Marking Out, Measurement, Fitting & Assembly - The Hong Kong ...

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Marking Out, Measurement, Fitting & Assembly - The Hong Kong ...

Marking Out, Measurement, Fitting & AssemblyMarking Out,Measurement, Fitting &AssemblyObjectives:To understand the importance of hand processes in fitting & assemblywork.To identify and use common hand tools for measurement, marking out,and fitting purposes.To be familiar with the basic techniques involving some common handprocesses.1. IntroductionThis training module is designed to give you a good appreciation on the varioustypes of band tools commonly used for measurement, marking out, and metalremoval. Emphasis is not placed on you to become a skilful fitter within such ashort period of training, but rather to let you understand the uses of commonhand tools and appreciate the importance of fitting work in the trade.Nevertheless, on completion of the training and through the hands-on practicegiven, you will acquire some of the basic skills and techniques involved with thesehand processes.To get the maximum benefit from the training, it is essential that you use everyopportunity to consolidate what you observe and to interact between yourself andthe staff member in charge of your training. This is self-motivated and the desiremust come from you.Page 1IC Professional Training


Marking Out, Measurement, Fitting & Assembly2. Why Using Hand Tools?"Man without Tools is nothing; with tools he is all." - This sentence, which wasdefined by Thomas Carlyle, has well elaborated the importance of tooling to aman.The term 'Tooling' as applied to the engineering discipline refers to anyequipment or instruments that give helps in the production of a product or anyrelated activities. Simply speaking, it ranges from the most fundamental type ofhand tools, such as a File, to the very complex machine tools, such as a CNCMachining Centre.Thus, one may ask the question - Why we still have to use band tools in thismodern age of technologies?Yes, it is reasonable to say that the efficiency of any hand processes is low and thequality of outcome depends highly upon the skill of individuals. Perhaps it is fair toconsider the following points before a definite answer is given to the abovequestion: -2.1 AccuracyAlthough the CNC machine can give a higher degree of dimensional accuracywhen compared with the inconsistent outcome of hand fitting, the extreme highdegree of flatness required for a surface table or a machine slideway is usuallyobtained by hand scraping only.2.2 FlexibilityHand processes are very flexible and can be carried out at any place necessarilywhile machining processes cannot be. In addition, machining usually requires arigid setting up, while fitting is simple.2.3 QuantityFor large batch size, advanced production machines are commonly employed inorder to maintain the accuracy as well as the efficiency, but for "jobbing type"works, such as manufacturing of a prototype or repairing a single component, itwould be uneconomic to use these advanced machine tools. Instead, "jobbingtype" works are usually produced by conventional machining and followed byhand fitting necessarily.2.4 Final AssemblyIn the assembly of precise component parts, no matter how accurate they arebeing produced, a skilful fitter is often required to give the necessary "finishingtouch" on them to ensure that everything goes together correctly.Page 2IC Professional Training


3. Measuring Tools in Workshop3.1 CalipersMarking Out, Measurement, Fitting & AssemblyCalipers are the very simple tools used together with a steel rule for themeasurement or comparison of linear dimensions. An experienced worker canachieve +/-0.05mm in the measurement. Calipers are classified into two types:Outside CalipersOutside calipers, as shown in Fig. 1, are used for measuring external dimensionssuch as the length, diameter, or even the thickness of a solid.Fig. 1 Outside CalipersInside CalipersInside calipers, as shown in Fig. 2, are used for measuring internal dimensionssuch as the diameter of a hole, or the width of a slot, etc.Fig. 2 Inside CalipersPage 3IC Professional Training


Marking Out, Measurement, Fitting & Assembly3.2 Vernier CalipersVernier Calipers, as shown in Fig. 3, are the more precise tools that capable formeasuring external dimensions, internal dimensions, and depths. Besides, bothpairs of measuring jaws and the depth gauge have the main features thatincluding a main scale and a vernier scale.Fig. 3 Vernier CalipersThe resolution of a vernier scale is determined by the difference on the distanceof one division on the main scale and one division on the vernier as shown in Fig.4. For example, a vernier scale of length 49mm is divided into 50 equal divisions.That means ONE division on the vernier represents 49/50 = 0.98mm while ONEdivision on the main scale represents 1mm. Then, the resolution of the vernier is1mm - 0.98mm = 0.02mm.Fig. 4 Vernier ReadingPage 4IC Professional Training


