Engineering Design Concepts, Drawings, Measurements and Marking Out

Section Three Measurement, Comparison

and Marking Out Tools

Vocational Education and Training MEM05v11 Metal & Engineering Cert 1, 2 & 3

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TABLE OF CONTENTS SECTION THREE MEASUREMENT, COMPARISON AND MARKING OUT TOOLS Section Learning Objectives Page 4 Section Introduction Page 4 History of Measurements Page 5 Measuring Tools Page 6 Fixed Gauges Page 15 Marking Out Tools Page 20 Care and Maintenance of Measurement and Marking Out Tools Page 33 Section Summary Page 41

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SECTION 3 – MEASUREMENT, COMPARISON AND MARKING OUT TOOLS WHAT OUTCOME CAN YOU EXPECT FROM THIS SECTION? In this section you will learn how to identify basic measurement and marking out tools. SECTION LEARNING OBJECTIVES On completion of this section you will learn:

The history of measurement What the common measurement tools are What the common fixed gauge tools are What the common marking out tools are About the maintenance care and storage of these tools

SECTION INTRODUCTION This section is designed to give you a good appreciation on the various types of hand tools commonly used for measurement, comparison and marking out. Emphasis is not placed on highly automated or technically advanced tools, but rather to let you understand the uses of common hand measurement tools as well as simple marking out tools. Marking out or layout is the process of transferring a design or pattern to materials or work piece, as the first step in the manufacturing process. In the metal trades area, marking out consists of transferring the dimensions from the plan to the work piece in preparation for the next step, machining, welding, fabrication or manufacture. Many of the tools reviewed in this section are used in the ‘marking out’ process. Measurement tools may be used in marking out but also in the measurement of the final product, inspection sampling or in between manufacturing processes. The term ‘comparison tools’ means the ability to compare a final product with a fixed measurement tool, template, sample, prototype, jig, etc, to ensure it meets specification. It could be as simple as a tape measure to a sophisticated template or test jig.

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HISTORY OF MEASUREMENTS The ‘cubic’ developed by the Greeks - the length of a man's forearm or the distance from the tip of the elbow to the end of his middle finger was considered the first widely accepted measurement. Later the Romans established their own measurement system closely modelled after the Greek cubic. What is now called an ‘inch’ originally was the width of a man's thumb. They found that twelve ‘inches’ closely equalled the length of a man’s foot and three ‘foots’ closely equalled the distance between the end of the outstretched arm and their chin then called a ‘yard’. The Romans did not use the cubic in their calculations. The only problem with this measurement system was that body shapes were not the same so measurements could widely vary. The French created a standard unit of measurement called the metric system in 1790. This is today's international system of unit for measurement although some countries still use a system based on ‘inches’, ’feet’, ‘yards’ and ‘miles’ as their common system (USA being one) but use the metric system when needing to meet international engineering standards.

Simply, it is based on the ‘decimal system (units of ten). The ‘metre’ is the starting point and the other measurements were set up in decimal ratios with the metre. 1 metre = 100 centimetres 1 centimetre = 10 millimetres 1 metre = 1000 millimetres 1 kilometre = 1000 metres ....and so on.

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MEASURING TOOLS In this section we look at measuring tools that measure dimensions. In some applications such as metal casting there are measuring tools that measure volume, weight and temperature. CALLIPERS Callipers are the very simple tools used together with a steel rule for the measurement or comparison of linear dimensions. An experienced worker can achieve +/-0.05mm in the measurement. Callipers are classified into two types: Outside Callipers - Outside callipers are used for measuring external dimensions such as the length, diameter, or even the thickness of a solid. Inside Callipers - Inside callipers are used for measuring internal dimensions such as the diameter of a hole, or the width of a slot etc.

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VERNIER CALLIPERS Vernier Callipers are more precise tools capable for measuring external dimensions, internal dimensions, and depths. Besides the two pairs of measuring jaws and the depth gauge, its main features also include a main scale and a Vernier scale. Further refinement to the Vernier calliper is the dial calliper. In this instrument, a small gear rack drives a pointer on a circular dial. Typically, the pointer rotates 1 millimetre, allowing for a direct reading without the need to read a Vernier scale (although one still needs to add the basic tens of millimetres value read from the slide of the calliper).

