Chapter 3, Summary Flashcards
What kinds of conditions are fasteners that are used in assembly of small gasoline engines, exposed to?
Heating and
cooling,
cyclic loading,
tensile loads,
shear loads,
corrosion, and
vibration during engine operation.
When disassembling an engine, why is it vital to note the location of all parts, fasteners, and washers
so they can be replaced in proper location
Damaged fasteners should be repalaced with new ones.
Lightly rusted fasteners may be cleaned and examined for reuse.
[______] are threaded fasteners that hold parts together by squeezing them between the [____] head on one end and a nut on the other
Bolts
Q: Why is a lock washer often placed between the face of a nut and the part surface?
A: To prevent loosening caused by vibration.
Nuts vary in shape and size depending on what?
Their intended function.
The most common nuts are:
Plain hexagon nuts
Name 5 other types of nuts
wing nuts,
castle nuts,
acorn nuts,
jam nuts, and
various self locking nuts
Bolt terminology includes:
Major diameter,
head size,
length,
and thread pitch.
Bolt grades are related to :
The minimum tensile strength of the bolt.
Bolt heads are marked with symbols to identify what?
The grade of the bolt.
Thread types of signifigance for small gas engines are :
Unified National Coarse ( UNC)
Unified National Fine ( UNF)
Metric (M)
Threads of a bolt or screw must be the same as :
The mating thread in the hole or nut.
Threads are identified by what?
A thread designation.
2 examples of thread designatiins are:
1/2-13 UNC-2A For standard threads,
and M10 ×1.5×25 for metric threads.
How do screws hold parts together?
By passing through one part and threading into another.
Bolts, nuts and screws on engines should be tightened according to specifications, using what?
A torque wrench.
How can threads be repaired?
by chasing them with a threading tap for holes -or-
a threading die for bolts and screws
When tapping new threads, how di you determine the proper size of the hole to be drilled?
From a tap drill chart.
Flat washers are used to do what?
Provide a bearing surface for bolt and screw heads and nuts.
Various types of lock washers do what?
Prevent loosening of bolts and screws
What type of pins are used to secure castle nuts and clevis pins?
Cotter pins
[—-] and [—-] are used for alignment of parts and should fit quite snugly.
Dowel pins and straight pins
How are grooved pins placed into what kind of holes?
They are driven into interference fit holes.
The [—–] are cut into the walss of the hole to secure the pin.
Grooves
what pins have a taper along their entire length.
Taper Pins
Taper pins are used for what purpose?
Fastening pulleys and gears to shafts to prevent slipping around the shaft.
[———-] are circular spring steel fasteners that fit into a groove around a shaft or in a hole.
Retaining rings
What kind of tool is used to install and remove retaining rings?
A special plier-like tool
[—-] are used on shafts that havd a gear, pulley or sleeve that fits and rotates with the shaft
Keys
Keys rest in what ?
the keyseat, and keyway.
Many types of [—-] and [—-] are used on engines and implements.
Adhesives and sealants.
Thread locking compounds are used for what purpose?
Preventing threaded fasteners from loosening due to vibration.
Some [—————] are used to prevent leakage between parts.
Liquid sealants.
What is important to do when using liquid sealants?
Use the correct onr as specified by the manufacturer.
What are Antiseize compounds ?
Lubricants that prevent parts from locking together.
What are used to seal between engine parts to prevent leakage of engine oil, coolant, compression, and vacuum?
Gaskets
What is important to consider when replacing a gasket?
Selecting the cirrect material, shape, and thickness.
The unthreaded part of a bolt or screw is called the:
Shank
The helical portion of a bolt or screw is called the:
Thread
A type of hardened screw that makes its own threads, usually found in sheet metal, is a[——] screw
Self tapping
(?)The term bolt implies the use of a [—–]
Nut?
Jam nuts are usually used with [—-] nuts.
Hexagon
The proper thread notation fir a 14 millimeter thread with a 1.5 millimeter pitch on a screw that is 40 millimeters long is[——————-]
[B] M-14 × 1.5 × 40
The proccess of cutting new threads into a hole is called :
A: Tapping
T or F: For cutting threads in a through hole, the proper tap to use would be a taper tap?
True
The cutting tool used to cut external tgreads is called A:
Die / inside a die stock handle.
To provide a wider bearing surface for a bolt head or nut, a [——] washer should be used.
Flat
(?) [True or False]
If a 1/8” rolled pin is to be used in a shaft, the correct drill size to use for drilling the hole for this pin should be 3/16” diameter.
[?] False
What type of fasteners are used to lock castle nuts?
A: Cotter pins
[True or False] Retaining rings are made of spring steel.
True
[———-] can be applied to the threads of nuts, bolts, or screws to prevent them from loosening during service.
B: Thread adhesive
Gaskets are used between engine parts to seal and prevent leakage of all the following except:[—–]
D: Sealant
How do you use a screw extractor to remove a fastener that has broken off below the surface it is threaded into:
Drill a hole approximately one half of the broken fasteners diameter at top center of it. Then tap the extractor into the hole using a hammer; The spirals on the extractor cause it to wedge tightly into the broken fastener. Use a wrench or socket to grip the extractor and back the broken fastener out if the hole.
If a hole goes all the way through it is called:
A through hole.
Holes that do not go all the way through the matrerial are called:
Blind holes
Answer the folowing questions about the thread notation given below:
A: 3/8-16 UNC 1A
B: The major diameter of the thread is: (3/8”)
C: How many threads per lineal inch are there?: (16)
D: Is the thread coarse or fine?: (Coarse)
E: Is the thread internal or external?:(External)
F: Is the thread a Loose, average, or close fit? ( Loose)
When tightening bolts on an engine head, why is it important to use a crisscross pattern unless a different pattern is specified by the manufacturer?
This procedure produces even gasket compression and sealing, and prevents possible warping of parts.
When reassembling an engine, it is recommended that cotter pins be replaced rather than reused. Why should you never reuse a cotter pin?
Because it will have weakened from being bent, and might possibly break.
Form- in - place sealants can be used in place of coventional gaskets. What are the advantages and disadvantages of using a sealant instead of a conventional gasket?
Advantages: lessens need to stock various sizes and shapes of gaskets.Increases seal strength. Improved reliabilty. Reduced cost, easier application.
Disadvantages: Anerobic sealants not good for high heat applications above 200°C.
Silicone sealants can have Poor resistance to fuel and aromatic solvents. Not recommended for high pressure applications.
UNC
Unified National Coarse
UNF
Unified National Fine