4. Marking Out Tools in WorkshopMarking Out, Measurement, Fitting & AssemblyMarking out is the preliminary work of providing guidance lines and centresbefore cutting and machining. The lines are in 3-D and full-scale. The workpiececan then be cut or machined to the required shape and size. The common toolsused for marking out are as follow:4.1 ScriberA scriber, as shown in Fig. 13, is used for scratching lines onto the workpiece. It ismade of hardened tool steel, which is hardened and tempered to a suitablehardness.Fig. 13 Scriber4.2 Engineer's SquareEngineer's square, as shown in Fig. 14, is made of hardened tool steel. It is groundto a precise squareness and straightness. It is not only used for checking thestraightness and the squareness of a workpiece, but it can also be used formarking parallel or perpendicular lines onto a workpiece.Fig. 14 Engineer's Square4.3 Spring DividersSpring dividers, as shown in Fig. 15, are made of hardened tool steel. The legs areused for scribing arcs or circles onto a workpiece.Fig. 15 Spring DividersPage 8IC Professional Training


Marking Out, Measurement, Fitting & Assembly4.4 PunchThere are two types of punch named as the Centre Punch and the Dot Punch. Adot punch has a point angle of either 30 or 60 degrees, so it can be used formarking small dots on the reference line. The centre punch has a point angle of 90degrees as shown in Fig. 16. It is used for making a large indent on a workpiece fordrilling. Both punches are made of hardened tool steel.Fig. 16 Punch4.5 Surface PlateSurface plate, as shown in Fig. 17, is made of malleable cast iron. It has beenmachined and scraped to a high degree of flatness. The flat surface is being usedas a datum surface for marking out and measuring purposes. Large surface platethat can stand on the floor is known as surface table.Fig. 17 Surface PlatePage 9IC Professional Training


Marking Out, Measurement, Fitting & Assembly4.6 Angle PlateAn angle plate, as shown in Fig. 18, is used for supporting or setting up workvertically. Slots and holes are provided for mounting and fixing the workpiece. It ismade of cast iron and ground to a high degree of accuracy.Fig. 18 Angle PlateFig. 19 Vee Block4.7 Vee BlockVee blocks, as shown in Fig. 19, usually in a couple are made of cast iron or steelin case-hardening. They are generally used to hold circular workpiece for markingout or machining.Page 10IC Professional Training


Marking Out, Measurement, Fitting & Assembly5. Hand Tools for Workshop5.1 Bench ViceA bench vice, as shown in Fig. 20, is the device for holding the workpiece wheremost hand processes to be carried out. The body of the vice is made of cast ironwhile the two clamping jaws are made of hardened tool steel. Some bench vicehas a swivel base, which can set the workpiece at an angle to the table. The viceheight should be correct ergonomically. In order to protect the workpiece frombeing damaged by the jaws, vice clamps are employed. Vice clamps, which aremade of copper, are fitted over the vice jaws when holding finished work.Care of VicesFig. 20 Bench Vicea. Do not direct impact the vice body by the hammer.b. Light hammering can be done on and only on the anvil of the vice.c. To avoid over clamping, the handle of the vice should be tightened by handonly5.2 FilesFiles are the most important hand tools used for the removal of materials. Theyare made of hardened high carbon steel with a soft 'tang', which is used for fixinga handle. Files are categorised as follows:-Fig. 21 FilePage 11IC Professional Training


Length - measured from the shoulder to the tipShape - the cross-sectional profileGrade - the spacing and pitch of the teethCut - the patterns of cutting edgeSave EdgeMarking Out, Measurement, Fitting & AssemblyThere are no cutting edges on one side of the hand file. The purposes for the saveedge is to avoid the worker from damaging the work, when he is filing a shoulderposition.Shape of Files1. Hand File - The common file used for roughing and finishing. It is rectangular incross section and parallel in width. It has double cut teeth on both faces, single cutteeth on one edge, and one save edge.Fig. 22a Hand File2. Flat File - It is similar to a hand file, which is rectangular in cross sectionand tapered slightly in width that towards the tip. It has double cut teeth onboth faces and single cut teeth on both edges.Fig. 22b Flat File3. Half-round File – The cross section is a chord of circle with its taper towardsthe tip. It is used for forming radii, grooves, etc. Its flat side is used for finishing flatsurfaces.Fig. 22c Half-round File4. Round File - This is a round shaped cross section file with tapering toward theend. It is used for enlarging holes and producing internal round corners. It usuallyhas double cut teeth in the larger sizes, and single cut teeth for the smaller sizes.Fig. 22d Round FilePage 12IC Professional Training