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VERNIER HEIGHT GAUGE A Vernier height gauge is used for measuring height of an object or for marking lines onto an object of given distance from a datum base (base line).

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MICROMETER A micrometer is a more precise measuring instrument than the Vernier callipers. The accuracy comes from the fine thread on the screw spindle. The ratchet prevents excess force from being applied. Generally, the screw spindle has a pitch of 0.5mm. The thimble is divided into 50 equal divisions. The three common types of micrometers used in the workshops are: Outside Micrometer - An outside micrometer is used for measuring external dimensions. The work to be measured is placed between the anvil and the tip of the spindle. Inside Micrometer - This is similar in structure to an outside micrometer and is used for measuring internal dimensions. Depth Micrometer - A depth micrometer is used for measuring the depth of a hole, slot and keyway, etc. A complete set of depth micrometer is equipped with spindles of different lengths, which can be interchanged to suit different measuring ranges.

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PROTRACTOR The protractor is a general purpose tool used for the measuring / checking of angles such as the angle of drill head, angle of cutting tool, and even for the marking out of angles on a component part. Bevel Protractor - The universal bevel protractor is designed for precision measuring and layout of angles. This is a precision measuring tool that the accuracy of measurement can reach 5 minutes of an angle through the Vernier scale.

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DIAL GAUGE A ‘dial gauge’ gauges an object for any deviation within a certain range. An example could be a shaft in a lathe being gauged for straightness. This deviation is usually shown in units of measurement, but some gauges show only whether the deviation is within a certain range. The accuracy of dial indicator can be up to 0.001mm. It is usually used by fitters and turners to align work on machines.

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STEEL RULES Steel rules, also called rulers, are essential in any shop when accuracy matters. Steel rules are inherently more accurate than folding rules because they are made in one piece. Steel rules come in rigid and flexible versions. While their primary purpose is accurate measurement, they can also be used as guides for laying out lines (called straight edges). The thinner, more flexible rules can also be used to measure rounded or cambered work. A narrow rule is used to measure the depth of narrow slots and small diameter holes where the standard rule is too wide to be used. Most rules are made by cutting the required length from a roll of band spring steel, with etched graduations. Rules made by this method are adequate for most applications and reasonably priced. Higher-priced rules are cut, not stamped, from plate steel and the edges are ground. Graduations are machined, much deeper than etched graduations, longer-lasting and easier to read in poor light.

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TAPE MEASURES A tape measure or measuring tape is a flexible form of rule. The flexible steel tape is housed in a metal casing with a spring attachment, which retracts the tape into the casing when the end is released. This type of rule is best because of its compactness and suitability for taking inside measurements. The tip of the tape is riveted in place and slides slightly; the length of the slide is the same as the thickness of the tip, to allow the user to make accurate measurements. With a sliding tip you get the same measurement hooking the end of the tape over a piece of material or butting the tip into a corner.

Butting up On edge

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COMBINATION SET A combination set is a set of equipment combining the functions of protractor, engineer square, steel rule, centre finder, level rule, and scriber. A combination set square is a useful and accurate tool which has many uses:

rule or straight edge square and 45 degree mitre gauge depth or height gauge protractor gauge centre finding gauge spirit level

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FIXED GAUGES A quick, simple, cost effective method of checking product was needed as a result of the industrial revolution and batch type production. Assembly line concepts required ease of use, little to no training and ‘fixed limit gauges’ were the answer to this need. When manufacturing undertakes to produce a complex assembly, usually involving many components, it is generally more economical to assign the production to specialised departments, and in some cases, other manufacturing plants and/or subcontractors, where machinery, equipment and specialised skills are available. This allows large numbers of manufactured parts to be stock piled at the assembly plant without having to be test fitted or customised. Gauging components separately, make it possible to select any part in stock and know they would fit together in a fully functioning assembled unit. Fixed limit gauging, therefore, became an integral part of the process. Machine operators, working on parts with critical dimensions were provided with gauges so they could keep a ‘real time’ check on the wearing of tools, and other problems which cause deviations in the production process. Also, identical parts made at other plants could be checked to ensure that no matter what manufacturing facility made the part, they would all be identical. Gauges tend to be quicker and easier to use because they are designed for more specific tasks. And because gages are designed for use over a shorter range of dimensions, they tend to be capable of generating results of higher accuracy. Therefore, gages are usually the practical choice for high-volume parts inspection, particularly where high precision is needed.

