dml midterm practice

Which of the following is not a common component of an engine lathe:
A. headstock
B. cross slide
C. tool post
D. tailstock
E. ram

E. ram

What rotates on a lathe:
A. the cutting tool
B. the chuck
C. the material / workpiece
D. answers B & C
E. none of the above

D. answers B & C

Turning is a metal cutting process used mainly for the generation of rectangular surfaces.
TRUE / FALSE

FALSE (cylindrical surfaces)

Which of the following is not a common workholding method on a lathe:
A. holding in a chuck
B. holding between centers
C. holding in the tailstock
D. holding in a collet

C. holding in the tailstock

When operating a lathe the tool bit should typically be positioned:
A. above center to obtain better surface finish
B. below center to enhance chip evacuation
C. directly on the spindle centerline
D. none of the above

C. directly on the spindle centerline

Milling is a metal cutting process used primarily for the generation of cylindrical surfaces.
TRUE / FALSE

FALSE (flat/rectangular surfaces)

What rotates on a milling machine:
A. the material / workpiece
B. the cutting tool
C. the spindle
D. answers B & C
E. none of the above

D. answers B & C

Common types of milling machines include:
A. knee and column mills
B. bed mills
C. turret mills
D. drill mills
E. A & B above

E. A & B above

Which of the following is the most common workholding method on a milling machine:
A. holding in a chuck
B. holding between centers
C. holding in a vise
D. holding in a collet
E. holding in your hands

C. holding in a vise

Explain the difference between relay and proportional control

Relay is on/off; send full voltage to motor producing one speed (like a light switch).
Proportional can vary the voltage or the speed; allows for the speed to be varied by the controller

What is the 80/20 rule and what are some benefits/disadvantages?

Used for rapid prototyping and is made out of extruded aluminum
+: High yield strength, simple assembly/disassembly, easily adjustable, little machining, relatively low density, versatile
-: High material cost, not weldable, can only use fasteners, limited to using straight pieces of extruded material

It is okay to leave the cutting tool or workpiece rotating when making a measurement under the following circumstance(s):
A. your hand is several inches away from making contact with the tool or workpiece
B. the tool or workpiece is rotating < 500 rpm
C. you feel confident you have one too many fingers on your measuring hand
D. you hope to meet a cute, wealthy doctor when your finger is reattached
E. none of the above

E. none of the above

How many axes of motion does a standard engine lathe have, how are they denoted (i.e. A,B, etc.), and what are they called?

2: x-axis and z-axis

What is the purpose of tolerances and when should they be used?

Tolerances note the allowable margin of error for each dimension. They should always be used on final part drawings because manufacturing dimensions without tolerances are useless. Tolerances are not necessary in conceptual sketches.

Fasteners are primarily designed to do what?
A. clamp parts together
B. act as pivots and axles
C. locate parts with relation to each other
D. answers A & B
E. answers A & C

A. clamp parts together

What keeps a bolted joint tight?
A. lock washers or safety wire
B. elastic stop nuts
C. anaerobic sealer ("Loctite", etc.)
D. adequate torquing/stretching of the bolt
E. hope

D. adequate torquing/stretching of the bolt

Based on the over- versus under-tightening example, properly torqued fasteners can withstand how many more force application cycles before failure?
A. ~ 5 times
B. ~ 1000 times
C. ~ 10 times
D. ~ 10000 times
E. ~ 100 times

B. ~1000 times

Calculation of required fastener tightening torque depends on two variables:
A. material strength and thickness
B. desired preload and fastener diameter
C. number and size of fasteners
D. length of fastener and thread type
E. none of the above

B. desired preload and fastener diameter

Fastener threads should ALWAYS be loaded in\_______________ and should NEVER be loaded in\_______________

tension
shear

Which of the following statements are true:
A. sheetmetal refers to workpieces with a high ratio of surface area to thickness
B. sheets are defined as ≤ ¼′′ in thickness
C. plates are defined as \> ¼′′ in thickness
D. pulling, pushing and stretching are the most common sheetmetal operations

All are true

Manufacturing time is an example of a qualitative assessment?
TRUE / FALSE

FALSE (quantitative assessment)

What are three things that can cause calipers to measure inaccurately?

failure to zero the calipers before each use
debris, chips, or burrs on measured surfaces
failure to hold the jaws perpendicular to the measured surfaces
inadequate or excessive closing pressure

To reduce part cost, use (OTS / custom) parts

OTS

To reduce part cost, use (larger / smaller) feature tolerances

Larger

To reduce part cost, use (coarser / finer) surface finish specifications

Coarser

To reduce part cost, use (fewer / more) finished surfaces

fewer

To reduce part cost, use (fewer / more) dimension datums

fewer

To reduce part cost, use (stronger / weaker) material

weaker

To reduce part cost , use (tapped / thru-bolted) holes

thru-bolted

To reduce part cost, use (blind / thru) holes when reasonable/possible

thru

To reduce part cost, use (cone-bottomed / flat-bottomed) holes

cone-bottomed

To reduce part cost, use (arbitrary / nominal) part dimensions

nominal

To reduce part cost, design parts to be (larger / smaller)

smaller

To reduce part cost, design parts for (max / min) raw-stock removal

min

To reduce part cost, design pars to use (larger / smaller) cutting tools

larger

To reduce part cost, design parts (fewer / more) fillets

fewer

To reduce part cost, design around (custom / standard) cutter sizes

standard

To reduce part cost, (avoid / use) mirror image (versus identical) parts

avoid

To reduce part cost, make (acceptable / great) detailed part drawings

great

You must come to lab each week with long \___________ , proper \___________ , and printed equipment \____________ \____________

