CHAPTER 4. Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION. Jones & Bartlett Learning, LL NOT FOR SALE OR DISTRIBUT

Transcription

1 CHAPTER 4..

2 Identifying Locking Devices 4 Primary Learning Objectives FOR After reading OR DISTRIBUTION this chapter, you will be able to: 1. Identify types of threads, nuts and bolts. (pp , 113) 2. Identify types of washers and screws. (pp , ) 3. Use a torque wrench to tension nuts. (pp ) 4. Identify pins and keys. (pp ) Knowledge Objectives After reading Jones this & chapter, Bartlett you Learning, will be able to: LLC 1. Identify FOR locking devices OR and DISTRIBUTION tools. (pp ) 2. Describe fasteners and torque. (pp ) 3. Identify locking device measuring tools. (pp ) 4. Describe helical inserts. (p. 119) 5. Identify locking pins and keys. (pp ) Skills Objectives After reading this chapter, you will be able to: 1. Use a torque wrench and torque angle gauge. (p. 119) PROCEDURE Remove and install split pins. (p. 119) PROCEDURE

3 108 CHAPTER 4 Identifying Locking Devices Introduction There are a number of special screws that cut their own threads as they go. This is called tapping a thread. Pictured FOR Locking devices OR DISTRIBUTION used in the motorcycle industry are primarily designed to hold things in a particular location material that cuts a mirror image of itself into the hole as in FOR FIGURE 4-4A is OR a self-tapping DISTRIBUTION screw. It is made of hard or to hold things together. These devices come in many you turn it. The screw in FIGURE 4-4B is also known as a forms, and depending on the particular application, one self-tapping screw, but it is designed for cutting and holding or more types of locking Jones devices & may Bartlett be used. Learning, They can LLC thin sheet metal, so it is often used Jones motorcycle & Bartlett bodies. Learning, LL be in the form of a physical FOR fastener and/or OR chemical DISTRIBUTION adhesive. This chapter provides a description of the types of locking devices found in motorcycle design. Locking Jones & Devices Bartlett Learning, and Tools LLC Fasteners There are many different fasteners used in motorcycle applications, including screws, bolts, studs and nuts. Jones & Washers Bartlett and Learning, chemical compounds LLC can be used to help FOR secure these OR fasteners. DISTRIBUTION A Screws Screws are generally smaller than bolts and are sometimes referred to as metal threads FIGURE 4-1. They can have a variety of heads, they re used on smaller components, and often their thread FOR extends right OR from DISTRIBUTION the tip to the head so they can hold together components of different thickness. Different screws can be tightened with a range of tools. An Allen Jones head screw & Bartlett has a recess Learning, for an Allen LLCwrench FIGURE 4-2. FOR An Allen head OR screw DISTRIBUTION is sometimes called a cap screw. It usually screws into a hole rather than a nut, and it needs tightening with an Allen wrench. A machine screw has a slot for a screwdriver B FIGURE 4-3. Screwdrivers come in many sizes and you Jones & should Bartlett always Learning, use the correct LLC size blade for the particular FOR machine screw OR DISTRIBUTION slot. FIGURE 4-2 A. An Allen head screw. B. Allen wrenches. FIGURE 4-1 Screws are generally smaller than bolts and are sometimes referred to as metal threads. FIGURE 4-3 A machine screw...

4 CHAPTER 4 Identifying Locking Devices 109 A Jones & TECHNICIAN Bartlett Learning, TIP LLC Threads are cut on screws, bolts, nuts and studs and inside holes to allow components to be attached and assembled. There was a time when there were many different thread designs used throughout the world. Modern motorcycles still use a Jones range of thread & Bartlett patterns, Learning, LL but due to standardization, it is getting FOR much simpler OR DISTRIBUT FIGURE 4-5. Nearly all the nuts, bolts, screws and studs on a motorcycle have a V-thread cut into them. A screw jack or a clamp has square threads cut into it. The square thread is more difficult to machine and is used mainly Jones in situations & Bartlett where rotational Learning, movement LLC needs to be transferred FOR into lateral OR movement for DISTRIBUTION example, the screw in a vise where the rotary movement of turning the handle is translated into the lateral movement of the jaws closing. Bolts, FOR Studs OR and DISTRIBUTION Nuts Bolts, studs and nuts are fasteners designed for heavier jobs than screws and tend to be made of metal or metal alloys. Bolts are cylindrical pieces of metal with a hexagonal head on one end and a Jones thread cut & Bartlett into the shaft Learning, LL at the other end FIGURE 4-6. They FOR are often bigger OR than DISTRIBUT screws and are used for heavier jobs. Bolts are always threaded into a nut or hole that has an identical thread cut inside. The thread acts as an inclined plane; as the bolt is turned, it is drawn into or out of the matching thread. B FIGURE 4-4 Self-tapping screws. Nuts are often used with bolts. A nut is a piece of metal, usually hexagonal, FOR with OR a thread DISTRIBUTION cut through it to fit the bolt thread. The hexagonal heads for the bolt and nut are designed to fit tools such as combination wrenches and sockets FIGURE 4-7. Acme thread Square thread 29 worm thread PJones & Bartlett Learning, LLC P P 29 o FOR OR DISTRIBUTION FOR o OR DISTRIBUT W W 29 F F D D D C C Standard thread shapes o FIGURE 4-5 Standard thread shapes...

