Screwdrivers PDF

Screwdrivers The Screwdriver Screwdrivers are intended to be used to tighten or loosen screws and should not be used for other purposes. Screwdrivers are divided into three main groups: those suitable for slotted screw heads, those for recessed screw heads and automatic types. 2023-11-24 B-07b Maint...

Screwdrivers The Screwdriver Screwdrivers are intended to be used to tighten or loosen screws and should not be used for other purposes. Screwdrivers are divided into three main groups: those suitable for slotted screw heads, those for recessed screw heads and automatic types. 2023-11-24 B-07b Maintenance Practices CASA Part 66 - Training Materials Only Page 142 of 498 Slotted Screw Heads Slotted screwdrivers are the most familiar and generally used type and consist simply of the handle, shank and blade. The handle of the screwdriver is usually constructed of fluted wood or plastic material and a high-carbon or alloy steel shank/blade, with the tip of the blade ground to fit the slot in the head of the screw. They are classified by the length of the shank and the width of the blade. Some large screwdrivers have a square section shank, while smaller ones may have a square or hexagonal portion where the shank enters the handle. A spanner may be used on this to apply extra torque when loosening screws. It should not, however, be used for tightening. A large, long-shanked screwdriver is often referred to as a GS (general screwdriver) and may be useful as a lever for releasing catches an opening cowlings, but most screwdrivers should be used only for driving screws. They should not be used as chisels, punches, drifts or pry bars. Stubby and off-set screwdrivers are used in areas of restricted access. Screwdrivers - slotted 2023-11-24 B-07b Maintenance Practices CASA Part 66 - Training Materials Only Page 143 of 498 Recessed Screw Heads It has become common practice to employ fasteners with complex recessed drive slots to reduce the tendency of the tool to slip and permit greater torque application to the fastener. The shape of the recess requires the use of a specific shape and size of screwdriver tip. For example, the cruciform Phillips, the less common American Reed & Prince and the European Pozidriv all look very similar, but use of the wrong driver will damage the slot and prevent removal of the fastener. The tri-wing slot has 15 sizes to cover the complete range of fastener sizes. Phillips screwdrivers So that the engineer does not need to carry a wide range of screwdriver sizes and styles, screwdriver bits are produced. Smaller sizes are normally hexagonal in cross section and fit into a special screwdriver or bit holder socket, in which they are retained by a spring device or magnetic insert. The bit holder socket can be used with a wide range of tools, including ratchet handle and extension, speed brace and torque wrench. Standard sockets should not be used as the lack of retention device will enable the bit to fall into the component or structure. Larger bits have a square drive recess and can be fitted directly onto any socket drive tool. Some bits are made with an anti-cam out feature, comprised of serrations on the 'undo' faces to prevent the tool lifting out when torque is applied to remove the fastener. 2023-11-24 B-07b Maintenance Practices CASA Part 66 - Training Materials Only Page 144 of 498 Screwdriver bits Ratchet Screwdrivers The ratchet type screwdriver consists of the handle, the ratchet mechanism and the blade. Sometimes the blade is removable so that various sizes and types of blades may be used. The ratchet mechanism is designed to operate in clockwise rotation, in anti-clockwise rotation or in a locked position so that the unit may be used as a standard screwdriver. The ratchet action permits rapid screw rotation in either selected direction for certain types of work. Screwdriver - ratchet 2023-11-24 B-07b Maintenance Practices CASA Part 66 - Training Materials Only Page 145 of 498 Pump Action Screwdrivers The pump action Yankee screwdriver is a reversible automatic driver which takes a variety of bits. Pushing the handle in spins the bit in the selected direction. Due to the danger of the bit slipping out of the slot during pumping and the potential for damage to the skin, Yankee screwdrivers are not recommended for aircraft use. Pump action screwdriver Offset Screwdriver The offset screwdriver is handy when there is not sufficient space to work using a conventional screwdriver. One blade