Marking Out, Measurement, Fitting & Assembly5. Square File - This is a file with square in section and taper towards the tip. Itusually has double cut teeth on all four faces. It is used for filing rectangular slotsor grooves.Fig. 22e Square File6. Three Square File - It is also known as triangular file. It is triangular in crosssection with taper towards the tip. It has double cut teeth on both faces. It is usedfor filing corners or angles less than 90°.Fig 22f Three Square File7. Needle Files - Needle files are a set of small files with their shapes made in away similar to the large ones. They are generally used for small and delicate works,such as the repair of small instruments.Cut PatternSingle Cut - There is only one set of cutting teeth on the surface. It gives a lessefficient cutting but a better finish. It is suitable for filing soft metal.Double Cut - A double cut file has two sets of teeth, one at 70 degrees to the edgeand the other one at 45 degrees to another edge. Thus, it is more efficient incutting. It is easy to clog the teeth when it is used to file the soft metal.Rasp – These are very coarse teeth, like the nail. This type of teeth commonly usedfor cutting off soft materials, such as rubber, PVC, and wood, etc.GradeIt refers to the pitch (spacing) of the teeth that spread throughout the wholelength of the file. Files with a rougher grade of cut give a faster metal removal ratebut a poorer surface finish or the vice versa. It should be noted that, for the samegrade of cut, a longer file would have a coarser pitch than a shorter one. There arefive grades of cut, which are Rough, Bastard, Second, Smooth, and Dead Smooth.The following three grades of cut are used commonly.Bastard cut - medium teeth for general purposes, especially suitable for mild steel.Second cut - finer teeth for cutting hard metals.Smooth cut - fine teeth for finishing.Page 13IC Professional Training


Marking Out, Measurement, Fitting & AssemblyFiling is a hand process of using appropriate files to produce required shape, sizeand quality of surfaces or components.A lot of practice is required before you can master the techniques and skills.Nevertheless, through the hands-on practice given to you, you will have theopportunity to appreciate the various filing methods.Safety and Care of Files1. File teeth are brittle and therefore file should be placed properly and shouldnot be stacked on other tools.2. New files should never be used on hard materials, e.g. casting or welding joint.3. Some brittle metal, e.g. brass, is not readily filed with the worn teeth.4. The pinning file should be cleaned regularly with file card / wire brush.5. Files should be use in cutting on the forward stroke.6. Files without handle should not be used.5.3 File CardWhen filing the soft metals, the small pieces of metal will tend to clog the teeth. Ifthe file is not cleaned, the small pieces of metal will scratch on the surface of thework. It is called pinning. This case is frequently appeared when applying a newsmooth file on the soft metals. The pinning can be removed with a file card asshown in Fig. 23, which is a wire brush mounted on a block of wood. Sweep thefile card along the grooves on the file until the pinning is removed.Fig. 23 File Card5.4 HacksawA hacksaw is generally used for cutting a metal into pieces. It consists of a frameand a saw blade as shown below. It is a "U" shaped steel frame with a pistolhandgrip and a saw blade as shown in Fig. 24. The frame, which is used for holdingthe blade firmly in position, is usually made of mild steel. The fixed type of framecan only take one length of blade, whereas the adjustable type can take differentblade lengths. It has a wing nut to adjust the tension of the blade.Page 14IC Professional Training


Marking Out, Measurement, Fitting & AssemblyFig. 24 HacksawSaw BladeSaw blades are made of high carbon steel, alloy steel or high speed steel. They aresupplied according to material, hardening, length and pitch.1. Hardening – The saw blade is usually supplied with all-hard or flexible grade.The all-hard is very brittle, and it is suitable for the skilful user only. The flexiblegrade is tough, so it can twist an angle. It is suitable for cutting a curve or for thebeginner to use.2. Material – Usually, the saw blade is supplied with high carbon steel (HCS) andhigh speed steel (HSS). The HCS will be annealed from the heat generated byfraction of cutting. The HCS saw blade will lost its hardness when cutting the hardmetal. The HSS can keep its hardness unless improper use.3. Pitch - It is classified according to thenumber of teeth per 25mm.Coarse blade (18T) is most suitable for softmaterial and thick workpiece.Medium blade (24T) is suitable for steel pipe.Fine blade (32T) is suitable for the thin metalsheet and thin copper pipe.For safety, it is advised that to keep at least 3teeth of the blade, stand on the workpiece.Fig. 25 Pitches of Saw Blade4. Length - The length of the blade is determined by the distance between theoutside edges of the holes, which fit over the pegs.5. Set - The teeth have a "set" to either side alternately, which causes the blade tocut a slit wider than the thickness of the blade, to prevent jamming.Safety and Care of Hacksaw1. The cutting action is carried on the forward action only. So the blade must bemounted with its teeth pointing forward.2. Suitable tension should be applied on the blade to avoid breakage or loosen.3. Change the blade if some teeth are broken.4. Avoid rapid and erratic strokes of cut.Page 15IC Professional Training


