School of Technology

TECH 13580 - Engineering Graphics I

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Fasteners  

• Welding - Welding symbols
• Rivets
• Nails
• Adhesives
• Joinery

• Screws - wood & metal
  • Round & Flat head wood screws - whole # diameter (#6,#8,#10,#12,etc.)
  • Pan head sheet metal screws
• Bolts (includes screw & nut)
  • Hexagon head & hexagon slotted head
  • Square head (also called machine bolt)
  • Round head square neck (commonly called carriage bolt)
  • Countersunk square neck
  • Step bolt (for applications dealing with rust to provide larger bearing surface)
  • Round head ribbed neck (ribs to secure bolt when unthreading)
  • Round head fin neck
• Cap screws (high quality steel, nut not included, threads to tapped hole, fraction diameter)
  • Flat head (requires countersunk hole, length = overall length, 59° thread angle)
  • Round head (length = underside of head to end)
  • Hex socket head (uses Allen head, length = underside of head to end)
  • Fillister head (straight sides, used in electronic chassis, length = underside of head to end)
  • Hex head (most popular, length = underside of head to end)
• Machine screws (like cap screws, except smaller diameter sized by whole #, example: 10-24 = #10 diameter with 24 threads per inch)
• Set screws (to attach pulley, etc. to a shaft)
  • Square head (external wrenching, tight, but dangerous)
  • Slotted head (tighten with screwdriver)
  • Hex socket head (tighten with Allen wrench)
  • Fluted socket head (tighten with special wrench)
  • Flat point (end contacting shaft)
  • Oval point
  • Full dog point (fits in milled hole in shaft)
  • Half dog point (like full dog, but not as long)
  • Cone point (self guiding to drilled shaft hole)

• Stud (shaft with both ends threaded, no head, one end has interference fit, used in cast iron and aluminum engine blocks, whereby stud remains in place with nut removed to disassemble cylinder head from block)

• Thread form (see "Thread forms")
• Thread angle
• Pitch (from like point to like point, i.e. crest to crest)
• Major diameter (across from crest to crest)
• Minor diameter (from root to root)

• Pitch diameter (an imaginary cylinder passing through threads - nut to screw contact)
• Crest (uppermost feature of a thread)
• Root (lowest feature of a thread)
• Lead (distance nut travels in one revolution)
  • Single lead (one starting point of thread path)
  • Double lead (two starting points 180° apart)
  • Triple lead (three starting points 120° apart)
  • Quadruple (four starting points 90° apart)

• Sharp V (60° thread angle, pointed crest, old Sellers thread)
• Unified National (UN) = American National (the thread found commonly used, found in hardware stores, combines features of Sharp V and Whitworth)
• Square (used when strength required, found on lead screw of lathe)
• Acme (used when strength required, truck tire jack, etc.)
• Buttress (used on naval guns, nearly vertical side = strength)
• Knuckle (used on light bulbs, etc.)
• Whitworth (an old English thread design featuring rounded root & crest)

• Helix (accurate and true spiral shape, too time consuming to draw)
• Detailed = Semi-conventional (uses straight lines to connect crests and roots, time consuming, used when diameter on drawing is 1"or larger)
• Schematic (long lines represent major diameter & shorter heavy black lines represent minor diameter, 1/16" space between lines regardless of threads per inch)
• Simplified (uses hidden lines to represent minor diameter, saves time = popular)

• Leader touches thread
• Major diameter
• Threads per inch (TPI) found is table on back of text, determined by series (1/2" coarse=13 TPI & 1/2" fine series has 20 TPI)
• Thread form (UN or Acme or square or knuckle, etc.) = thread profile
• Thread series (coarse, fine, or extra fine)
• Class of fit (#1=loose, #2 =common, #3=tight fit between screw and nut, #4=extremely tight fit, unable to tighten by fingers)
• Kind of thread (A=external & B=internal)
• Thread direction (right-handed is implied "Righty tighty, lefty loosy", LH = left- handed LH indicates tighten via counter-clockwise, LH used on saw arbors for safety)
• Lead DBL = double, etc. single lead is otherwise implied and not noted