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TYPES OF FIXED GAUGES There are numerous types of standard fixed gauges. Many of these can be purchased in sets and used for a wide range of inspection and testing jobs. Some include:

Cylindrical gauges Angle gauges Thread gauges Radius gauges

....and so on. The most common fixed gauges can be broken down into two basic configurations, those used to inspect the inside diameter of parts (ID’s) and those used to inspect the outside diameter of parts (OD’s). Within these two broad configurations there are at least two additional significant categories of fixed gauges, cylindrical and threaded. There are fixed limit gauges for other applications such as groove widths or depths, and lengths. Cylindrical plug gauges are used to check hole diameters. The style or type may vary because of size or manufacturer, but the basic concept of deciding gauge size and tolerance is universal for cylindrical gauges. The concept is to have two gauges, one at each end of the product tolerance or limits. If the diameter being inspected is 'in size', (made to the product specifications) the smaller or 'Go' gauge will easily enter the hole, while the larger or 'NoGo' gauge will not enter the hole. The Go gauge has a PLUS tolerance and the NoGo has a MINUS tolerance. This gauge will not tell us the size of the hole, but it will tell us if the hole is correct or incorrect, making it quick and easy to accept or reject a part.

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The other cylindrical gauge is for checking the outside diameter of parts such as shafts. The Go/NoGo tolerances are opposite to the plug Go/NoGo gauges. The Go gauge has a MINUS tolerance and the NoGo has a PLUS tolerance. Angle gauges or angle blocks are two solid plates positioned at an angle and where a part is positioned next to the angle block to check the angle meets specification. Almost always an angle block is used in conjunction with a ‘surface plate’, a solid steel or cast iron plate where the surface has been machined precisely flat. Height gauges are also commonly used with angle blocks.

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Thread gauges are dimensional tools for measuring and/or verifying thread size, pitch or other parameters. Thread gauges are used for external threads and internally tapped threads. Radius gauges as the name implies are used to check radius in parts both outside radius and inside radius.

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Operators of machine tools such as lathes would likely use gauges to check the machine tool wear. There are gauges that check the proper angle when sharpening tools such as drill bits, boring head, surface milling heads and so on.

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MARKING OUT TOOLS Marking out or layout is the process of transferring a design to a work piece, as the first step in the manufacturing process. The work piece may be a paper, cardboard, wooden or metal template or it may be transferring the design or pattern directly to some type of material. We look at the common types of marking out tools. These include:

Chalk sticks Chalk strings Mark out blue dye Straight edges Steel rules Chord rule Tape measures Protractor Flexi curve Engineer’s try squares Bevel squares Combination square Centre square Scribers Scribing block Punches – centre, prick Dividers – common, odd leg Trammels Surface tables Ball peen hammers

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CHALK STICKS Chalk sticks (also known as engineer’s chalk) are not actually chalk as you would use on a blackboard. The stick is made of soapstone or a mixture of talcum and wax. It is stronger than normal chalk sticks and can be sharpened to a fine point or edge. It leaves a waxy semi-permanent mark. It shows up well on the darker surfaces of steel, can be wiped off if a mistake is made but is somewhat susceptible to washing away. It is used by welders as it is easily seen under a welding helmet when welding. It comes in flat sticks, round sticks and squares approximately 10mm by 10mm. CHALK STRINGS Chalk string line is a chalk filled tool that coats string with chalk dust as it is pulled out of the container. It is used for marking out large jobs. Pull the required length of string from its container and it is ready to use. A helper holds one end on the required mark out position and pulls it tight over the other mark out position. A person then lifts the string straight up and releases. A straight chalk dust line will be transferred from the string to the job.