5 110 CHAPTER 4 Identifying Locking Devices Thread pitch Bolt size Bolt head size FOR Bolt OR length DISTRIBUTION Bolt dimensions FIGURE 4-6 Bolt. FIGURE 4-7 Bolts usually have hexagonal heads. Torx drivers are used for torx bolts and are often found in motorcycle engines; they may be found in places such as cylinder heads to blocks, where particular tightening sequences are required FIGURE Jones 4-8. & Bartlett Learning, LL There are many different ways to FOR keep the nut and OR bolt DISTRIBUT done up tightly. A self-locking or Nylock nut can have a plastic or nylon insert. Tightening the bolt squeezes it into the insert, where it resists any movement. The self-locker is highly resistant to being loosened by the kind of vibra- tion that engines and motorcycles experience FIGURE 4-9. Tightening this style of nut distorts the insert, so it provides its locking effect only the first time you use it. If you remove the nut, it should be replaced with a new one. A castellated nut has slots like towers on a castle Jones FIGURE & 4-10 Bartlett. When Learning, it is screwed LLC onto a bolt that has FIGURE 4-8 Torx bolts are often found in motorcycle applications; they may be found in places such as cylinder heads to blocks, where particular tightening sequences are required. FIGURE 4-9 A self-locking nut is highly resistant to being loosened by vibrations...

6 CHAPTER 4 Identifying Locking Devices 111 A FIGURE 4-10 Castellated nut. Jones & been Bartlett drilled Learning, the right spot, LLCa split pin can be passed FOR through them OR DISTRIBUTION both and then spread open to lock the nut in place. Castellated nuts are used where scheduled maintenance requires inspection and adjustments to take place, for items such as front wheel bearings. A speed nut is not as Jones strong as & the Bartlett other types, Learning, but LLCB it can be a fast and convenient FOR way to secure OR DISTRIBUTION a screw FIGURE Once the speed nut is started, it does not need to be held. These are often used in places like body component fixings. Some bolts and nuts need washers. Washers can be made from Jones a number & Bartlett of materials Learning, depending LLCon their application, FOR including aluminum, OR DISTRIBUTION copper, fiber and steel. Here are some brief descriptions of the more common washers FIGURE 4-12 : Flat washers spread the load of a bolt head or a nut Jones & Bartlett as it is tightened Learning, and distribute LLC it over a greater area. C D FIGURE 4-11 Speed nut. FIGURE 4-12 Types of washers. A. Flat washer. B. Spring washer. C. Serrated edge shake-proof washers. D. Tab washer...

7 112 CHAPTER 4 Identifying Locking Devices This protects the surface underneath from being Jones & Bartlett marked Learning, by the nut or LLC head as it turns and tightens FOR down. OR Flat DISTRIBUTION washers should always be used to protect aluminum alloy. A spring washer compresses as the nut tightens, and the nut is spring loaded against this surface, which makes it unlikely Jones to work & Bartlett loose. The Learning, ends of LLC the spring washer also FOR bite into the metal. OR DISTRIBUTION Spring washers are used more for bolts and nuts. Screws mostly rely on smaller serrated edge shakeproof washers. The external ones have teeth on the Jones outside, & and Bartlett the internal Learning, ones have LLC teeth on the inside; FOR one type has both. OR DISTRIBUTION Tab washers get their name from these extensions. FIGURE 4-14 Bolts and nuts are often marked to indicate After the nut or bolt has been tightened, they remain how much torque can be safely applied to them. Markings exposed and are folded up to grip the flats and using the metric system are shown here. Jones & Bartlett prevent Learning, movement. LLC FOR Often, the OR thread DISTRIBUTION on a stud is only as long as it needs to be to tighten onto the nut or into the threaded hole. Some special versions have both a left- and right-hand thread pitch, length and grade. The diameter is measured across the outside of the threads; it is measured thread on them. A stud is like two bolts in one; for instance, an exhaust manifold on the cylinder head is in fractions of an inch for standard-type fasteners, and normally located and held by studs and nuts. millimeters for metric-type fasteners. A 3/8 (9.5-mm) A stud does not have a fixed hexagonal head; rather, it bolt has a thread diameter of 3/8 FOR (9.5 mm); 3/8 OR is not DISTRIBUT has a thread cut on each end FIGURE It is threaded the size of the bolt head. into one part, where it stays. The mating part is then The metric system uses numbers stamped on the heads slipped over it and a nut is threaded onto the end of of metric bolts and on the face of metric nuts FIGURE the stud Jones to secure & the Bartlett part. Studs Learning, are commonly LLC used to Even studs have Jones a marking & Bartlett system to Learning, make sure they LLCare attach a throttle FOR body to the OR intake DISTRIBUTION manifold. Studs can not over-stressed FOR when you tighten OR them. DISTRIBUTION The numbers have different threads on each end. indicate the tensile strength of the bolt. Tensile strength Bolts, nuts and studs can have either standard or metric refers to how much tension it can withstand before it threads. They are designated by their thread diameter, breaks. The number does not mean the size of the bolt. Note: The distance between flats on the bolt or nut heads Jones generally & Bartlett indicates Learning, wrench size to LLC be used. FOR The imperial OR system DISTRIBUTION also uses a marking system to indicate tensile strength, as shown in FIGURE This is a grade 5 bolt, and can be tightened to specific torque as specified by the manufacturer. The dots on this nut, also a grade 5, give similar information. The coarseness of any thread is called FOR its thread OR pitch. DISTRIBUT In the standard system, bolts, studs and nuts are measured in threads per inch (tpi). To determine the tpi, simply count the number of threads there are in 1 inch. Each bolt diameter in the standard system can have one of FIGURE 4-13 A stud has threads on each end. two thread pitches, Jones coarse & Bartlett (UNC) Learning, or fine (UNF). LLCFor example, a 3/8-16 FOR is coarse, while OR a DISTRIBUTION 3/8-24 is fine. In the metric system, the thread pitch is measured by the distance between the peaks of the threads in millimeters FIGURE Each bolt diameter in the metric system can have up to four thread pitches. Metric threads, designated..

