Electromechanical Components Midterm
Petroleum is formed by an evolutionary process that takes many millions of year
true
How is an isometric sketch drawn
2D representation of something 3D
What two types of babbitt metals work best for plain bearing modes
Tin base and lead base babbitt metals are the best metals for plain bearing modes
Why is the frame of the outside micrometer U-shaped
To allow the anvil and spindle to fit around the workplace
What does proper handling, calibration, and storage of precision tool measuring instrument insure
accuracy and precision
A 40 weight oil is thicker than a 10 weight oil
true
Animal and vegetable oils are used mostly in the food industry
true
Animal and vegetable oils contain fatty acids
true
As temperature increases, grease becomes softer
true
Friction occurs when an object in contact with another object tries to move
true
Gas lubricants are commonly used for low friction, high speed, high technology applications
true
Plain bearings may support radial and axial loads
true
Precision measuring instruments handling requires proper cleaning and lubrication of the instrument before and after each use
true
Sealed bearings should never be relubricated on a regularly scheduled basis
true
Shear stress is stress in which the material in one side of a surface pushes on the material on the other side of the surface with the force parallel to the surface
true
Solid lubricants such as graphite shear easily between sliding surfaces
true
Some greases exhibit a dropping point
true
Synthetic lubricants are generally higher priced than petroleum lubricants
true
The flow rate is the most important property of a lubricant
true
The grease used in a centralized system should be one grade softer than is otherwise required
true
Under basic conditions, as the temperature of oils increase, their viscosity also decreases
true
Walking requires friction between the feet and floor in order to move
true
Water that mixes with lubricants decreases the effectiveness of the lubricant
true
Two examples of when fretting corrosion becomes harmful
1. When the oxidation breaks down supporting wall surfaces to create looseness. 2. as its oxidation particles mix with and break down the bearing lubricant
Identify and define the four systems associated with oil application
1. gravity 2. submersion 3. splash 4. wick 5. closed loop pressurized system
Two most commonly used system of measurement
1. metric 2. english
List three ways lubricant helps ensure smooth and safe operation of tools and machines
1. reduce component wear 2. dissipate heat 3. prevent corrosion
What is the difference between a drawing and a sketch
A drawing has exact measurements. A sketch is an idea
Define radial load and axial load, and identify an example of a combined radial and axial load
A radial load is a load in which the applied force is perpendicular to the access of rotation. An axial load is a load in which the applied force is parallel to the axis of rotation. Radial and axial loads occur when a combination of the two loads are present. An example of a radial and an axial load is present in the shaft of a fan blade since it is supported horizontally and is pilled of pushed.
What are the different scales commonly used and how are they selected for a print
A scale is a numeric mappings from the drawing to reality. There is architectural scales and engineer scales
Vernier scale
A short auxiliary scale placed along the main scale of a measuring instrument to provide accurate fractional readings
Ray
A straight line or lines intersecting a point of an angle.
