Chapter 4 Producing components using hand fitting equipment © Pearson Education 2012 Printing and photocopying permitted Producing components using hand fitted equipment

Chapter 4 Producing components using hand fitting equipment © Pearson Education 2012 Printing and photocopying permitted Using tools ●Cables, extension leads and hoses should be checked for damage. ●Files must have a secure handle and checked for cracks and splits. ●Hammers should be checked for cracks and chips and the head should be secure on the handle. ●Chisels should not be used if the striking face has ‘mushroomed’. Tools should always be kept in the best possible condition: What could happen if these checks are not made to the tools?

Chapter 4 Producing components using hand fitting equipment © Pearson Education 2012 Printing and photocopying permitted Making a plan Before starting a plan you need to consider: ●Correct choice of datums to suit the work you are making. ●The work holding techniques you are going to use. ●The correct process of work in the right sequence. ●The quality checks you will need to make. ●Whether the tools and equipment you need are available.

Chapter 4 Producing components using hand fitting equipment © Pearson Education 2012 Printing and photocopying permitted Datums Datums are the workpiece reference points so must be correct as the work’s accuracy depends on them. The three types of datum are: ●Edge of face datum ̶ taken from a true edge, it allows accurate marking out using a surfaced table. ●Linear datum ̶ a line marked on a component (e.g. through the centre or in a convenient position for a range of features). ●Point datum – the simplest datum, taken from a single point (e.g. a hole or a mark), often used as castings where the hole position is the most important so must be central.

Chapter 4 Producing components using hand fitting equipment © Pearson Education 2012 Printing and photocopying permitted Hacksaws Designed to cut metal with adjustable frames to accept different blade sizes. Blades are made from three different materials: ●High carbon steel ̶ cheap blades used for softer materials. ●High speed steel ̶ very hard and brittle and can shatter if twisted while cutting. ●Bi metal blades ̶̶ expensive, high speed steel teeth welded into a carbon steel backing.

Chapter 4 Producing components using hand fitting equipment © Pearson Education 2012 Printing and photocopying permitted Using hacksaws ●Select the correct blade for the material being cut. ●Fit the blade to the frame, with teeth facing away from the handle. ●Tension the blade until it is taut. ●If right handed, stand facing the saw and hold the saw in your right hand. Use your left hand to hold the front of the saw and steer it and hold it straight. ●Concentrate on moving the saw forward and back in a controlled manner, at a steady pace and not pushing too hard. Make sure you use the full length of the blade.

Chapter 4 Producing components using hand fitting equipment © Pearson Education 2012 Printing and photocopying permitted Steps for good filing ●Step 1 ̶ Hold the workpiece tight in a bench vice at the correct height. Avoid too much metal sticking out as this can cause the vice to vibrate. ●Step 2 ̶ Stand almost sideways to the bench with your feet shoulder width apart. As you file the line you move in should be roughly in line with your right toes (if right handed). ●Step 3 ̶ Grip tight; if right handed grip the file tight in your right hand and support the front of the file with your left. The right hand is for power, the left for control. As you file move the weight from the front of the file to the back, to stop the file rocking.

Chapter 4 Producing components using hand fitting equipment © Pearson Education 2012 Printing and photocopying permitted Achieving a flat surface with filing This is known as cross filing. ●Clean the surface table with a light oil or rag. ●Lightly cover the surface with engineer’s blue. ●Rub the surface to be filed flat over the engineer’s blue. The high spots will be revealed. ●Select a flat file, place the workpiece in a vice and file at 45˚ to the front of the workpiece, focusing on the areas shown in engineer’s blue. ●Clean the workpiece and recheck with engineer’s blue. ●Continue until there is an even blue surface on the workpiece. Describe the process used for drawfiling and for filing external and internal curves.

Chapter 4 Producing components using hand fitting equipment © Pearson Education 2012 Printing and photocopying permitted Scraping Scrapers are used to make a more accurate surface than filing. They can also be used to produce a decorative face. Scrapers remove only a small amount of metal and should only be used on a surface that has been worked true. Types of scrapers include: ●Flat scraper ●Half-round scraper ●Triangular scraper

Chapter 4 Producing components using hand fitting equipment © Pearson Education 2012 Printing and photocopying permitted Chiselling Cold chisels are effective cutting tools and can be used for a variety of work. They are made from high carbon steel and hardened and tempered at the cutting edge. The end that is hit with a hammer is left soft to prevent it chipping.