8 CHAPTER 4 Identifying Locking Devices 113 with a capital M, are rated according to their outer diameter and their pitch. FOR The length of OR a bolt DISTRIBUTION is fairly straightforward. It is measured from the end of the bolt to the bottom of the head and is listed in inches or millimeters. The grade of a fastener relates to its strength. The higher the grade number, the higher the tensile Jones strength. & Tensile Bartlett strength Learning, LL for fasteners is generally listed in pounds FOR per square OR inch DISTRIBUT of bolt shaft area. Tensile strength for metric fasteners is generally listed in megapascals, or MPa, of bolt shaft area. A metric bolt marked on the head as 10.9, for example, would have an approximate yield strength of 90% of 1,000 MPa. FIGURE 4-15 Tensile strength markings using the imperial system Grade 5 bolt. TECHNICIAN TIP Jones While & US Bartlett and some Learning, other manufacturers LLC use the imperial system of inch-pounds, the global version of metric is called the International System of Units, or SI. No. of threads per inch The metric system has produced some competing 1 Inch classifications for fasteners. For example, metric hex cap screws may have three different Jones standards: & Bartlett Learning, LL 1. DIN 931 (DIN 933 fully threaded) Diameter of bolt in inches 2. ISO 4014 (ISO 4017 fully threaded) A 3. ANSI/ASME B M These three Jones standards & are Bartlett interchangeable, Learning, differing LLC primarily in the width FOR across the OR flat dimensions. DISTRIBUTION TECHNICIAN TIP Distance between the peaks in millimeters Many motorcycle bolts and nuts need to be tightened to a specified level tight enough to hold components together but not so tight that the component or the Diameter of fastener could fail. This level of tightness is called bolt the torque specification. Bolts Jones and nuts are & Bartlett often Learning, LL millimeters marked with grades to tell you their strength, which determines how much torque can safely be applied to them. For example, a grade 8 bolt is stronger than a grade 5 bolt and can be tightened to a higher torque. The specific torque required for every bolt B on the motorcycle Jones should & Bartlett always be Learning, obtained from LLC FIGURE 4-16 A. In the standard system, the thread pitch is measured in threads per inch (tpi). B. In the metric system, the thread pitch is measured by the distance between the peaks of the threads in millimeters. the manufacturer s FOR technical information OR DISTRIBUTION system. Once bolts are tightened, there are different ways to ensure they stay tight. For example, a locking washer, a locking chemical compound or a nylon locking device built into the nut may be used...