is forged in line with the handle, and the other at right angles to the first blade. With such an arrangement, when swinging space for the screwdriver is limited, you can change ends after each swing. These screwdrivers are available in a range of screw sizes and tips, i.e. Phillips, Frearson and Pozidriv. Offset screwdriver Use and Selection of Screwdrivers 2023-11-24 B-07b Maintenance Practices CASA Part 66 - Training Materials Only Page 146 of 498 The ideal type and size of screwdriver depend on the head style of the fastener. The number of screws to be moved may indicate the choice of simple or mechanical operation (i.e. use of ratchet type). The size of screw indicates the torque requirement and hence the size of the screwdriver. Care must be taken when using screwdriver bits as excessive torque can be applied with socket drive and powered tooling. The tip of the screwdriver should be a good fit in the slot of the screw and not modified to fit. The width of a flat screwdriver blade should be the same diameter as the head of the screw. Straight-blade screwdriver tips should be at least 75% of the screw slot width. Philips and special screwdriver tips must fit the screw exactly. Undersized drivers suffer tip damage and also damage the slot of the screw head. For loosening tight or corroded screws, some screwdrivers have a square or hexagonal section shank to permit extra leverage to be applied. When turning a screw, do not the hold work in your hand. A slip of the blade can cause a painful injury. A damaged, bent or worn screwdriver should never be used. The screwdriver is designed for one principal purpose: to loosen or tighten screws. To successfully accomplish this purpose, the correct size must be selected for the job involved and excess torque must not be applied. Screwdrivers are probably the most commonly abused tool. They readily tempt people to use them as levers or chisels. These malpractices render a screwdriver unfit for its designed purpose and can result in personal injury and expensive damage to equipment. 2023-11-24 B-07b Maintenance Practices CASA Part 66 - Training Materials Only Page 147 of 498 Screwdriver selection Tri-Wing Some airlines use screws with a special screw head produced by the Phillips Screw Company. These screws have three slots instead of the four found on the regular cross-point screw. The screw head and bit are identified by the registered trade name Tri-Wing. Tri-Wing screwdriver head 2023-11-24 B-07b Maintenance Practices CASA Part 66 - Training Materials Only Page 148 of 498 Pozidriv A Pozidriv bit resembles the Phillips bit in that it has a cross shape. However, a significant difference in the bottom of the recess allows the bit to interlock with the screw head. This design is produced by the Phillips Screw Company and provides a tighter and more positive connection between the screwdriver tip and the recess in the screw. Posidriv screwdriver head Torx The Torx screwdriver is used to remove and install Torx-type screws, which have a six-pointed slot. It should not be used for an Allen type screw. Using the wrong type of screwdriver can damage both the screw and the screwdriver. Torx screwdriver head 2023-11-24 B-07b Maintenance Practices CASA Part 66 - Training Materials Only Page 149 of 498 Jewellers’ Screwdrivers Jewellers, instrument makers, toolmakers and others’ screwdrivers are especially adaptable for fine, delicate work. They are fitted with swivel knobs that are concave to fit the finger and are hexagonal in shape to prevent rolling. Screwdrivers are available individually or in sets. Blades vary in width from 0.025–0.100 in. (0.6–2.5 mm). There is also a blade available for No. 0 and No. 1 Phillips head screws. Overall length of screwdrivers is approximately 4 in. (100 mm). Screwdrivers - jewellers Other Screw Bit Types A wide selection of other specialist screwdrivers have been made to allow certain tasks to be accomplished. These can include: Offset (or cranked) screwdrivers – can reach screws with little clearance above their heads and may also have a blade at one end and a cross-point at the other Reversible tip screwdrivers – with hexagonal shanks, allow the shank of the screwdriver to be reversed in the handle to provide a different tip, with a blade at one end and a cross-point at the other end of the hexagonal shank Interchangeable tip screwdrivers – have a selection of socket-like tips that can be interchanged to suit any particular type of screw head. 2023-11-24 