Fastenerstfss3
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    Fastenerstfss3 Fastenerstfss3 Presentation Transcript

      • "No man will make a great leader who wants to do it all himself, or to get all the credit for doing it."
      • Andrew Carnegie
    • UNIT 2.10
      • When completed the student will understand:
      • Purpose and need of fasteners
      • Fasteners Identification
      • Fastener grading
      • Fastener types
      • Torque to Yield
      • Torque Sequence
      • Thread Repair
      • Why do we need fasteners?
      • To attach parts and components.
      • Why do we need to know about fasteners?
      • To ensure proper usage
      • Correct Torque
      • To perform proper repairs
      • Bolt
      • Screw (Self Tapping)
      • Hex Nut
      • Wing Nut
      • Pop Rivet
    •  
      • Diameter
        • Measured across the threaded area
      • Thread pitch (English system)
        • The number of threads per inch
      • Thread pitch (Metric system)
        • The distance in millimeters between two adjacent threads
    •  
      • A metric size bolt that is identified as
      • 6mm x 30mm x 1.25mm:
        • Has a shank diameter of 6 millimeters.
        • Is 30 millimeters long from the bottom of the head to the end of the shank.
        • Has a distance of 1.25 millimeters between its threads.
      • There are three basic types of threads used on fasteners:
      • Coarse threads
        • UNC-Unified National Coarse
      • Fine threads
        • UNF-Unified National Fine
      • Metric threads
        • SI
      • Also called tensile strength
      • Refers to the amount of pull a fastener can withstand before breaking
      • Bolt head markings specify the tensile strength of the bolt
      • U.S. customary bolts are marked with lines
      • Metric bolts are marked with numbers
    •  
    •  
      • There are millions of different fasteners.
    •  
      • NUT TYPES
      • Castle Nuts and Cotter Pins
      • Cotter Pins keep nuts from turning and possibly coming loose.
      • WASHER TYPES
      • Flat washer
        • increases the clamping surface under the fastener
        • prevents the bolt or nut from digging into the part
      • Lock washer
        • prevents the bolt or nut from becoming loose under stress and vibration
      • A. Plain flat washer
      • B. Split lock washer
      • C. Toothed lock washer
      • D. Lock plate
      • SNAP RINGS
      • Fits into a groove in a part and commonly holds shafts, bearings, gears, pins, and other components in place
      • Snap ring pliers are needed to remove and install a snap ring
        • special jaws grasp the snap ring
    •  
      • Key (A)
        • prevents a part from turning on its shaft
        • fits into a keyseat (slot) cut into a shaft and a keyway cut into the mating part
      • Set screw (B)
        • normally used to lock a part onto a shaft
        • not as strong as a key
      • Requires a bolt to be tightened to a specific torque and then turned an additional number of degrees
      • Procedure stretches the bolt to its correct yield point, preloading the fastener for better clamping under varying conditions
      • New bolts may be required each time
      • Used to make sure that parts are fastened evenly
      • Creates an even, gradual clamping force along the entire mating surface of the parts
      • Crisscross pattern is often recommended
      • MINOR THREAD REPAIRS
      • Minor thread damage includes nicks, partial flattening, and other less serious problems
      • Minor damage can be repaired with a thread chaser or a thread file
        • the thread chaser is run through or over the threads to restore them
      • MAJOR THREAD REPAIRS
      • Badly smashed or stripped threads may be repaired with either a tap or die
      • Tap
        • threaded tool for cutting internal threads in holes
      • Die
        • cuts external threads on metal rods, bolts, shafts, and pins
    •  
      • Hold the handle squarely with the work
      • Back the handle off to clean metal out of the threads
      • Use a taper tap to start the threads
      • Use a plug tap and a bottoming tap to cut the threads to the bottom of the hole
      • Never force a tap handle or the tool may break
      • Keep the tap and die well oiled to ease cutting
      • Use coarse threads when threading or tapping into soft metal, like aluminum
        • coarse threads will hold better than fine threads
    •  
      • When threads cannot be restored, the hole can be drilled and tapped oversize
      • Use a “drill and tap size chart” to choose a drill bit and tap
      • Drill the hole one size larger than the original hole
      • Cut new threads in the drilled hole
      • Use a larger bolt in the threaded hole
    •  
      • A. Drill the
      • hole oversize
      • B. Tap the
      • hole oversize
      • C. Mount the
      • insert on a mandrel
      • D. Thread the
      • insert into the hole
    •  
    •