9 114 CHAPTER 4 Identifying Locking Devices Jones Fasteners & Bartlett Learning, and Torque LLC Fasteners are designed to secure parts that are under various tension and shear stresses. The nature of the stresses placed on parts and fasteners depends on their use and location. For example, head bolts withstand tension stresses by clamping the Jones head gasket & Bartlett between Learning, the LL cylinder head and the block. The bolts FOR must withstand OR the DISTRIBUT very high combustion pressures trying to push the head off the engine block in order to leak past the head gasket. An example of fasteners withstanding shear stresses is wheel studs and Jones wheel & nuts Bartlett on a quad. Learning, They clamp LLCthe wheel assembly to FOR the suspension OR system, DISTRIBUTION and the weight of the quad tries to shear the lug studs. If this were to happen, the wheel would fall off the quad, leading to FIGURE 4-17 Applying a chemical compound such as Loctite an accident. to the threads helps prevent fasteners from loosening. To accomplish their job, fasteners come in a variety Jones of diameters & Bartlett and Learning, hardnesses, LLC which are defined in tensile FOR strength OR grades. DISTRIBUTION Fasteners with screw threads Chemical Compounds are designed to be tightened to a specific torque depending on the job at hand, the tensile strength Chemical compounds (such as Loctite) help prevent or hardness of the material they are made from, their fasteners from loosening FIGURE They are applied size and the thread pitch. If a fastener is overtightened, it could become damaged or could break. If it is to one thread, and then Jones the other & Bartlett is screwed Learning, onto it. LLC This creates a strong bond between FOR them, OR but one DISTRIBUTION that undertightened, it could work loose over time. Torque stays plastic, so in the future they can be separated with is a way of defining how much a fastener should be a wrench if necessary. tightened. Some metals react with each other and bind together for instance, Jones spark & Bartlett plugs when Learning, they are in LLC aluminum Torque Charts cylinder heads. FOR An anti-seize OR compound DISTRIBUTION neutralizes the chemical reaction that can make this happen and prevents Torque specifications for bolts and nuts in motorcycles will usually be contained within workshop man- threads and fasteners from sticking together FIGURE uals. Bolt, nut and stud manufacturers also produce torque charts, which contain all the information you Jones need & to Bartlett determine Learning, the maximum LLCtorque of bolts or nuts FOR FIGURE 4-19 OR. For DISTRIBUTION example, most charts include the bolt diameter, threads per inch (or mm), grade and maximum torque setting for both dry and lubricated bolts and nuts. A lubricated bolt and nut will reach maximum torque value at a lower setting. In practice, most torque specifications call for the nuts and bolts to have dry threads prior to tightening. FOR There are OR some DISTRIBUT exceptions, so close examination of the torque specification chart is critical. FIGURE 4-18 Applying an anti-seize compound prevents threads and fasteners from sticking together. Friction Friction is a force that resists the movement of one surface over another. It can be desirable in some cases and not desirable in others. For instance, locking devices rely on friction to hold them together Jones and in & place, Bartlett whereas Learning, an engine LLCrequires the least..

10 CHAPTER 4 Identifying Locking Devices 115 In the absence of torque specifications the values below can be used as a guide to the maximum safe torque for a specific diameter/grade of fastener. The torque specification is for clean dry threads, if the threads are oiled reduce the torque by 10%. Bolt Grade Marking Bolt Diameter FOR 4.6 OR DISTRIBUTION Maximum Torque Maximum Torque Maximum Torque lb ft Nm lb ft Nm lb ft Nm Maximum Torque Maximum Torque lb ft Nm lb ft Nm M M M M Jones & Bartlett M10Learning, 14 LLC M Jones 37 & Bartlett 50 Learning, LLC M M16 M M M FIGURE 4-19 Torque specification chart. Jones & friction Bartlett possible Learning, and relies LLC on the lubrication system Jones tires do & not Bartlett slide easily Learning, when you LLCapply the brakes or FOR to prevent OR friction. DISTRIBUTION turn FOR into a corner. OR DISTRIBUTION Friction is caused by surface rough spots that lock together. These spots can be microscopically small, Locking Device which is why even surfaces that seem to be smooth can experience friction. Friction Jones can & be Bartlett reduced but Learning, never LLC Measuring Tools eliminated. Torque Wrenches Friction is always measured for pairs of surfaces, using what is called a coefficient of friction. A torque wrench is also known as a tension wrench A low coefficient of friction for a pair of surfaces means FIGURE It is used to tighten fasteners to a predetermined torque. It is designed to tighten bolts and nuts they can move easily over each other. Ice and metal have a low coefficient Jones & of Bartlett friction, so Learning, metal ice skates LLC slide easily on ice. FOR OR DISTRIBUTION and accessory of FOR the same drive OR size DISTRIBUTION found in an ordi- using the drive Jones on the & end, Bartlett which Learning, fits with any LLC socket A high coefficient of friction for a pair of surfaces nary socket set. Although manufacturers do not specify means they cannot move easily over each other. Rubber torque settings for every nut and bolt, it is important to tires and dry road surfaces have a high coefficient of follow the specifications when they do. For example, Jones & friction, Bartlett so they Learning, tend to grip LLCeach other. That means Jones manufacturers & Bartlett specify Learning, a torque for LLCcylinder head bolts...