B-07b Maintenance Practices CASA Part 66 - Training Materials Only Page 150 of 498 Spanners The Spanner Spanners are widely used for tightening or loosening a wide range of threaded fasteners. They are: Used for turning threaded fasteners such as bolts and nuts Made with jaw openings to fit square or hexagonal nuts, bolts and screw heads Made of high tensile or alloy steel drop Forged and heat treated for strength Given a smooth surface finish for ease of gripping. The most common spanners are those which are used on the standard hexagonal heads of bolts, nuts, screws and similarly shaped fastening devices. Other spanners are often referred to as special or non-standard spanners and are used on different types of screw thread fastenings. Some of these special spanners have a limited application, while others are specifically produced for a particular component and are found only in special tool kits applicable to that component. Most spanners are manufactured from case-hardened mild steel, hardened and tempered highcarbon steel, or alloy steel, though some are made from copper alloys, where spark-resistant tools are required. The size of a spanner is marked either on the jaw face or on the shank, in the units of the type of thread system being used on the fastening device. The units shown on a particular spanner, however, relate to different parts of the fastening devices, so knowledge of the spanner sizing systems is necessary. The two main sizing systems are the: British Standard Institution (BS) and British Association (BA) Imperial system American/Unified (Imperial) and the metric system. The British Standard system uses Imperial units (fractions of an inch, etc.) and embraces two of the three main thread systems used in British engineering, one of which is no longer used in aircraft engineering. The sizing on BS spanners relates to the nominal diameter of the nut, bolt or stud on which the spanner is to be used. For example, a spanner marked 1/2 BS indicates that the spanner is used on a 1/2-in. diameter fastener, although the actual distance across the jaws of this spanner is 0.820 in. 2023-11-24 B-07b Maintenance Practices CASA Part 66 - Training Materials Only Page 151 of 498 Earlier BS spanners can be found with two figures stamped adjacent to each other (e.g. 7/16 BSW 1/2 BSF). The BSW figure relates to the Whitworth thread system, which is not used on aircraft due to its tendency to loosen when subjected to vibration. The BSF refers to the British Standard Fine thread, but to avoid confusion, the older system has now been brought into line with the BS system so that a 1/2-in. BS (BSF) spanner can, for general engineering purposes, also be used on a 1/2-in. Whitworth bolt/nut combination. British Association (the third British thread system) sizes also use Imperial measurements, and although they are in decimal fractions of an inch, they are represented by a whole number (2BA, 4BA, 6BA and so on) which again relates to the nominal diameter of the fastening device. The American Fine and Unified thread systems also use Imperial measurements. The sizes stamped on spanners refer to the dimensions across the spanner jaws (or across the flats of the hexagon of the fastening device). A spanner marked 1/2" A/F would be used on a bolt with an actual diameter of 5/16 in. Metric spanners are marked with a number also denoting the width (millimetres), across the flats, of the hexagon-shaped fasteners on which they are used. Spanner sizing systems The correct procedure must be followed to avoid using incorrect tools to install or remove a nut, bolt, stud or other fastening device. In some instances, the correct tool size may be quoted in the maintenance manual. This must be strictly followed. 2023-11-24 B-07b Maintenance Practices CASA Part 66 - Training Materials Only Page 152 of 498 Spanner Sizing Systems British Threads Spanners are marked with a number or fraction relating to the major diameter of the thread and the thread system, e.g. 1/4 BSW, 1/2 BSF, 2 BA, etc. Unified Threads The identification markings on spanners used for Unified thread hexagonal (and bi-hexagonal) headed fasteners refer to the measurement Across the Flats (A/F) of the hexagon. This dimension is expressed in fractions of an inch. The fractional sizes used are multiples of 1/2", 1/4", 1/8", 1/16", and 1/32" as applicable. The lowest possible denomination of a fraction is used. For example, a spanner intended for use with a bolt which is 0.25" across