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MARK OUT BLUE DYE Blue dye (also known as engineer’s blue or layout dye) is used to clearly identify straight lines. It is applied like paint (brushed or sprayed) to the material and allowed to dry. Lines can be scratched into it using a scriber and be easily seen. Often used on sheet metal, small parts, round bar and shiny materials where chalk lines are harder to apply and see. STRAIGHT EDGES As the name implies a straight edge is a flat length of steel with a straight edge. It is similar to a steel rule but has no measurements. Lay the tool along an edge to check that the edge is straight. Use it to draw a straight line between join two points. Some straight edges are flat steel bars milled to a straight edge and others are tube like.

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RULES A stainless steel rule is a long straight edged tool, available in different lengths, used to mark out straight lines and measure lengths. It has graduated measurement marks along its length. The most common sizes are 150mm, 300mm and 1 metre. CHORD RULE A chord rule can be used with a set of dividers to measure angles (from 0 to 120 degrees in 1/2 degree angles) and to determine the circumference of a circle from a diameter measurement. A chord rule has two blades; one side is sub divided into millimetres and a line of chords scale, and the other is subdivided into millimetres and a circumference scale. There are two centre dots on each blade and dividers can be used in these to set the blades between two points. The angle can be measured if this distance is a chord or a circumference measurement and can be read if this distance is a diameter. It is often used where circumference measurements are required without calculation or where angular measurement is needed.

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TAPE MEASURES A tape measure or measuring tape is a flexible form of rule. The flexible steel tape is housed in a metal casing with a spring attachment, which retracts the tape into the casing when the end is released. This type of rule is best because of its compactness and suitability for taking inside measurements. The most common lengths are 3m, 5m and 8m but longer ones are available. The accuracy of a measuring tape is plus or minus 0.5mm.

PROTRACTOR A protractor, or half circle, is used for measuring or marking off angles of less than 180 degrees. It is divided into 180 equal parts. Each division is one degree. Most measurements or layouts requiring a protractor are performed using a combination square.

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FLEXI CURVE A flexi curve (also known as a flexible curve) is a flexible drawing tool that can be moulded to any curve or contour. It is usually made from lead which is wrapped in steel ribbons, and covered in plastic. To use it a person simply bends the flexi curve to the desired shape and draws along the edge. It is used to draw curves by connecting points laid out on a work piece. ENGINEER’S TRY SQUARES A try square is used for marking, measuring and checking the accuracy of right angles (90 degrees). It has a metal ruler set at right angles to another straight piece. A traditional try square has a broad blade of steel or brass riveted to the face of a wooden handle called the stock. This is added to the stock to ensure a straight edge. Engineer’s try squares are also known as an engineer’s square or a machinist square.

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BEVEL SQUARES This tool is also known as a sliding bevel, angle bevel, bevel square, sliding T-bevel, or adjustable try square. Tongues range from 150 mm upward, sometimes to 450 mm. Whatever the length of the blade, the stock is always shorter. The tongue of the bevel gauge fits into a groove cut into the head of the stock. In most models, a slot cut into the tongue allows further adjustments of the position of tongue and stock. The tongue is usually made of thin steel and the stock of wood, plastic, or metal. The bevel square is a marking out tool used to transfer a known angle to the material. It is adjustable from 0 to 180 degrees. COMBINATION SQUARE A combination square is part of a combination set. It consists of a square and a rule and can be used to check components for square or marking lines when marking out. One edge is at 45 degrees; the other is at 90 degrees. The rule is also useful for measuring and checking depths.

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CENTRE SQUARE The centre square is part of a combination set. It consists of a centre head and a steel rule. To use a person places the centre head against a circular component and scribes a line through the centre of the component using a scriber and the attached rule. Then repeats at 90° to the previous line. The centre of the circular component is where these two lines cross. SCRIBERS Scribers are used to lay out lines on steel and other metals. The scriber point scribes sharp, well defined lines on the materials. Single point pocket-type scribers have a scriber point made of tempered high grade steel and a handle of stainless steel tubing. In many cases the point is reversible, telescoping into the knurled handle when not in use. Bent point scribers are usually with one straight point, and one long or one short bent point. Some of these scribers are threaded and can be engaged in either end of the handle. The long bent point is designed for reaching through holes beyond a lip or ridge.