11 116 CHAPTER 4 Identifying Locking Devices The torque specified will ensure that the bolt provides the proper clamping pressure and will not come loose, but will not be so tight as to risk breaking the bolt or placed at the end of a 1-inch-long lever. Also note that 1 lb-ft equals 12 in-lb. A newton meter is described as the FOR amount of twisting OR DISTRIBUTION force applied to a shaft by a perpendicular lever 1 meter long with a force of 1 newton applied to the outer end. A torque value of 100 Nm will be the same as applying a 100-newton force to the end of a 1-meter-long lever. (One lb-ft Jones is equal & to Bartlett 1.35 Nm.) Learning, LL Torque wrenches come in various FOR types: beam OR style, DISTRIBUT clicker, dial and electronic FIGURE The simplest and least expensive is the beam-style torque wrench. It uses a spring steel beam that flexes under tension. A smaller fixed rod then indicates the amount of torque on a scale mounted to the bar. The amount of deflection of the bar coincides with the FOR amount of torque OR DISTRIBUTION on the scale. One drawback of this design is that you have to be positioned FIGURE 4-20 The torque wrench has an adjustable handle, directly above the scale so you can read it accurately. which allows technicians to adjust to the correct torque That can be a problem when working in confined spaces. specification for the job. Jones The & clicker-style Bartlett Learning, torque wrench LLCuses an adjustable clutch FOR inside that OR slips DISTRIBUTION (clicks) when the preset torque is reached. You can set it for a particular torque on the handle. As the bolt is tightened, once the preset torque is reached, the torque wrench will click. This makes it especially handy in situations where the scale of a beam-style stripping the threads FIGURE torque wrench cannot be read. The higher the torque, The torque value will be specified FOR in foot-pounds OR DISTRIBUTION (lb-ft), the louder the click; the lower the torque, FOR the quieter OR the DISTRIBUT inch-pounds (in-lb), or newton meters (Nm). The torque click. Be careful when using this style of torque wrench, value is the amount of twisting force applied to a fastener especially at lower torque settings. It is easy to miss the by the torque wrench. A foot-pound is described as the click and overtighten, break or strip the bolt. Once the amount Jones of twisting & Bartlett force applied Learning, to a shaft LLC by a perpendicular lever FOR 1 foot long with OR a weight DISTRIBUTION of 1 pound placed on the outer end. A torque value of 100 lb-ft will be the same as a 100-lb weight placed at the end of a 1-foot-long lever. A torque value of an inch-pound will be 1 pound torque wrench Jones clicks, stop & Bartlett turning it, Learning, as it will continue LLC to tighten the fastener FOR if you turn OR it past DISTRIBUTION the click point. The dial torque wrench turns a dial that indicates the torque based on the torque being applied. Like the beam-style torque wrench, you have to be able to see the dial to know how much torque is being applied. Many dial torque wrenches FIGURE 4-21 The torque wrench is fitted over the wheel locking nuts and tightened to the specified torque. FIGURE 4-22 Torque wrench...

12 CHAPTER 4 Identifying Locking Devices 117 have a movable indicator that is moved by the dial and stays the fastener increases. Tightening a rusty fastener to a particular torque will not provide as much clamping force as at the highest reading. That way, you can double-check the FOR torque achieved OR DISTRIBUTION once the torque wrench is released. Once a FOR smooth fastener OR torqued DISTRIBUTION the same amount. All threads the proper torque is reached, the indicator can be moved must be clean before tightening the fastener to a specified back to zero for the next fastener being torqued. torque. This also brings up the question of whether threads The digital torque wrench usually uses a spring steel bar should be lubricated. In most motorcycle cases, the torque with an electronic strain Jones gauge to & measure Bartlett the amount Learning, of LLC values specified are for dry, non-lubricated Jones & Bartlett threads, Learning, but LL torque being applied. The torque FOR wrench can be OR preset DISTRIBUTION to the always check the manufacturer s specifications. FOR OR DISTRIBUT desired torque. It will then display the torque as the fastener When bolts are tightened, they are also stretched. As is being tightened. When it reaches the preset torque, it will long as they are not tightened too much, they will return usually give an audible signal, such as a beep. This makes to their original length when loosened. This is called it useful in situations where a scale or dial cannot be read. elasticity. If they continue to be tightened and stretch Torque wrenches fall out of calibration over time or beyond their point of elasticity, they will not return to if they are not FOR used properly, OR so DISTRIBUTION they should be checked their original length FOR when loosened. OR DISTRIBUTION This is called the and calibrated annually. This can be performed in the yield point. Torque-to-yield (TTY) means that a fastener workshop if the proper calibration equipment is available, is torqued to, or just beyond, its yield point. or the torque wrench can be sent to a qualified service With the changes in engine metallurgy that manufacturers are & using Bartlett in modern Learning, motorcycles, LLCbolt technology has Jones & center. Bartlett Most Learning, quality torque LLC wrench manufacturers provide a recalibration OR DISTRIBUTION service for their customers. had FOR to change as OR well. DISTRIBUTION To help prevent bolts from loosen- Jones FOR ing over time and to maintain an adequate clamping force when the engine is both cold and hot, manufacturers have adopted stretch or torque-to-yield (TTY) bolts. TTY Using a Torque Wrench and a Torque Angle Gauge To help ensure that the proper amount of torque gets from bolts are designed to provide a consistent clamping force the torque wrench to the bolt, support the head of the torque when torqued to their yield point or just beyond. The wrench with one hand FOR FIGURE When using OR DISTRIBUTION a torque challenge is that the torque does not FOR increase very OR much, DISTRIBUT wrench, it is best not to use extensions. Extensions make or at all, once yield is reached, so using a torque wrench by it harder to support the head, which can end up absorbing itself will not indicate the point at which the manufacturer some of the torque. If possible, use a deep socket instead. wants the bolt tightened. Consequently, TTY bolts generally Torque Jones is not always & Bartlett the best Learning, method of LLC ensuring that a bolt is tightened FOR enough OR to give DISTRIBUTION the proper amount of clamping force. If the threads are rusty, rough or damaged in any way, the amount of twisting force required to tighten require a new torqueing Jones & procedure Bartlett called Learning, torque angle. LLCIt is important to note that, FOR in virtually OR all cases, DISTRIBUTION TTY bolts cannot be reused because they have been stretched into their yield zone and would very likely fail if re-torqued. Always check the manufacturer s specifications when doing this as some manufacturers say that the bolt must be changed Jones once a & maximum Bartlett length Learning, has been LLC reached. FOR Torque angle OR is considered DISTRIBUTION a more precise method to tighten TTY bolts and is essentially a multistep process. Bolts are first torqued in the required pattern using a standard torque wrench to a required moderate torque setting FIGURE They are then further tightened an Safety FIGURE 4-23 Ensure the proper amount of torque gets from the torque wrench to the bolt by supporting the head of the torque wrench with one hand. For your safety: Refer to the Jones manufacturer s & Bartlett specifications Learning, when LLC tightening fasteners. FOR OR DISTRIBUTION Return the torque wrench to its lowest setting when finished. If replacing a fastener, make sure it has the correct Jones tensile & Bartlett value for Learning, the task it will LLC perform...