the flats would be marked 1/4" (not 2/8"). Metric Threads Spanners designed for use with metric threaded nuts and bolts are marked with the distance across the flats of the hexagon heads in millimetres. AF sizing for Hex and Bi-hex heads 2023-11-24 B-07b Maintenance Practices CASA Part 66 - Training Materials Only Page 153 of 498 Types of Spanners Open-Ended or Open Jaw Spanners The open jaw type of standard spanner is usually made in double-ended form to give two available sizes in one tool. Each open end of the spanner is of a different size, i.e. 1/4– 5/16 in., 0–2 BA or 6–7 mm. The head and jaw openings are usually at an angle of 15° to the shank. This is for use in confined spaces, where spanner movement is restricted. It enables a new grip to be made on the nut or bolt head by turning the spanner over. When using an open-ended spanner, it is necessary to ensure the spanner fits the nut or bolt head and that it sits squarely on the sides of the hexagon head. Whenever possible, pull the spanner rather than push. If the work requires the spanner to be pushed, use an open palm to avoid badly bruising the knuckles. The smaller the size of the spanner, the shorter its overall length. With a given amount of pull, a short spanner produces less twisting force than a larger one. This helps reduce the possibility of applying too great a force to the bolt, which would strip the threads or even shear the bolt or screw and is a design feature of spanners manufactured to a British Standard. The advantage of using this type of spanner is it may be fitted to the nut or bolt from the side and does not have to be placed over the nut or bolt head. One disadvantage of this type of spanner is the jaws of the spanner bear against only two of the six flats of the hexagon head or nut, so there is a definite tendency for the jaws to open when pressure is applied on the other end (especially in cheaper, low quality ones). Use of open jaw spanners is not recommended if one of the enclosed types can be used. Open-ended spanners 2023-11-24 B-07b Maintenance Practices CASA Part 66 - Training Materials Only Page 154 of 498 Ring Spanner These spanners give full enclosure of the hexagon head or nut, each corner of which engages snugly with an angle in the aperture of the spanner. The aperture is usually bi-hexagonal to facilitate use of the spanner when angular movement is restricted, but applies the load equally on all faces of the nut or bolt head. It can also be used on bi-hexagonal bolt heads and nuts. This type of spanner, like the open-ended type, is usually supplied in double-ended form to fit nuts or bolt heads of consecutive sizes, and it should be preferred over open jaw spanners if possible. The ends are generally cranked, but flat versions are also available. A ring spanner with very thin walls and a small crank is often referred to as a flange spanner. Ring spanners Ring/Open-Ended (Combination) Spanner The disadvantage of a ring spanner is the limitation of always having to lift and reposition it in order to continue loosening a fastener. On the other hand, an open-ended spanner is much easier to slip off and onto a nut. The ring/open-ended spanner combines a bi-hexagonal end and open end. The size of the hexagonal head nut or bolt the ends fit is the same. The open jaw end can be inclined to the shank, and the ring can be off-set or flat. Combination spanner 2023-11-24 B-07b Maintenance Practices CASA Part 66 - Training Materials Only Page 155 of 498 Flare Nut Spanner Flare nut spanners are designed with a gap in each ring to permit the spanner to be introduced to the hexagon where access is restricted, such as on union nuts in a pipeline installation, but still give a better grip than an open-ended spanner. The hex of the nut can be engaged every 15° of handle movement, which makes it ideal for confined spaces. Flare nut spanner Box Spanner Box type spanners give full enclosure of the nut or bolt head. They are particularly useful where access to the nut or bolt head is restricted to the line of the screw axis. Box spanners are used in conjunction with a tommy bar. As with the open jaw spanner, the box spanner must fit snugly on the nut. Box spanner 2023-11-24 B-07b Maintenance Practices CASA Part 66 - Training Materials Only Page 156 of 498 Ratchet Ring Spanner Ratchet ring spanners have a bi-hexagonal drive socket with a ratchet mechanism which permits the rapid run-down or loosening of nuts or bolts without the need to remove the spanner