Threads and Fasteners

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Threads and Fasteners
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Purpose

• To fasten objects together
• Common Fasteners
• Nuts bolts
• Tapers
• Rivets
• Screws
• Nails

• Machine screws
• Locking pins
• Adhesives
• Keys

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Threads

• Course Threads, Fine Threads, Metric threads and
  whitworth.
• Course and fine are common imperial
• Metric is common
• Whitworth is the old British standard

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Course Threads

• Threads farther apart
• Deeper cut
• Best used with soft materials
• Aluminum
• Brass
• Copper
• Plastic

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Fine Threads

• Threads closer together
• More thread contact for length
• Common in harder metals

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Metric

• Has similar course and fine types
• Measured differently
• Different head markings

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Whitworth Threads

• Only found in old British cars
• 55 thread instead of standard 60

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Thread classification

• UNC Unified national course
• UNF Unified national fine
• Standard measurement
• Measured in threads per inch
• Metric
• Measured by the distance in mm between the treads
  

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Measuring

• Bolt Size Major Diameter
• Bolt head size Distance between the flats of
  the hexagon

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Measuring

• Bolt length the distance from the base of the
  head to the end of the thread
• Thread pitch Threads per inch Distance
  between threads

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Grade

• Tensile strength (pulling strength)
• Amount of PSI the bolt can handle
• Only accurate for bolts with a 1 inch diameter

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Grade

• Grade stamped on top
• Imperial grade number of lines Two
• Metric Grade is printed
• 5D, 8G, 10K, 12K.

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Under load

• When a bolt goes past its load capacity it
  reaches its elastic limit
• After elastic limit the bolt stretches and looses
  strength

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Torque Specs

• All bolts on a vehicle have a special
  specification that they have to be tightened too.
  
• Always look this up in the manual before
  tightening any thing

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Flat Washers

• Used to make larger bearing surfaces for nuts to
  ride on
• Stops nuts and bolts from becoming imbedded in
  soft materials

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Lock Washers

• Prevents fastener from loosening
• Made from spring steel
• Split and bent, cuts in to base material and
  fastener

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Multiple Tooth Washer

• Solid piece
• Has twisted teeth that dig in to fastener and
  base metal

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Pins

• Retains parts in a fixed position
• Used for alignment

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Cotter Pins

• Used to hold nuts in position
• Specifically Castle nuts

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Snap Ring

• Clips in to groves to retain parts
• Groves can either be external or internal

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Keys

• Used to fix gears and pulleys to shafts
• Cut in gear or pulley called the key seat
• Cut in shaft called the key way

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Adhesives

• Liquid or semi-liquid
• Prevents loosening
• Only one drip
• Range from light to strong

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Sealants

• Resistance from the elements
• Oil, water, gas, grease, and salt