3. Basic Applications of Threads
Basic Applications of Threads
How are threads used?
How are threads used?
1.
1.Hold parts together
Hold parts together
2.
2.Adjust parts
Adjust parts
3.
3.Transmit power
Transmit power
4. All screw threads wind around a shaft in a
curve called a HELIX
•the string
represents the
general form of a
HELIX .
•Another example
of a HELIX curve is
a coiled spring
5. Tapping A Small Hole
Tap Tool - is a small
fluted cutting tool with
cutting teeth shaped to
form small internal
threads.
6. Cutting Large Threads
External threads are formed
by cutting helical grooves
around the shaft on a lathe.
The Lathe can
produce large
internal threads by
using a boring tool
8. Thread Forms
• Sharp V or Sellers
Thread
• First U.S. Standard
Thread
• Now used on brass
pipe work
9. Thread Form
Unified Thread
• Adopted by the U.S.,
British, and Canada
after World War II as
an ANSI standard.
• Mainly used for
fastening and
adjusting
10. Thread Form
• Metric Thread
• Adopted in 1946 by
the International
Organization for
Standardization (ISO)
11. Thread Form
Square Thread
• Theoretically the ideal
thread for power
transmission
• Tough to cut the
threads because of
the 90° angles
12. Thread Forms
ACME Thread
• Modification of the
square thread
• Stronger and
easier to cut than
the square thread
• Also used to
transmit power.
• Better know as a
worm thread.
13. Thread Forms
• Whitworth Thread
• First standard in
England
• Has been replaced by
the Unified thread
14. Thread Forms
• Knuckle Thread
• Typically rolled from
sheet metal
• Sometimes is formed
by casting
• Used in light bulbs,
sockets, and jar &
bottle tops
15. Thread Forms
• Buttress Thread
• Designed to transmit
power in one direction
• Used on large guns,
screw jacks, and
Bumper Jacks.
25. Annotation For Metric Threads
M10 X 1.25
Metric thread
Major diameter
Separation
Thread pitch
26. Course (General Purpose) Fine
Nominal Size &
Pitch
Tap Drill
Diameter
Nominal Size &
Pitch
Tap Drill
Diameter
M10 X 1.5 8.5 M10 X 1.25 8.75
M12 X 1.75 10.30 M12 X 1.25 10.5
M20 X 2.5 17.5 M20 X 1.5 18.5
Example Of A Metric Screw Thread Table
27. Left Hand Threads Advances Counterclockwise
Right Hand Threads Advances Clockwise
28. Other Types Of Threaded
Other Types Of Threaded
Fasteners
Fasteners
Bolt
Bolt &
& Nut
Nut
Cap Screws
Cap Screws
Machine Screws
Machine Screws
Set Screws
Set Screws
Wood Screws
Wood Screws
29. CAP SCREWS
Used to fasten parts together.
Have a naturally bright finish to
match the machined part.
Chamfer to the depth of the first
thread
30. Cap Screw Types
(a) Round, (b) Pan, (c) Oval, (d) Hex, (e) Socket,
(f) Flat, and (g) Phillips
32. Cap Screws & Bolts
• What is the difference
between a cap screw
and a bolt?
• Cap screws fasten
into a threaded blind
hole.
• Bolts are usually
accompany by a Nut
to fasten parts
together.
33. Hex Socket Cap Screw
Is BEST used with
a counterbored
hole
35. Set Screws
• There are generally two
types: square-head and
headless.
• Because of safety issues
the headless setscrew
would be best for rotating
parts.
36. Set Screw
Used to hold
the collar to
the shaft
This type of set screw would
be a safety issue if the
assembly had a rotating
motion.
37. Fasteners For Wood
• Wood Screws – create their own thread
when you drive them into soft woods
such as pine and spruce.
– Cone shaped shafts for easy entry into
the wood.
– Hard woods, such as maple or oak,
may require drilling a pilot hole.
– Wood screws have flat, round, or oval
heads with slotted or Phillips head
configurations.
40. Keys
Keys
Are used to prevent relative
Are used to prevent relative
movement between, wheels,
movement between, wheels,
pulleys, gears, cranks, and
pulleys, gears, cranks, and
similar parts to a shaft.
similar parts to a shaft.
42. Square Key – Design is used for heavy-
duty functions. Sometimes referred to as a
flat key.
43. Gib Head Key – It is exactly the same as
the square key except that it has a gib head,
which provides for easy removal.
44. Pratt & Whitney Key – is rectangle in
shape with semi-cylindrical ends.
45. Woodruff Key –
is semicircular in
shape and is often
used in machine-tool
work. The bottom of
the key fits into a
semicircular key slot
cut with a Woodruff
cutter and the top into
a rectangular slot.
47. Types of Pins
Clevis pin
Straight pin
Taper pin
Cotter pin
Use pins when the
need for disassembly
of parts by hand or
tools.
Use where appearance is
not critical (pins need to
protrude).
48. 1. Rivets – are regarded as permanent fasteners.
2. Generally used to hold sheet metal or rolled
steel shapes together.
3. The shaft of the rivet is inserted into the
aligned holes of the matting parts and then
formed to create a head on the opposite end of
the shaft, establishing a permanent assembly.
Rivets