after each stroke. They usually have a different size drive at each end and may or may not be cranked. Some versions have a switch at the side of each head to reverse the ratchet direction, while others must be turned over to change from right-hand to left-hand drive. Note: With this type, it is possible to tighten a fastener and trap the spanner as its drive cannot be reversed. Ratchet ring spanner Open-Ended Ratchet Spanner The open-ended ratchet spanner has a modified jaw design which allows it to grip when turned in one direction, but slip (ratchet) in the other. This allows rapid run-down or loosening in areas with restricted access, but it should not be used to apply the final tightness or 'crack' tight fasteners. Open-ended ratchet spanner 2023-11-24 B-07b Maintenance Practices CASA Part 66 - Training Materials Only Page 157 of 498 Socket Spanners and Drive Accessories Socket spanners or, more usually, sockets, are used in conjunction with a variety of handles, extension pieces and universal joints. They can also be used with power tools, such as nut runners. The socket aperture is usually bi-hexagonal at one end to take the nut or bolt head, and square or hexagonal at the other end to accommodate the drive of the accessory. Common drive sizes are 1/4 in. and 3/8 in. square, while larger drives are used for larger sockets. Step-up and step-down adaptors are available to allow sockets to be used with different drives, but care must be taken not to overload the fastener or socket. A spring-loaded ball set in one face of the drive locates in a groove in the socket's drive aperture to retain the socket. Some larger sockets have a button to depress the ball and release the socket. Sockets are supplied in complete sets to cover a range of consecutive sizes. They may be produced in bright chrome, industrial (dull chrome or black) and impact grades, the latter being used with hightorque machine drivers and impact tools. Most sizes are available in deep, semi-deep and universal or 'wobbly' versions. Standard Sockets Standard sockets are available in all of the popular drive sizes and with either four-, six-, eight-, or 12point openings. These sockets are also deep enough to fit over a bolt head or a nut if too much shank does not protrude. The six- and 12-point sockets are used in aviation, whereas the four- and eightpoint sockets are available to turn square-head pipe plugs. Standard socket 2023-11-24 B-07b Maintenance Practices CASA Part 66 - Training Materials Only Page 158 of 498 Deep Sockets In several applications, a bolt extends through a nut too far for a standard socket to grip the nut. In these cases, deep sockets are available to allow the socket to grip the nut and still leave room for the bolt end. Deep sockets Flex Sockets When additional clearance is needed between the socket drive and the socket, a flex socket is used. Flex sockets have a pivot point between the drive handle end of the socket and the nut end. These sockets are made with both six- and 12-point openings and are available in the drive sizes most used in aviation maintenance. Flex sockets 2023-11-24 B-07b Maintenance Practices CASA Part 66 - Training Materials Only Page 159 of 498 Crowfoot Sockets Nuts are sometimes placed in locations on aircraft where a box-end, open-end, or standard socket wrench cannot be used. The crowfoot socket is designed to reach these nuts and is available with open, box and flare-nut ends. Furthermore, crowfoot sockets are available in several drive sizes, including 1/4 and 3/8 in. © Jeppesen Crowfoot socket 2023-11-24 B-07b Maintenance Practices CASA Part 66 - Training Materials Only Page 160 of 498 Handles and Adapters Extension Drives Extension drives are available in a variety of lengths for each drive size. Some have a knurled section to aid spin-down. Some have a modified drive square or wobble drive which allows some misalignment of the socket. Flexible drives composed of twisted steel wire strands are also available, but cannot be used where large amounts of torque must be applied. Extension drives Tee Bar Tee bars offer a simple method of turning a socket. Knuckle or breaker bars allow more force to be applied, which is very useful for cracking tight fasteners. Ratchet handles permit the fast run-down of fasteners, but should not be used to apply large torque loads. A speed brace enables very fast rundowns and is particularly useful when screwing down panels. Impact drivers contain a spring-loaded cam mechanism, and when struck with a hammer, a very high torque is applied to the square drive for cracking tight fasteners. 