Why are rolling contact bearings referred to as anti friction bearings
Because they are designed to roll on a film of lubricant which separates the metal components
Define digital micrometer and describe two ways in which it differs from a standard micrometer
Digital micrometer is is a micrometer with a digital electronic indicating gauge The difference is that it is battery powered with a digital display. They are also easier and quicker to read
What info is commonly included in these drawings
How items look like and it fits in the system
Explain the difference between the lower level explosive limit (LEL) and upper explosive unit (UEL)
LEL concentration below the limit are too lean to burn. UEL concentrations above this limit are too rich to burn
What are the common types of drawings used for machinists
Orthgraphic
What are common types of drawings used by industrial and mechanical technicians
Pictorial, application, location, assembly, instructional, section
What are the two main causes of slips and falls in the work place
Poor house keeping inappropriate footwear
List three factors that the accuracy of a micrometer measurement is dependent on
Quality, care, and skill of a person
Why is it important to make sketches that are correctly proportioned
So that the person reading the sketch does not get confused
what is the minimum working height that requires the use of a personal fall- arrest system
Ten feet
Precision
The level of accuracy or mechanical exactness
What is the main difference between the graduations on a depth micrometer level barrel scale when an outside micrometer is properly calibrated
They are reversed
What is a liquid lubricant used for and what are three reasons it is the preferred lubricant and what are three reasons why it is the prefered lubricant
They are used for heat removal or as a sealer. They are preferred because 1. their reliability 2. their versatility 3. their flexibility
List two advantages of using synthetic fluid as opposed to petroleum based lubricant
They increase efficiency and performance but they are are expensive
Which way should bearings that can be mounted in either direction face and why
They should be mounted with the part number facing out for ease of future identification
A __________ is a permissible range of variation in a dimension or given value
Tolerance
Angle
a geometric figure formed by two lines extending from same point
Why is mixing different manufacturers bearings typically not recommended
because each angular contact ball bearing has a ground finish on the back on the back and face
Why is it important to never strike a bearing directly with a hammer during bearing removals
because these are both hardened metals that can shatter when struck together
Explain why oil must be replenished in order to ensure all parts within a mechanical apparatus receive the proper amount of lubrication
burning, leaning
What info is commonly found in a title block
company, legend, revision number, title, and name
Why are specifications included in a set of prints
dimensions, legends, and bill of materials
When do the effects of boundary lubrication mostly occurs
during stopping, starting, and periods of severe operations
Describe one negative effect associated with exposing precision measuring instruments to temperature extremes
encourage oxidation therefore rust
Needle bearings are designed primarily for relatively low radial loads
false
Prelubricated bearings may be heated for installation
false
List eight different bearing precautions that should be taken when mounting bearings
file:///C:/Users/miche/Desktop/Important%20Stuff/Chapter%209%20review%20answers.pdf
How does thrust damage on ball bearings appear
on marks on the shoulder or upper portion of the inner and outer race and will be anywhere from a slight discoloration to heavy galling
Identify why graphite is useful as a solid lubricant and explain when it is not useful when humidity is absent
slides easily adhere to surface you want to lubricate. It needs water to function though
A vernier scale is a short auxiliary scale placed along the main scale of an instrument to provide accurate fractional readings
true
An accident victim needs to provide consent before care is administered
true
An inside micrometer is a micrometer used to measure linear dimensions between two inside points or parallel surfaces
true
An outside micrometer is a micrometer used for measuring outside diameters and thicknesses of parts
true
Angles are measured in degrees and radians
true
As the temperature of steel increases, it discolors, turning from silver to blue to black
true
Babbitt metals are the best metals for plain bearing loads
true
Balled bearings are installed with one ring being a press fit and the other ring a push fit
true
Basic calibration of a depth micrometer requires that the measurement or rod extension start at zero
true
Digital calipers are more precise and easier to read then vernier scale or dial calipers but require a DC power source for operation
true
First aid is help for a victim before professional medical help arrives
true
Never apply pressure on the outer ring if the inner ring is press fit and never apply pressure on the inner ring if the outer ring is press fit
true
Precision test instruments will give faulty readings because of an expansion or contraction of the test instrument caused by temperature extremes
true
Pull tools rather than pushing them for greater control and balance
true
Roller contact bearings include ball roller and needle bearings
true
Safety shoes with reinforced steel provides protection against injuries caused by compression and impact
true
Solid or caked lubricant is a sign that bearings have overheated
true
The PPE selected must ensure a level of protection greater than the minimum level required to protect a technician from the hazard
true
Explain how a respirator is selected
A respirator is selected based on the type of material or chemical hazard to which a technician is exposed
List three examples of lubricant additives and explain how each one protects a machine from harm
Additives include oxidation inhibitors (to provide long bearing or gear life), rust inhibitors (to prevent rust), fatty materials (to improve film strength)
__________ action is the action by which the surface of a liquid is elevated on a material due to its relative molecular attraction
Capillary
What do dark discolored metals, rusting surfaces, and split and split or fractured rings indicate about failed or fail bearings
Close examination of a failed bearing often provide evidence to the cause of failure.
