18. NOTE: Most of these “locking nuts” are grouped together and are commonly referred to as prevailing torque nut s. This means the nut will hold its tightness or torque and not loosen with movement or vibration. Most prevailing torque nuts should be replaced whenever removed to ensure that the nut will not loosen during service. Always follow the manufacturer’s recommendations. Anaerobic sealers, such as Loctite , are used on the threads where the nut or cap screw must be both locked and sealed. ® Continued
19. Figure 8–8 Types of lock nuts. On the left, a nylon ring; in the center, a distorted shape; and on the right, a castle for use with a cotter key. Some nuts and cap screws use interference fit threads to prevent accidental loosening. The shape is distorted or a section of the threads is deformed.
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21. Figure 8–9 A typical bottoming tap used to create threads in holes that are not open, but stop in a casting, such as an engine block . Continued
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25. Figure 8–13 A die handle used to rotate a die while cutting threads on a metal rod. Continued
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28. A tap is a cutting tool, designed to cut new threads. A thread chaser has more rounded threads, designed to clean dirty threads without removing metal. When cleaning threads, it is best to use a thread chaser rather than a tap to prevent removing metal, which would affect the fit of the bolt. What is the difference between a tap and a thread chaser? Figure 8–15 A thread chaser is shown at the top compared to a tap on the bottom. A thread chaser is used to clean threads without removing metal.
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35. Figure 8–19 A typical door panel retaining clip. Figure 8–20 Plastic or metal trim tools are available to help the technician remove interior door panels and other trim without causing harm.
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40. There are also various self-locking nuts. Some have threads bent inward to grip the threads of the bolt. Some are oval-shaped at one end to fit tightly on a bolt. Fiber lock nuts have a fiber, plastic or nylon insert near the top of the nut or inside it. When the bolt turns through, it cuts threads in the fiber or plastic, putting drag on the threads to prevents loosening. Flat washers are placed underneath a nut to spread the load over a wide area and prevent gouging of the material. However, flat washers do not prevent a nut from loosening. Continued
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50. Figure 8–27 Helicoil kits, available in a wide variety of sizes, contain everything needed to repair a damaged hole back to its original size. ® To install Helicoil inserts, you need a thread repair kit. The kit includes a drill bit, tap, installation mandrel, and inserts. Repair kits are available for a wide variety of diameters and pitch to fit both American Standard and metric threads. ® A simple kit contains tooling a specific thread size. Master kits are available to cover a range of sizes. Continued
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