2023-11-24 B-07b Maintenance Practices CASA Part 66 - Training Materials Only Page 161 of 498 Speed Brace Time is an expensive commodity in aviation main­tenance, and therefore any tool that decreases the time required for all inspection or repair is typically used. One tool that can save a great deal of time is the speed brace. A speed brace resembles a bow ­type brace and has a socket or screwdriver bit snapped onto its end. Screws or nuts are turned much faster with a speed handle than they are with a conventional screwdriver or ratchet wrench. Socket handles and ratchets 2023-11-24 B-07b Maintenance Practices CASA Part 66 - Training Materials Only Page 162 of 498 Other Common Hand Tools Crowfoot Spanner Crowfoot spanners are employed where access by the previously mentioned spanners is not possible. They consist of a very short spanner with an open end, ring or split ring at one end and a square drive aperture at the other. They can be driven by an extension and one of the conventional socket drive tools, or by a cranked tee-bar as shown. The split-ring version is often referred to as an obstruction wrench. Crowfoot spanners C-Spanner and Adjustable C-Spanner The C-spanner is for use on slotted circular nuts and collars and is available in set sizes or a range of adjustable sizes. C-spanner and adjustable C-spanner 2023-11-24 B-07b Maintenance Practices CASA Part 66 - Training Materials Only Page 163 of 498 Peg Spanners Peg spanners are available in a variety of styles and are usually designed for specific applications. Peg spanners Strap Wrench A strap wrench has innumerable uses and will be found invaluable for removing round or irregularly shaped units. The strap is made for material such as plaited strand or oil-impregnated nylon and does not damage polished parts. Strap wrench 2023-11-24 B-07b Maintenance Practices CASA Part 66 - Training Materials Only Page 164 of 498 Allen Key Certain screws and bolts have a hexagonal recess in their head. The tool used for tightening or slackening these fasteners is the Allen key. It is made of hexagonal section tool steel bar and is cranked at 90° to give leverage. These spanners come in sets, with a typical set consisting of eight spanners ranging from 1/16 to 1/4 in. across the flats of the hexagon. Hexagonal screw drivers are also available. Both keys and screwdrivers are sometimes supplied with a ball end which allows a degree of indirect driving. Allen key Spanner Selection Ring or socket spanners are to be used wherever possible in preference to open-ended spanners since the latter tend to spread and slip. The final choice of spanner type depends on: Type of bolt or nut head form Accessibility Degree of tightness Quantity of same type and size bolts or nuts to be moved. Adjustable spanners and wrenches should not be used on aircraft components, but may be used to adjust tooling and ground equipment. The size of the bolt, nut or union dictates the size of spanners, which must fit snugly and with full engagement. (Damage to equipment or injury to operator can be caused by using spanners of the incorrect type or size, or those which are worn.) Never shim the jaws of a worn or oversized spanner to fit the nut. In the absence of torque loading instructions, excessive loading either by undue applied force or by application of additional leverage must not be used. 2023-11-24 B-07b Maintenance Practices CASA Part 66 - Training Materials Only Page 165 of 498 Normally: Bolt heads should be held firm with one spanner while its nut is moved by another. A union adapter should be held firm with one spanner while its union nut is moved by another. When screwing a fastener into a threaded hole or anchor nut, it is necessary to turn the fastener, but in all other cases the nut should be turned. Pipe unions must always be tightened with two spanners: one to prevent rotation of the union, while the other is used to move the union nut. Care must be taken not to over-torque when using the smaller sizes of sockets since the turning handles are sized to drive the largest socket in the set. When using any spanner: Ensure your footing is sound and you are protected from falling. Spanners and hands must be free from oil or grease to reduce slipping hazards. Whenever possible, apply force by pulling the spanner towards you. If pushing is unavoidable, push with the palm and keep the hand