Chapter 4 Producing components using hand fitting equipment © Pearson Education 2012 Printing and photocopying permitted Lapping Lapping produces a good surface finish or an accurate fit between two parts. An abrasive paste or slurry is used when lapping. The grit size of the abrasive is chosen to suit the required finish. ●Clean all traces of dirt and old abrasive from the lapping plate. ●Apply the appropriate abrasive paste evenly to the plate. ●Lay the workpiece on the lapping plate and with gentle pressure move the workpiece in a circular motion on the lapping plate, rotating the piece with your hand.

Chapter 4 Producing components using hand fitting equipment © Pearson Education 2012 Printing and photocopying permitted Drilling For hand fitting most drilling will use a bench drill or pillar drill. They have a table that can be raised or lowered. They have a range of different spindle speeds. Using the Internet, catalogues and Your workshop, find out about the different drills bits that can be used.

Chapter 4 Producing components using hand fitting equipment © Pearson Education 2012 Printing and photocopying permitted Cutting fluids and compounds There are three main types of these: Straight oils – vegetable, animal, synthetic or mineral oils. Usually clear and act mainly as a lubricant, they are expensive but are good for low speed operations. Soluble oils – these can be emulsified with water and are effective coolants that allow fast cutting speeds and are cost effective. They do make the work harder to see and are not such good lubricants as straight oils. Greases – soft and used for tapping, rearming and other cutting operations where friction needs to be reduced. Give a good surface finish and reduce tool wear but do not remove swarf in the same way as soluble oils.

Chapter 4 Producing components using hand fitting equipment © Pearson Education 2012 Printing and photocopying permitted Cutting screw threads Screw threads are used to fasten components together. They are self locking and can be opened and closed to help disassemble a component. You need to always use the correct tap or die for the thread required. Taps are made from high speed steel (HSS) or high carbon steel (HCS).

Chapter 4 Producing components using hand fitting equipment © Pearson Education 2012 Printing and photocopying permitted Taps Taps are available in sets of three: Taper tap – tapered for two thirds of its length and used to start the thread, the taper helping it to align with the hole and cut a new thread. Second cut (intermediate) tap – a taper for a third of its length and used after the taper tap to enlarge the thread to the correct size Plug (bottoming) tap – cut a parallel thread for their whole length but have a chamfered thread to help with cutting.

Chapter 4 Producing components using hand fitting equipment © Pearson Education 2012 Printing and photocopying permitted Cutting external threads External threads are cut by a die. They are made from the same materials as taps. The die has a split in it for adjusting depth of cut. To do this, screw the tapered ended centre screw into the die, spreading the die and making it a large diameter. The die should then be locked in place using the two locking screws. A thread is then cut and checked either with a thread gauge or a suitable nut. All three screws must be present in the die stock to prevent the die shifting.

Chapter 4 Producing components using hand fitting equipment © Pearson Education 2012 Printing and photocopying permitted Reaming Reamers are used when holes need to have an accurate size. A hole is drilled slightly undersize and then finished by reaming. Reaming is best done using a hand reamer to ensure accuracy. Turn the reamer slowly and smoothly avoiding excessive pressure. Workpiece must be properly supported and firmly held in position. The correct size tap wrench must be used. Never turn the reamer backwards even when removing the reamer.

Chapter 4 Producing components using hand fitting equipment © Pearson Education 2012 Printing and photocopying permitted Hand grinding machines This is used for sharpening cutting tools. It has a coarse wheel and a fine wheel. When using a grinder: Always stand to the side when you turn the machine on. Never use the side of the wheel to grind. Move the tool evenly over the wheel, using all the surface. Only grind for a short time then cool the workpiece.

Chapter 4 Producing components using hand fitting equipment © Pearson Education 2012 Printing and photocopying permitted Micrometers Micrometers are some of the most accurate measuring tools used. The spindle has a pitch of 0.50 mm. The thimble is graduated with 50 divisions around its circumference, meaning each of these divisions is 0.01 mm.

Chapter 4 Producing components using hand fitting equipment © Pearson Education 2012 Printing and photocopying permitted Measuring work: Vernier calipers These are versatile measuring instruments used to measure internal and external measurements and depths. A metric Vernier calliper has two scales: The main scale is on the body of the calliper and graduated in mms. The scale on the sliding jaw has 50 divisions and is numbered from 1-5 in every five divisions. Each division has a value of 0.02 mm.

Chapter 4 Producing components using hand fitting equipment © Pearson Education 2012 Printing and photocopying permitted Measuring work: Dial test indicators These are sensitive instruments, using a set of gears and a rack or pinion mechanism to compare measurements. A 1 mm move of the plunger will turn the dial hand one full circle. The face of the circle is graduated to 0.01 mm divisions so accurate comparisons can be made.