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SCRIBING BLOCK A scribing block is a tool with an adjustment mechanism of the needle point height. A scribing block is used for marking out lines parallel to a datum surface or datum edge. It is also used as a dial gauge when a micrometre dial is installed replacing the scriber. CENTRE PUNCH A centre punch is a hardened long slender tool that is machined and ground to a conical point of 90 degrees. It is used to produce a 90 degrees dent on the surface of material to start a drill hole or as the centre of a circle to be marked with a pair of dividers. The indentation created by the centre punch prevents drill bits or divider points from slipping off the marked point.

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PRICK PUNCH A prick punch is a hardened, long, slender tool that is machined and ground to a conical point of 60 degrees. A prick punch is primarily used for the purposes of marking out. It produces a smaller indentation than a centre punch, which acts as a useful datum point in marking out operations. When layout is complete, the indentation made with a prick punch can be enlarged with a centre punch to allow for drilling.

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DIVIDERS Common engineering dividers are used for marking circles on material and for geometric development. They are similar to a drawing compass but instead of one point and a pencil they have two scriber points. Often they are used in conjunction with centre punches. Another type of divider is the ‘odd leg’ divider. These are generally used to scribe a line a set distance from the edge of the work piece. The bent leg is used to run along the work piece edge while the scriber makes its mark at a predetermined distance, this ensures a line parallel to the edge.

Common Divider

Odd leg Divider

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TRAMMELS Trammels are very large dividers with a beam, generally timber or aluminium, and two scribers and mounts. The scribers clamp to the beam at the required centre distance. The scribers are clamped to the beam at the required centre distance and the other scriber placed in the centre punch mark and then a large circle is scribed. It is used when a circle with a large radius is required. SURFACE TABLES Surface tables are tables that have a surface precision machined to provide a very flat surface. This is especially important for marking out items that require an accurate datum surface. They come in all sizes and are either steel, cast iron or granite surfaces.

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BALL PEEN HAMMERS In marking out, ball peen hammers are used for centre and prick punching. They come a wide range of sizes.

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CARE AND MAINTENANCE OF MEASUREMENT AND MARKING OUT TOOLS Most measuring tools as well as marking out tools are considered precision tools. They can be expensive and therefore they need to be used and maintained accordingly. Improperly maintained measuring and marking out tools not only mean increased replacement costs but also could affect the quality of the work being done. In some cases unmaintained tools can also be a safety hazard. PROPER USE The first rule with all tools including precision tools is to use the tool for the purposes it was designed for. Reading of user manuals and proper training is important. Precision measuring tools should not be used as substitutes for other tools. This will lead to the loss of accuracy of precision measuring tools. So it is not advisable to use Vernier calliper as line markers, micrometers as small hammers or a straight edge as a pry bar. These tools are not toys. Never put precision measuring tools together with hand tools, such cutting tools as files, hammers and drills for the fear of bumping the precision measuring tools. Never put them on lathes either to prevent them from dropping from lathes and breaking down due to vibration of lathes, especially in the case of Vernier callipers which should be laid flat in specific cases to avoid distortion.

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MAINTENANCE Certain marking out tools require sharpening including scribers, trammel points and punches. Both scribers and punches are made of hardened steel. When sharpening, care should be taken to avoid overheating the tips as this will remove the hardness of the steel. When sharpening punches, the tip angles should be maintained – 60 degrees for prick punches and 90 degrees for centre punches. For safety reasons punches should be clean and free from oils or grease to avoid slipping when being hit. Also it is advisable to wear eye protection when using punches. All squares, rules and straight edges should be checked for damage on edges. Damaged edges such as burrs and nicks make marking out difficult and sometimes impossible if the damage is too great. Squares, rules and straight edges should be checked regularly for straightness and flatness. Before and after use squares, rules and straight edges should be cleaned, removing any dirt or dust. It is recommended that a light coating of rust preventive oil should be applied to tools such as squares, straight edges, rules and so on. Try squares, in which the stock is loose, should be discarded and replaced. They are virtually impossible to repair.