open to protect the knuckles in the event of slippage. When loosening pipe unions, ensure the system is depressurised and wear eye protection in case of residual pressure in the line. 2023-11-24 B-07b Maintenance Practices CASA Part 66 - Training Materials Only Page 166 of 498 Broken Tap, Bolt and Stud Removal Broken Taps It is often necessary to extract or remove a stud, tap or tool that is broken through carelessness or incorrect use. There are several ways to perform this operation. Extreme caution must always be exercised when the following processes are used. Broken taps present a considerable amount of difficulty for the following reasons: They are manufactured from high-speed steel. The remaining broken portion is generally stuck hard. Two methods can be used to remove broken taps: the punch method and a metal disintegrator. The success of these methods depends on the type of material being tapped and the experience of the operator. Punch Method Sometimes it is possible to screw the remaining piece of tap out of the hole by lightly tapping the broken piece with a hammer and punch as illustrated below. If space permits, it is even better to use two punches at opposite sides, 180° apart. This, however, requires two people working together. Refer to the illustration: Punch method 2023-11-24 B-07b Maintenance Practices CASA Part 66 - Training Materials Only Page 167 of 498 Metal Disintegrator If available, the metal disintegrator is the most effective method of all. However, there are limitations on where it can be used and on the size of components. The illustration shows a metal disintegrator. This machine uses a hollow electrode that burns its way through the centre of the tap while water flows through the hollow electrode to keep it cool. Electrodes are available in various sizes to suit different size taps. Metal disintegrator Broken Bolts and Studs Removing a broken bolt or stud does not present the same problems as does the removal of broken taps. This is because bolts and studs are not generally hardened, allowing them to be removed with the aid of a screw extractor. 2023-11-24 B-07b Maintenance Practices CASA Part 66 - Training Materials Only Page 168 of 498 Screw Extractors Screw extractors are available in two types: tapered, and straight or parallel. Tapered Screw Extractor The tapered screw extractor is a hardened steel tool that is tapered and has left-handed spiral flutes (see the illustration). When this tool is inserted into a previously drilled hole in the stud and turned anti-clockwise by a suitable tap wrench, the extractor wedges itself tightly into the hole and the broken bolt or stud should screw out. It is important to note that excessive force should not be applied to the extractor. If you apply excessive force and the extractor breaks, you will be confronted with a bigger disaster than the broken bolt, as the extractor is made of carbon steel and cannot be drilled. Taper screw extractors are available in a range of sizes to suit various size studs and bolts. The size of the extractor is determined by numbers and not dimensions, as with bolts. The size of the hole to be drilled in the stud is generally inscribed on the shank below the size of the extractor. Tapered screw extractor 2023-11-24 B-07b Maintenance Practices CASA Part 66 - Training Materials Only Page 169 of 498 Straight Screw Extractor The straight screw extractor consists of a hardened steel rod with equally spaced, raised vee-shaped teeth running parallel along its length (refer to the illustration). A hardened steel nut is designed to fit onto and move freely along the rod. The method of operation is that a hole slightly bigger than the small diameter of the rod is drilled into the broken screw. The rod is then lightly hammered into the hole. The raised teeth now bite into the metal surrounding the hole, producing a firm grip. The hexagonal nut is then placed onto the remaining portion of the rod protruding from the work. A ring spanner is used to turn the nut. It is important that the extractor is turned the right way, as these extractors can be used for right- and left-hand threads. The threads can be turned in the following directions while you are removing a broken bolt/stud: Right-hand thread – anti-clockwise Left-hand thread – clockwise. Straight screw extractor Thread Penetrants When you are disassembling components, it is often hard to remove some nuts and bolts. These fasteners have probably become corroded or seized to the thread. If extra leverage is applied to the spanner, the bolt or stud could shear off. To avoid this, apply a thread penetrant to the thread and allow it to stand for a period of time, generally overnight. Thread penetrant is very fine oil which seeps between the threaded parts and acts as a releasing agent by lubricating. It can make the removal of broken bolts and studs considerably easier. 