13 118 CHAPTER 4 Identifying Locking Devices To use a torque wrench and torque angle gauge, follow the guidelines in PROCEDURE 4-1. Helical Inserts No matter how strong a bolt is, Jones it can break. & Bartlett There are Learning, a LL number of techniques used to remove FOR broken bolts OR and DISTRIBUT repair threads. Those techniques will be demonstrated later in this series. One of the tools used to repair damaged bolt holes are helical inserts, more commonly known by their trademark Helicoil FIGURE Helicoils are made of coiled Jones wire and & are Bartlett inserted Learning, into a tapped LLC hole that is larger than FOR the desired hole. OR DISTRIBUTION Helicoils are selfanchoring, and special tools are required to install them. FIGURE 4-24 Torque sequence. Once in place, a new bolt or spark plug is threaded into the helicoil insert. FOR additional OR specified DISTRIBUTION angle (torque angle) using an angle Locking Pins and Keys gauge, thus providing further tightening to tighten the bolt to, or beyond, its yield point. In some cases, after A split pin is used to secure other fasteners, typically torqueing, the manufacturer first wants all of the bolts castellated nuts FIGURE Split pins are often made to be turned to an initial Jones angle, and & then Bartlett turned Learning, an additional angle FIGURE In other cases, the manufacturer LLC of soft metal, making them easy Jones to install & Bartlett or remove. Learning, LL They should never be used more FOR than once, and OR they DISTRIBUT wants all of the bolts torqued in a particular sequence, should not be used in applications where there are then de-torqued in a particular sequence, then re-torqued strong shearing forces at play. Split pins are also used once again in a particular sequence and finally tightened to keep other components, such as washers, from coming off shafts. an additional specified angle. You must therefore always check the Jones manufacturer s & Bartlett specifications Learning, and LLC procedure To remove and Jones install & split Bartlett pins, follow Learning, the guidelines LLC before torqueing FOR TTY bolts. OR DISTRIBUTION in PROCEDURE 4-2 FOR. OR DISTRIBUTION FIGURE 4-25 Angle gauge. FIGURE 4-26 Helicoils...

14 CHAPTER 4 Identifying Locking Devices 119 FOR PROCEDURE OR DISTRIBUTION 4-1 Using a Torque FOR Wrench OR DISTRIBUTION and Torque Angle Gauge 1 Identify the stretch bolt either Jones through the & Bartlett Learning, LL manufacturer s specifications or, in some cases, stretch bolts themselves have a specific marking on the head of the bolt. In addition, the diameter of the shank of the bolt is thinner than the threaded diameter. 2 Check the specifications. Determine the correct torque value Jones and sequence & Bartlett for the bolts Learning, or fastener LLC you are using. FOR This will be in foot-pounds OR DISTRIBUTION or newton meters (Nm). Also check the torque angle specifications for the bolt or fastener, and whether the procedure is one step or more than one step. Jones 3 Tighten & Bartlett the bolt to Learning, the specified LLC torque. If the FOR component requires OR DISTRIBUTION multiple bolts or fasteners, make sure to tighten them all to the same torque value in the sequence and follow the steps that are specified by the manufacturer. Some torqueing procedures could call for a number of steps to complete the torqueing process. For example, motorcycle specifications Jones & as follows: Bartlett Learning, LL a. Step 1: Torque bolts to 29.5 foot-pounds, FOR or OR DISTRIBUT 40 newton meters (Nm). b. Step 2: Torque bolts to 44 foot-pounds, or 60 newton meters (Nm). c. Step 3: Jones Finally, tighten & Bartlett the bolt a Learning, further 90 degrees. LLC PROCEDURE 4-2 Removing Jones and & Bartlett Installing Learning, Split LLCPins 1 Ensure you have the correct size of split pin for the relevant hole size. 2 Use an appropriate pair of pliers to straighten the legs of the split pin. 4 Grip the pin head and pull it out of the nut or bolt. 4 Make the required repair/adjustment and reassemble and adjust accordingly. 5 Insert the Jones new pin, legs & Bartlett first, as far as Learning, it will go. LLC 6 Bend the legs back and cut them to the required size if necessary...

