Download 3.4 Thread classifications Threads are classified according to four

3.4 Thread classifications
Threads are classified according to four
factors:
1. Purpose
We distinguish between fastening threads
and motion-transmitting threads.
Fastening thread
E Fastening threads
are generally single-threaded V-shaped
threads with an included thread angle
of 60° (55°) and a maximum lead angle
of 5°.
The frictional forces generated by fastening threads must be high enough to
prevent the components from loosening by themselves.
If a fastening thread fulfils this condition, it is self-locking.
Motion-transmitting thread
E Motion-transmitting threads
are used to convert rotational motion
into linear motion or vice versa.
Motion-transmitting threads have different profiles depending on the load
and can be multi-threaded.
9
4.1.3 Taps for different materials
Tap for steel
The cutting geometry depends on the
materials to be cut.
Tap for steel
α
E α – clearance angle (only on starting
taper)
β
E β – wedge angle
E γ – rake angle approx. 5˚–10˚
γ
Chip space
Tap for non-ferrous metals
Tap for non-ferrous metals
Taps for non-ferrous metals have larger
rake angles (γ) and wider flutes.
The clearance angle (α) can go back to 0.
The chips that are created during thread
cutting are collected and carried away in
the chip spaces.
γ
β
Chip space
α = 0˚
Guide values for rake angles on taps
Material
Rake angle γ
Brass, bronze,
hard cast iron,
tough steel
0°. . . . . . .5°
Steel up to 700 N/mm2
strength, cast iron
up to 200 HB
5° . . . . . 10°
Long-chipping
light metals
20˚ . . . . 30˚
21
4.7 Exercises with solutions
Angular functions in a right-angled triangle
Angular functions are geometric relations
se
enu
t
o
Hyp
α
Adjacent side
Opposite side
α = known angle
Hypotenuse = side located opposite
the right angle.
Adjacent side = side located adjacent to
the known angle.
Opposite side = side located opposite the
known angle.
Angular functions in a right-angled triangle
sin α =
Opposite side
Hypotenuse
cos α =
Opposite side
Adjacent side
Adjacent side
Hypotenuse
ctg α =
Adjacent side
1
=
Opposite side tan α
cos α =
Exercise 1
Enter the function values of the following angles.
Angle
Function value
sin α
α
cos α
tan α
ctg α
10°
20° 30'
35.6°
Exercise 2
Identify the angles α and enter the results in degrees and minutes.
Function value
Angle α
sin α = 0.1564
cos α = 0.8732
tan α = 1.3500
ctg α = 0.3915
35