Page 86 - Analysis and Design of Machine Elements

Analysis and Design of Machine Elements
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3.3 Threaded Fastening Methods
3.3.1 Types of Threaded Fastening Methods
Threaded fastenings are the basic assembly method in the design and construction of
machines. Threaded fasteners join the matching external and internal threads together
by the following typical methods.

1. Bolted joints
A bolted joint is designed to let a bolt to pass through holes in mating members
and secured by tightening a nut from the opposite end of the bolt [2]. Both ordi-
nary bolted joints (Figure 3.3a) and precision bolted joints (Figure 3.3b) are available.
Ordinary bolted joints have bolt shanks inserted in the holes with a clearance, while
precision bolted joints have bolt shanks fitting into reamed holes without appreciable
clearance. Both of them are applied to join relative thin members by using thorough
holes.
2. Stud joints
A stud is a stationary bolt attached permanently to one of the members to be joined.
The mating member is then placed over the stud and a nut is tightened to clamp
the members together, as indicated in Figure 3.3c. A stud joint applies when one
of jointed components is too thick to drill a body size hole. The joint can be disas-
sembled frequently by removing the nut and washer, without damaging the threaded
member.

3. Cap screw joints
A cap screw fastening is designed to let a cap screw to insert through a hole in one
member to be joined and into a threaded hole in the mating member [2], as shown in
Figure 3.3d. The threaded hole may be formed by tapping or by the cap screw itself.
It applies when one of jointed components is too thick to drill a body size hole or the
spaceistoo smalltomountanut. Such joints cannotbedisassembledfrequently.
4. Setscrew joints
A headless setscrew is designed to be inserted into a tapped hole to bear directly
on the mating element, as shown in Figure 3.3e. Setscrews depend on compression
to develop clamping force to lock components into place. They are inexpensive and
adequate for light service. However, they should not be used in vibration applications
where loosening would impose a safety hazard.

(a) (b) (c) (d) (e)
Figure 3.3 Types of threaded fastening methods.