15 120 CHAPTER 4 Identifying Locking Devices FIGURE 4-27 Split pins. Rawl pins FIGURE 4-28 Jones & Bartlett Learning, are often LLCused to hold components on rotating shafts. They are a type of shear pin, used when excessive force is used to avoid further damage to a component. They are normally made from a spring-type steel. Locking Keys Keys are used to prevent the free FOR rotation of gears OR DISTRIBUT or pulleys on a shaft FIGURE Keys come in various shapes depending on their use: Parallel keys, for example, can be used to secure a gear wheel Jones its & shaft Bartlett FIGURE Learning, LLC Taper keys FOR are used to anchor OR DISTRIBUTION a pulley to a shaft or a disc to a driving shaft FIGURE A feather key is usually attached to levers that have to slide along a shaft to allow engagement of a part Jones FIGURE & Bartlett A Learning, feather key LLC is an extra component FOR Locking OR Pins DISTRIBUTION FOR used with OR a shaft-to-collar DISTRIBUTION connection. The connection is positive fitting and serves to transmit Dowel pins are used to keep components in place where shearing forces are high. For example, they are used in torques and revs, for example, on the driveshaft of high-pressure pumps to keep valve plates anchored in a belt pulley. position. Pins should never be directly struck by a hammer; a pin punch should be FOR used instead. OR DISTRIBUTION ily and are used when a gear FOR or a pulley has OR to be DISTRIBUT Gibb-head keys are designed Jones to be & pulled Bartlett out eas- Learning, LL Taper pins are used to position parts on a shaft, for attached to a shaft FIGURE example gears, pulleys and collars. They are steel rods with one end having a slightly larger diameter than the other. Keyway Key FOR Keyseat OR DISTRIBUT FIGURE 4-28 Rawl pins. FIGURE 4-29 Locking keys...

16 CHAPTER 4 Identifying Locking Devices 121 FIGURE 4-30 Parallel keys. FIGURE 4-32 Peg feather key. FIGURE 4-31 Taper key. FIGURE 4-33 Gibb-head key...

17 122 CHAPTER 4 Identifying Locking Devices Vocabulary Builder and Review Questions Vocabulary Builder imperial system Bolts, nuts and studs can have either imperial or metric threads. They are designated by their Allen head screw Sometimes called a cap screw, it has a thread diameter, thread pitch, length and grade. Imperial hexagonal recess in the head Jones which & fits Bartlett an Allen Learning, wrench. LLC measures are in feet, inches and fractions of inches. The This type of screw usually anchors FOR components OR DISTRIBUTION in a predrilled hole. United States uses the imperial system, but most countries use the metric system. anti-seize compound Neutralizes a chemical reaction machine screw A screw with a slot for screwdrivers. that can prevent threads and fasteners from sticking together and freeze spark plugs place in aluminum nut A fastener with a hexagonal head and internal cylinder blocks. threads for screwing on bolts. bolt A type of threaded fastener with a thread on one Nylock nut Keeps the nut and bolt done up tightly; can end and a hexagonal head on the other. have a plastic or nylon insert. Tightening the bolt squeezes it into the insert, where it resists any movement. The castellated nut A nut with slots, similar to towers on a self-locker is highly resistant to being loosened. Jones & castle, Bartlett that is Learning, used with split LLC pins; it is used primarily to secure wheel bearings. parallel keys Used to prevent the free rotation of gears or FOR pulleys on a OR shaft DISTRIBUTION and can be used to secure a gear chemical compound Helps prevent fasteners from loosening; it is applied to one thread, then the other fastener wheel on its shaft. is screwed onto it. This creates a strong bond between rawl pins Often used to hold components on rotating shafts. They are a type of shear pin, used when them, but one that stays plastic, so they can be separated by a wrench. excessive force is used to avoid Jones further & Bartlett damage to Learning, a LL component. dowel pins Used to keep components in place where shearing forces are high, such as valve plates on highpressure pumps. screws Usually smaller than bolts and are sometimes referred to as metal threads. They can have a variety of heads, and are used on smaller components. The thread elasticity The amount of stretch or give a material has. often extends Jones from the & tip Bartlett to the head Learning, so they can LLC hold fasteners Devices FOR that securely OR DISTRIBUTION hold items together, such together components FOR of variable OR thickness. DISTRIBUTION as screws, cotter pins, rivets and bolts. self-tapping screw A screw that cuts down its own feather key Used to prevent the free rotation of gears thread as it goes. It is made of hard material that cuts a or pulleys on a shaft; usually attached to levers that have mirror image of itself into the hole as you turn it. to slide along a shaft to allow engagement of a part. The Jones & connection Bartlett is Learning, a positive fitting LLC and serves to transmit Jones serrated & Bartlett edge shake-proof Learning, washer LLC A washer that is FOR torques and OR revs for DISTRIBUTION example, on the driveshaft of used to anchor smaller screws. a FOR OR DISTRIBUTION belt pulley. shear stress The form of stress that tends to produce cutting rather than stretching or bending. flat washers Spread the load of a bolt head or a nut as it is tightened and distribute it over a greater area. They speed nut A nut usually made of thin metal; it does not are particularly useful in Jones protecting & Bartlett aluminum Learning, alloy. LLC need to be held when started but Jones it is not & Bartlett as strong as Learning, a LL conventional nut. A fast and convenient way to secure friction A force that resists the FOR movement of OR one DISTRIBUTION surface a screw. over another, caused by surface rough spots that lock together. Kinetic friction is resistance to motion when one spring washer A washer that compresses as the nut surface moves over another. Static friction is resistance tightens; the nut is spring loaded against this surface, to motion between two surfaces that are not moving. which makes it unlikely to work loose. The ends of the Friction is always measured for pairs of surfaces, using spring washer also bite into the metal. a coefficient of friction. square thread A thread type with square shoulders used Gibb-head key Used to prevent the free rotation of gears or to translate rotational to lateral movement. pulleys on a shaft; designed to be pulled out easily and are stud A type of threaded fastener with a thread cut on used when a gear or a pulley has to be attached to a shaft. each end, as opposed to having a bolt head on one end...

