PULLEY – A cone pulley having several diameters or steps for obtaining different speeds on machine tools.

STOPS – Devices attached to the movable table or ram or parts of a machine tool, such as a milling machine table, to limit the amount of travel.

STUD – A plain cylindrical piece having a threaded portion of suitable length at each end or a continuous thread over the entire length. One end is screwed into a machine or workpiece after which a second part is placed over the stud and held in place by a nut.

SWIVEL SLIDE – Device to enable the toolpost slide of a lathe to be set at an angle for taper turning or cutting V threads.

SWIVEL VICE – A bench or machine vice for holding workpiece which may be rotated on its base to the desired angle or position.

TABLE (marking off) – Table used for marking off, or setting out a job to be machined.

TAILSTOCK – The principal part of the engine lathe, used for supporting one end of a workpiece by means of a center point held in the spindle. May be moved along the ways and clamped in different positions and offset from the true axis of the lathe for turning tapers.

TAPER PINS – Steel pins used for locating and holding machine parts in position on a shaft.

TAPER TURNING ATTACHMENT – Device fitted to a lathe, to cause movement of cutting tool at an angle to the axis of the lathe so as to produce the required taper on the workpiece.

TAYLOR CHUCK – Special chuck designed so that the jaws are supported at right angles to the direction of the pressure.

T-BOLT – A threaded bolt having a square or rectangular end which fits into the T slot of a machine table for clamping work-pieces.

THREAD CHASING DIAL – A device consisting of a short shaft with a dial at the top and a worm gear at the bottom to mesh with the lead screw on an engine lathe which is attached to the lathe carriage, so that the operator can engage the split nut lever at the correct position when cutting screw threads.

THREE JAW CHUCK – Chuck for gripping general work using three jaws, usually concentrically, simultaneously, a feature which makes the chuck particularly suitable for holding either round or hexagon stock.

THUMB SCREW – A type of screw having a winged or knurled head for turning by hand when a quick and light clamping effect is desired.

TOOL HEAD – The part of machine tool that carries the cutting tool and is adjustable for moving and setting the cutting tool into the workpiece being machined.

TOOL HOLDER – Slotted shank in which the tool bit can be held.

TOOL POST – A clamping device for holding tool holder in position on a machine tool.

TOP SLIDE – Means of traversing the tool on the tool post of a lathe.

T-SLOT – A recessed or undercut slot made with a special T shaped cutter in the tables of machine tools to receive the square head of a T bolt for clamping work-pieces.

TUMBLER GEARS – Two gears acting as idler gears between the spindle gear and the fixed stud gear on a lathe gear train. Used to reverse the direction of rotation of the lead screw for thread cutting or the feed rod for turning.

TURRET – Rotatable device for holding several cutting tools set in position to operate in turn.

TWO JAW CHUCK – Chuck furnished with two jaws, diametrically opposite.

U-BOLT – An externally threaded fastener bent in the shape of the letter U and with both ends threaded.

U-CLAMP – A flat or square piece of metal bent or formed into the shape of the letter U and used for clamping work-pieces on a machine table.

UNIVERSAL CHUCK – Design of chuck in which the jaws are moved simultaneously by gear wheels, by a scroll or by a combination of both. Also called concentric chuck or self centering chuck.

UNIVERSAL INDEX CENTERS – A dividing head and foot stock with a set of change gears to gear the spindle of the index head to the index crank for differential indexing, and to gear the index head to the lead-screw of the table of a milling machine for helical milling.

UNIVERSAL VICE – A work holding device usually used on the milling machine which has either two or three swivel settings so that work-pieces may be set at any desired angle including compound angles.

V-BLOCK – Block of metal having a V-shaped groove cut in its top surface in which can rest a circular shaft.

V-SUPPORT – Steady in the form of a V, to support the work near the cutting tool.

VICE – A mechanical device of many designs and sizes in which work-pieces are clamped for hand and machine operations.

VICE CLAMP – Piece of soft material so shaped as to enable it to fit over each of the hardened jaws of a vice in order that work-pieces may be gripped without damage.

V-WAYS – The top part of the bed of a lathe, planer or other machine bed which acts as a bearing surface for aligning and guiding the moving parts, such as the carriage of a lathe.

WAYS – The flat or V shaped bearing surfaces on machine tools over which other movable parts slide.

WOODRUFF KEY – A flat semicircular piece of metal used as a key in a special circular key seat slot cut in a shaft to drive a gear, pulley or other part.

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