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Tape measures require little maintenance except to ensure the tape itself is clean and the tip of the tape measure slides freely. Tape measures should be retracted slowly. This prevents damage to the tip and also prevents fingers or hands from being cut by the rapidly moving steel tape. Surface or marking out tables should be used only for inspection or marking out purposes only. Before use the surface should be cleaned and checked for any surface imperfections or damage. Smaller tables should be covered when not in use.

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Divider tips may need sharpening once in awhile and again, care should be taken to not overheat the tips when sharpening. The hinge and adjustment screws may need tightening and a spot of lubricant every so often. Callipers should be kept clean and avoid dropping them, as this can cause small nicks that will affect the accuracy of the tool. A light coating of rust prevention oil is recommended. Callipers with measurement markings may need to be cleaned often to prevent a build up of dirt or dust in the measurement markings. Protractors like callipers need to be used gently and kept clean.

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Ball peen hammers which are used for marking out should be used only for such purposes. Hammer handles should be tight and the face of the hammer head should be flat and free of burrs or major indentations. The grip of the handle should be free from oil to prevent slipping when being used.

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Vernier callipers, Vernier height gauges, micrometres and dial gauges are high precision tools and require the most care when using. Measuring faces of these tools must be kept clean and free from any damage whatsoever. Vibration from machine tools such as lathes, milling machines and drills can adversely affect the calibration of the tool. When not in use they should be placed in a vibration free location. They must be laid down in a location where other tools cannot bump into them or fall on top. Precision measuring tools should never be put near a magnetic area, such as a magnetic worktable, to avoid being magnetised. When damage is found on a precision measuring tool, such as unsmooth surface, burr, rusts, distortion of the body or ineffective movements, users should not be allowed to fix it on their own.. Users should send the faulty tool to a reputable repair shop and only use it after it has been properly repaired. Precision tools should be sent to authorised calibration facilities periodically to be tested and calibrated to avoid troubles with product quality caused by faulty reading errors of the tools.

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STORAGE Many precision tools come with storage boxes. These are supplied to prevent any damage occurring to the tools when not in use. These boxes should be stored in a location away from the production general tools and away from the production floor. This will prevent personnel using the tool for purposes that the tool was not designed for.

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At times it is recommended that these types of tools are stored in a locked cabinet accessible only to those authorised and trained to use such tools. These tools can be expensive, so locking them up will prevent loss as well. The storage area should be in a location away from major temperature swings, dry and dust free. Items including squares, straight edges and rules should be laid flat to avoid slight warping or bending.

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SECTION SUMMARY The engineering and metals industries rely heavily on measurement tools. Today technology has made these tools easier to use and far more accurate. Some tools now have digital read outs replacing the graduation marks and the dials. Others allow direct readouts and inputs into computers and computerised machinery. In this section we review only the basic and most common measurement tools and those tools used for marking out. In the next section we review the common and basic techniques of ‘marking out’.

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SELF ASSESSMENT At the end of each section you, the student, are asked a series of YES and NO questions. If any question is unclear our you have answered NO, then you are encouraged to review the materials in that section again. SECTION THREE HISTORY OF MEASUREMENTS Do you know how the ancient Romans developed a measurement system, and why was this system not accurate? MEASURING TOOLS Can you describe what the following measuring tools are specifically designed for;

Venier Callipers? Micrometers? Steel Rules? Combination Sets?

FIXED GAUGES Are you able to explain what some of the types of standard fixed gauges are, and what they are used for? MARKING OUT TOOLS Do you remember what the following marking and tools are designed for;

Chalk Strings? Steel Rules? Flexi Curves? Scribers? Trammels? Ball Peen Hammers?

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CARE AND MAINTENANCE OF MEASUREMENT AND MARKING OUT TOOLS Can you recall the maintenance requirements for the following tools;

Surface or marking out tables? Callipers? Protractors? Tape Measures?

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STUDENT NOTES