18 CHAPTER 4 Identifying Locking Devices 123 tab washer A washer that gets its name from the torque angle A method of tightening bolts or nuts based small tabs that are folded back to secure the washer. on angles of rotation. FOR After the nut OR or DISTRIBUTION bolt has been tightened, they remain torque specification Describes the amount of twisting exposed and are folded up to grip the flats and prevent force allowable for a fastener or a specification showing movement. the twisting force from an engine crankshaft; supplied taper key Used to prevent the free rotation of gears or by manufacturers. pulleys on a shaft; used Jones to anchor & a Bartlett pulley to Learning, a shaft or LLC torque-to-yield A method of Jones tightening & Bartlett bolts close Learning, to LL a disc to a driving shaft. their yield point or the point at which FOR they will not OR return DISTRIBUT taper pins Used to position parts on a shaft, for example to their original length. gears, pulleys and collars. torque-to-yield (TTY) bolts Bolts that are tightened tensile strength In reference to fasteners, the amount using the torque-to-yield method. of force Jones it takes before & Bartlett a fastener Learning, breaks. LLC torque wrench Jones A tool & used Bartlett to measure Learning, the rotational LLCor thread pitch FOR The coarseness OR or DISTRIBUTION fineness of a thread as twisting force applied FOR to fasteners. OR DISTRIBUTION measured by either the threads per inch or the distance torx bolt Often found in motorcycle engines in places from the peak of one thread to the next. Metric fasteners such as cylinder heads to blocks, where particular tightening sequences are required. are measured in millimeters. Jones & torque Bartlett The amount Learning, of twisting LLCforce applied in a turning Jones yield & point Bartlett The point Learning, at which LLC a bolt is stretched so FOR application, OR usually DISTRIBUTION measured in foot-pounds or newton hard FOR that it fails; OR it is DISTRIBUTION measured in pounds per square meters. inch of bolt cross-section...

19 124 CHAPTER 4 Identifying Locking Devices Jones Review & Bartlett Questions Learning, LLC 6. Tech A says that torque values are measured in footpounds. Tech B says that torque values are measured 1. Tech A says that a hex bolt is usually used in conjunction with a flat nut. Tech B says that a split pin FOR in newton meters. OR DISTRIBUTION Who is correct? a. Tech A is usually used in conjunction with a castellated nut. b. Tech B Who is correct? a. Tech A b. Tech B c. Both A and B d. Neither A nor B c. Both A and B d. Neither A nor B 2. Bolts are usually used for heavier jobs than screws. a. True Jones & Bartlett Learning, LLC b. FalseFOR OR DISTRIBUTION 3. Tech A says that studs are commonly used to attach a throttle body to the exhaust manifold. Tech B says that studs are commonly used to attach a throttle Jones & Bartlett body to the Learning, intake manifold. LLC Who is correct? FOR a. Tech OR ADISTRIBUTION b. Tech B c. Both A and B d. Neither A nor B 7. Tech A says that shaft strength refers to the amount of force a bolt can take before it breaks. Tech B says that tensile strength refers to the amount of force a bolt can take before it breaks. Who is correct? a. Tech A Jones & Bartlett Learning, LLC b. Tech B FOR OR DISTRIBUTION c. Both A and B d. Neither A nor B 8. Keys are used to prevent the free rotation of gears or Jones pulleys & Bartlett on a shaft. Learning, LLC a. True b. False 9. Thread pitch is the measurement from the peak of one thread to the next and indicates the coarseness 4. When you tighten a Jones cylinder & head Bartlett bolt, the Learning, tightening sequence does not matter. FOR OR DISTRIBUTION LLC or fineness of the thread. a. True a. True b. False b. False 10. The number stamped on the head of a bolt indicates 5. A torque angle gauge shows you the correct tightening Jones specifications & Bartlett when you Learning, are tightening LLCa bolt. its size. a. True a. True b. False b. False..

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