2023-11-24 B-07b Maintenance Practices CASA Part 66 - Training Materials Only Page 170 of 498 Clamps and Vices The Vice Generally speaking, vices are used in conjunction with workbenches to carry out the many holding tasks in the workshop. Vices are usually classified into three main types: Bench Vices Bench vices are used to hold work for hand processing, e.g. marking out, shaping with hand tools and assembling small parts. Bench vice 2023-11-24 B-07b Maintenance Practices CASA Part 66 - Training Materials Only Page 171 of 498 Bench vice - sectional view Machine Vices Machine vices are used to hold components in position, in or on machines, so that operations may be performed on those components, e.g. drilling. Machine vices 2023-11-24 B-07b Maintenance Practices CASA Part 66 - Training Materials Only Page 172 of 498 Offset Vices Offset vices allow long, angular or wide work to be held vertically without obstruction from the moving jaw. Offset vices Vice Precautions Do not over-tighten the vice, which can damage both the work and the vice itself. Do not use hammers on any parts of the vice. Again, this will damage the vice. When operating any of the vices, keep hands clear of the vice jaws. Use the correct vice for the task and only in the manner for which it was designed. 2023-11-24 B-07b Maintenance Practices CASA Part 66 - Training Materials Only Page 173 of 498 Vice Jaws The vices discussed earlier are normally fitted with serrated, hardened steel jaws. To assist in the many different tasks that are undertaken in the workshop, different types of jaws are used. Standard Jaws Standard jaws are serrated, hardened steel jaws that are used for the many holding and gripping jobs that are carried out in the workshop. Standard jaws 2023-11-24 B-07b Maintenance Practices CASA Part 66 - Training Materials Only Page 174 of 498 Soft Jaws Soft jaws are manufactured from brass, aluminium or copper and used in conjunction with standard jaws when holding accurate or finished work. They protect the surfaces from the serrated jaws. Soft jaws 2023-11-24 B-07b Maintenance Practices CASA Part 66 - Training Materials Only Page 175 of 498 False Jaws False jaws are used to hold small circular work without damaging it. Some special tasks that are carried out regularly may require special false jaws that are manufactured and permanently fitted to vices in the workshop. False jaws 2023-11-24 B-07b Maintenance Practices CASA Part 66 - Training Materials Only Page 176 of 498 Clamps Many types and shapes of clamps are used in the engineering field to perform the same basic function of clamping. The type shown here is the toolmaker's clamp. Toolmaker's Clamp The toolmaker's clamp consists of two steel jaws held together with two long, fine-threaded screws which allow the jaws to be set at any distance apart. The toolmaker's clamp is used for holding small parallel work. Toolmaker's clamp 2023-11-24 B-07b Maintenance Practices CASA Part 66 - Training Materials Only Page 177 of 498 Surface Plates The basic requirement of any testing or measuring process is a precision flat surface. This surface becomes the datum point for measuring or serves as a plane on which other equipment may be set. Surface plates can be made from metal or granite. Surface plates are used for: Providing datum points when taking accurate linear or angular measurements Testing the degree of accuracy of other flat surfaces Setting up other precision testing equipment on a locating surface. Note: Always use surface plates with care. They are expensive and easily damaged. Surface plate 2023-11-24 B-07b Maintenance Practices CASA Part 66 - Training Materials Only Page 178 of 498 Surface Gauges The surface gauge shown below is a marking out tool. It may be used for: Marking out surfaces Setting up work for machining Checking work for parallelism Finding the centre of work Locating holes or surfaces from other surfaces. Note: As for scribers and dividers, the use of surface gauges is restricted. Surface gauge 2023-11-24 B-07b Maintenance Practices CASA Part 66 - Training Materials Only Page 179 of 498