Marking Out, Measurement, Fitting & Assembly5. Avoid too much pressure.6. Workpiece must be hold firmly.5.5 HammerThe type most commonly used is the ball pein hammer, which has a flat strikingface and a ball-shaped end (call the pein). Hammer heads are made from mediumcarbon steel. The two ends must be hardened and tempered, the centre of thehead with the eye is being left soft. It is specified according to its weight.Fig. 26 HammerSafety and Care of Hammer1. The hammer head is firmly fixed to the shaft by a wedge.2. The striking face of the hammer head does not wear.Page 16IC Professional Training


Marking Out, Measurement, Fitting & Assembly6. Drill and DrillingDrilling is the process of cutting holes in metals by using a drilling machine asshown in Fig. 27. Drills are the tools used to cut away fine shavings of material asthe drill advances in a rotational motion through the material.Fig. 27 Drilling Machine6.1 Twist DrillThe twist drill, as shown in Fig. 28, is made of high speed steel. It is tempered togive maximum hardness throughout the parallel cutting portion. Flutes areincorporated to carry away the chips of metal and the outside surface is relievedto produce a cutting edge along the leading side of each flute.Fig. 28 Twist DrillsPage 17IC Professional Training


Marking Out, Measurement, Fitting & Assembly6.2 Drill FeaturesThe point of the drill is ground to anangle of 59 degrees to the centre line togive two equal cutting edges, and eachside is ground back to give "relief" ofabout 12 degrees to each cutting edge asshown in Fig. 29.It is very important that drill points arecentral, the lip angles are equal, Thecutting edges are unchipped, and theclearance angle is correct. To obtain thisstate and ensure correct angles, it isimportant that drills are ground in agrinding machine.Fig. 29 Drill Features6.3 Drill Operating ParametersIt is essential to select the correct cutting speed and feed. The following tableshows the most common used cutting speed and feed rate.Cutting SpeedMaterialMild steelStainless SteelAluminiumCutting Speed6 - 9 m/min4 - 9 m/min30 - 36 m/minFeed Rate5.5 mm diameter twist drill 0.08 - 0.15 mm/rev30 mm diameter twist drill 0.04 - 0.55 mm/revPage 18IC Professional Training


Marking Out, Measurement, Fitting & Assembly6.4 Special Type of DrillCounterbore Drill, as shown in Fig. 30, is used to form a flat, or cylindrical recessto accommodate the head of the bolt. It is also used to provide a level base on therough surfaces for nuts and washers.Fig. 30 Counterbore DrillFig. 31 Countersink DrillCountersink Drill, as shown in Fig. 31, is used to form a conical shaped recess toenable a countersunk screw or bolt to fit flush with the surface of the work.6.5 Safety and Care on Drillingi. Twist drill must be clamped in the drill chuck tightlyii.iii.iv.The workpiece to be drilled must be firmly secured by vice, or clamps.Drill guard, as shown in Fig. 32, must be closed before switch on themachine.Use the correct drilling speed and apply suitable drilling force It isadvisable to release the drill occasionally, lift the drill, and clear the hole ofcutting.v. Apply cutting fluid in the cutting except for drilling Cast iron.vi.vii.Take care, when the drill is nearly penetrated through the workpiece.The "screw in" action can lift up the workpiece.Fig. 32 Drill GuardPage 19IC Professional Training


4. Safety, Precautions & Operation in Reaminga. Care the sharp cutting edge especially in handling.Marking Out, Measurement, Fitting & Assemblyb. The amount of material to be removed by a reamer should be as small aspossible, approximately 2-4% of diameter.c. Reamer must only be turned in one direction, both cutting and removing thetools, otherwise the tool may jam.d. Lubricant oil should be used except when cutting cast iron and brass.e. Reaming can enlarge the size of hole, but cannot correct the position error indrilling.7.2 TapTaps, as shown in Fig. 36, are used to cut the internal screw threads. Taps aremade of hardened High Carbon Steel or High Speed Steel. The ends of the shankare square to fit a wrench, as shown in Fig. 37. Usually taps are provided in set ofthree - taper, second and plug tap.Fig. 36 Taps1. Taper TapThe tap is tapered off for a length of 8 to 10 threads and is the first tap to beused in a hole to start the thread form.2. Second TapThe tap is tapered off for a length of 4 to 5 threads to facilitate picking up thethreads cut by the taper tap.3. Plug TapThis is fully threaded throughout its length and is called a 'bottoming' tap. Thistap used to cut the bottom of a blind hole.Fig. 37 Tap WrenchPage 21IC Professional Training

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