Explain how brinell hardness test works
It measures the hardened the metals by hydraulically pressing a hardened steel ball into the metal to be tested and then measuring the area of indentation
Tapered bore bearing
Its a bearing that uniformly increases or decreases from one face to the opposite face
Semisolid lubricant
Liquid with metal based soap
Describe the advantages of the base design on a depth micrometer
The base design allows the micrometer to be positioned on the work piece perpendicular to the surface from which the depth is measured
Accuracy
The degree to which a measurement conforms to a specific standard
What does the viscosity index scale show
The magnitude of viscosity changes in lubrication oils with changes in temperature
Vertex
The point of an intersection of the sides of an angle
Plain bearing
a bearing in which the shaft turns and is lubricated by a sleeve
Liquid lubricants include__________
animal and vegetable oils petroleum fluids synthetic fluids
Bearing installation is generally more difficult than bearing removal
false
Doubling the load on a bearing increases its service life by 6 to 8 times
false
How is an orthographic sketch drawn
front, side, and back view
What is the most common work related disease
going deaf
List three types of measurements calipers are used to take on components
inside, outside, length
During startup of a machine, oil ___________
is cool does not flow easily
Explain how an increase in temperature affects grease consistency
it flows faster and if too hot the liquid and solid would separate
What is a good Samaritan law
it gives legal protection to individuals who provide emergency care to accident victims
Describe the proper way to adjust precision measuring instrument to the ambient temperature before use
let tool sit out for about thirty minutes so it can be same temperature of ambiance
What does the practice of wear particles analysis focus on
metal shaving
Why are two main causes of injuries in the work place
not paying attention or taking chances
How are curved parts dimensioned
radius or diameter
Lubricants are used to _________
reduce friction prevent wear prevent corrosion
Why is selecting the proper tolerances important
so parts will fit properly
What does SAE viscosity ratings based on
the ability to flow
Spalling
the flaking away of metal pieces due to metal fatigue
Fretting corrosion
the rusty appearance that results when two metals in contact are vibrated, rubbing loose minute metal particles that become oxidized
Describe the relationship between a thimble scale and barrel scale when an outside micrometer is properly calibrated
the two zeroes should line up
Why are bearings designed for thrust loads installed in only one direction
to prevent the load from separating
A better finish on a bearing produces less friction
true
A code is a regulation or minimum requirement
true
A machine should never be grounded by connecting a wire from the machine to a gas or oil pipe
true
A machinist steel protractor is a tool used to measure or mark angle measurements on rigid pliable workpieces
true
Graphite has low sheering forces
true
Greater force is required to move a body from static condition than is required to keep it in a kinetic condition
true
If quart or more of blood is lost quickly , shock and or death is possible
true
Individuals suffering from heat exhaustion may feel disoriented, feel dizzy, feel fatigued, have a headache, or have flu-like symptoms
true
Lubricating oil is given an SAE viscosity rating based on its ability to flow at a specific temperature
true
Lubrication contamination is the main cause of mechanical system failure
true
Lubrication generally involves coating surfaces with a material that has lower coefficient of friction than the original surface
true
Materials used in whole-body PPE include rubber, leather, synthetic, and plastic
true
More bearings are destroyed damaged or abused during the installation stage than from malfunction during their life expectancy
true
Needle bearings are generally press fits
true
Oil that is contaminated with water has a milky appearance
true
Over greasing leads to overheating , aerating, and churning of the grease , resulting in early bearing failure
true
Petroleum is composed of 85% carbon and 12% hydrogen, with a small amount of other elements
true
False Brinell damage is a bearing damage caused by forces passing from one ring to the other through the balls or roller
true