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

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 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 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

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

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

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

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

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

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

A vernier scale is a short auxiliary scale placed along the main scale of an instrument to provide accurate fractional readings

true

Angles are measured in degrees and radians

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

__________ 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.

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

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

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

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

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

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

List two advantages of using synthetic fluid as opposed to petroleum based lubricant

They increase efficiency and performance but they are are expensive

Why is the frame of the outside micrometer U-shaped

To allow the anvil and spindle to fit around the workplace

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

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 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

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

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

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

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.

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.

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)

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

When do the effects of boundary lubrication mostly occurs

during stopping, starting, and periods of severe operations

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

Prelubricated bearings may be heated for installation

false