Threaded Fasteners

1
Threaded Fasteners

• Simplified Thread Representation
• Two types
• Permanent Rivets and welds.
• Removable Bolts, screws, nuts, keys, rings, etc.

2
Threaded Fasteners

• Simplified Thread Representation
• Screw Threads
• Thread The sectional shape of the thread
  generated about the cylinder in the form of a
  helix.

3
Threaded Fasteners

• Simplified Thread Representation
• Screw Threads
• Pitch The distance from a point on the thread
  form to the corresponding point on the next form,
  measured parallel to the axis. PPitch

4
Threaded Fasteners
Thread Representation Inch Threads
5
Threaded Fasteners
Thread Representation Inch Threads

• ¼-20UNC
• 20 represents the number of threads per inch.

6
Threaded Fasteners
Thread Representation Inch Threads

• ¼-20UNC
• 20 represents the number of threads per inch.

7
Threaded Fasteners
Thread Representation Inch Threads

• 3/8-16UNC
• 16 represents the number of threads per inch.

8
Threaded Fasteners
Thread Representation Inch Threads

• 3/8-16UNC
• 16 represents the number of threads per inch.

9
Threaded Fasteners

• Simplified Thread Representation
• Screw Threads
• Lead The distance the threaded part would move
  parallel to the axis during one complete
  rotation.

10
Threaded Fasteners
Thread Representation Single threads LEADPITCH
11
Threaded Fasteners
Thread Representation Double threads
LEAD2(PITCH).
12
Threaded Fasteners

• Simplified Thread Representation
• Screw Threads
• Forms The sectional shape of the thread.
• ISO Metric
• ACME

13
Threaded Fasteners

• Simplified Thread Representation
• Screw Threads
• Forms The sectional shape of the thread.
• Square
• United National

14
Threaded Fasteners

• Thread Representation
• Simplified Draw chamfers at the end of the
  bolt, then draw the hidden lines from the
  chamfers to the end of the threads.

15
Threaded Fasteners

• Thread Representation
• Detailed Used for larger parts, usually above
  1

16
Threaded Fasteners

• Thread Representation
• Schematic Not used today.

17
Threaded Fasteners

• Thread Representation
• Right Hand Advances as it turns clockwise into
  the mating feature.
• Left Hand Advances as it turns
  counter-clockwise into the mating feature.

18
Threaded Fasteners

• Thread Representation
• Crest (external threads.) is the point on the
  screw thread at the greatest distance from the
  axis.

19
Threaded Fasteners

• Thread Representation
• Crest (internal threads.) is the point on the
  screw thread nearest the axis.

20
Threaded Fasteners

• Thread Representation
• Root (external threads.) is the point on the
  screw thread nearest the axis.

21
Threaded Fasteners

• Thread Representation
• Root (internal threads.) is the point on the
  screw thread at the greatest distance from the
  axis.

22
Threaded Fasteners

• Thread Representation
• Depth of Thread The radial distance (measured
  normal to the axis) between the crest and root of
  a screw thread.

23
Threaded Fasteners

• Thread Representation
• Major Diameter The largest diameter on a screw
  thread.

24
Threaded Fasteners

• Thread Representation
• Minor Diameter The smallest diameter on a screw
  thread.

25
Threaded Fasteners

• Thread Representation
• Pitch Diameter The diameter of an imaginary
  concentric cylinder cutting the threads so that
  the width of the cut thread metal and the width
  of the separating space are equal.

26
Threaded Fasteners

• Thread Representation
• Simplified

27
Threaded Fasteners

• Thread Representation
• Simplified

28
Threaded Fasteners

• Thread Representation
• Simplified

29
Threaded Fasteners

• Thread Representation
• Simplified

30
Threaded Fasteners

• Thread Representation
• Simplified

31
Threaded Fasteners

• Thread Representation
• Series The term used to designate the pitch of
  the threads. Coarse, Fine, or Extra Fine
• Course Used for most general-purpose screw
  threads. Their strength is the greatest.
• Fine Used where special holding conditions
  require a finer thread such as in automotive and
  aircraft parts.
• Extra-Fine Used for highly stressed
  applications where engagement is limited. Thin
  walled parts.

32
Threaded Fasteners

• Thread Representation
• Class of Fit Describes the accuracy and
  precision used to manufacture the threads.
• ¼-20UNC-2A
• Class 1 Loosest Fit
• Class 2 Medium Fit
• Class 3 Closest Fit
• A External Threads
• B Internal Threads

33
Threaded Fasteners

• Thread Representation
• Unified Threads Specified by diameter, inverse
  of pitch, and series.
• ¼-20UNC-2B
• 1/4 Nominal Thread Diameter
• 20 Number of thread per inch.
• UN Unified National Threads
• C Coarse series.
• 2 Class of fit
• B Internal

34
Threaded Fasteners

• Thread Representation
• Call-out

35
Threaded Fasteners

• Thread Representation
• Simplified
• (See page A-6
• Table 8 for thread
• and tap drill
• information)

36
Threaded Fasteners

• Thread Representation
• Metric

See next slide
37
Threaded Fasteners

• Thread Representation
• Metric
• M Metric thread
• 12 Nominal diameter in mm
• 1.25 Pitch

38
Threaded Fasteners

• Thread Representation
• Metric
• The pitch can be omitted for coarse series
  threads.

39
Threaded Fasteners

• Thread Representation
• Metric
• The fit is listed as a pitch and crest diameter
  tolerance.

40
Threaded Fasteners

• Machine Screws
• Smaller fasteners, available in fine or coarse
  threads.
• Cap Screws
• A fastener that joins two or more parts by
  passing through a clearance hole and screws into
  the tapped hole. Sizes start at .25

41
Threaded Fasteners

• Bolts
• A fastener that passes through clearance holes
  and is assembled with a nut.
• Studs
• Shafts that are threaded on both ends.

42
Threaded Fasteners

• Head Configurations
• Hex and Square
• Pan
• Binding
• Washer (Flanged)
• Oval
• Flat

43
Threaded Fasteners

• Head Configurations
• Fillister
• Truss
• 12-Point

44
Threaded Fasteners

• Point Styles
• Cup
• Flat
• Cone

45
Threaded Fasteners

• Point Styles
• Half Dog
• Oval

46
Threaded Fasteners

• Thread Representation
• Page
• A-2 Decimal equivalents
• A-5 Number and letter-size drills
• A-6 Inch Threads
• A-7 Metric Threads Machine and Cap Screw sizes
• A-9 Hex Nuts