pants
shoes
safety sheets

Never leave the \__________ \______________in the lathe chuck; even for one second

chuck key

Never reach over the rotating \________________on the lathe for any reason because of the dangerously protruding \__________ \___________

chuck
chuck jaws

Always \_____________ and \________________the milling machine spindles before changing the plastic \______________ \______________

raise and lock
table covers

Always check the milling machines and lathes are in \________ range before turning them on

high

Always adjust \_____________ \______________with the mills, lathes and drill presses running

drill speed

Never pull \_________________ off the machines using your hands; use a rag instead

chips

Always engage the workpiece \_______________to avoid chipping the fragile cutting inserts / edges

gently

Always wear \____________ when working with sheetmetal, except when using \___________________________, such as bandsaws, drill presses,grinders, and sanders

gloves
power tools

Never cut any material except \______________on the Marvel bandsaw (hint: the 80/20 extrusion is made from the same general type of material)

aluminum

Always take time to \_________________ each workpiece after cutting to remove the sharp edges which can injure a teammate or TA

file

Define the electric arc welding process:
using a(n) \____________ arc to heat separate pieces of \______________ material to be joined to a temp high enough to cause \____________ and coalescing

electric
identical
melting

List the formal acronym and common name for the three most common types of electric arc welding (in order of increasing quality):

1. SMAW (Shielded Metal Arc Welding)
2. GMAW (Gas Metal Arc Welding)
3. GTAW (Gas Tungsten Arc Welding)

Dissimilar metals can be joined using the arc welding process if the proper filler metal is used:
TRUE / FALSE

FALSE
To weld material together, both pieces must be heated enough to cause melting and coalescing.

The electrode (electrical conductor) used when MIG welding is consumed as the weld is made:
TRUE / FALSE

TRUE

What is the purpose of flux or shielding gas?
to prevent rapid \__________________ by preventing \__________________ from coming into contact with the molten metal pool

oxidation
oxygen

List 3 advantages of MIG welding

1. Fast
2. Easy to learn
3. Requires little post-weld cleanup

List 3 advantages of TIG welding

1. it produces the strongest welds possible
2. it requires no post-weld cleanup
3. it can weld virtually any metal that is conductive

What's the primary difference between MIG and TIG welding?

MIG welding automatically feeds the filler wire into the weld pool; whereas TIG welding uses a tungsten electrode to conduct the electricity and provide the heat source, and the actual filler wire is fed manually into the molten pool

If any fasteners do not freely thread together BY HAND, you should STOP and ask a TA BEFORE damaging expensive components:
TRUE/FALSE

TRUE

Before changing tools in the lathe the spindle must first be raised to and locked in its upper-most position:
TRUE / FALSE

TRUE

The lathe chuck key should be removed from the chuck after clamping the tool securely:
TRUE / FALSE

FALSE (workpiece)

Before changing the lathe between HI and LOW range you must ask for TA help:
TRUE / FALSE

FALSE (mill)

Lathe, mill and drill press spindle speeds must
be adjusted while the machines are OFF:
TRUE / FALSE

FALSE (ON)

Lathe turning

Metal cutting process used for the generation of cylindrical surfaces

The generation of any cylindrical surface with a single point tool is referred to as "\______." In this operation, the direction of the feeding motion is predominantly axial with respect to the machine spindle.

turning

A single point tool is fed linearly and parallel to the axis of a workpiece to enlarge a hole made by a previous process in the operation known as "\_______."

boring

Surfaces are typically positioned perpendicular to the axis of the workpiece in the "\______" operation. This operation is dominated by radial feed.

facing

In a "\______" operation, both modes of tool feed are simultaneously desired to created tapered and contoured surfaces

profiling

In the "\_______" process, a hole is produced by feeding a drill into a rotating workpiece along its axis.

drilling

In an operation known as "\________," a regular cross-hatched pattern is produced in work surfaces through metal forming.

knurling

For a "\_____" operation, a tool cuts the corner of a cylinder at an angle.

chamfering

During a "\______" operation, external or internal threads are achieved by feeding a pointed tool linearly across the outside or inside surface of a rotating part.

threading

For a "\______" operation, the end of a part is cut off by feeding a tool radially into a rotating workpiece at a particular location along its length.

parting

When a workpiece is \_______ \__ _ \______ , it is clamped in a rotary chuck containing 3 or 4 jaws for security.

held in a chuck

When a workpiece is \____ \__ _ \_____, it is held in precision cylindrical bushings.

held in a collet

When a workpiece is \____ \_______ \_______ , it is supported between 2 pointed mandrels. It is most often used for long, slender workpieces.

held between centers

All standard tool holders are designed to cut with the cutting edge or point located on the centerline of the machine and workpiece.
TRUE/FALSE

TRUE

This lathe type represents the first step toward high production turning machines.

turret lathe

This lathe type replaces the tailstock and tool post compound assembly with tool-holding turrets.

turret lathe

This machine is better for lower production needs.

engine lathe

This machine includes the "skill of the worker" within itself, so inexperienced operators can reproduce identical parts.

turret lathe

This machine requires a skilled operator and requires more time to produce identical parts.

engine lathe

This machine type is more ideal for higher production needs.

turret lathe

A process of generating machined surfaced by progressively removing a predetermined amount of material or stock from the workpiece which is advanced at a relatively slow rate of movement or feed to a milling cutter rotating at a comparatively high speed.

milling

The use of the end and periphery (or side) of the cutting tool to create a shoulder or pocket

end milling

The use of the end or tip of the cutting tool to create a flat workpiece surface.

face milling

What is the most common type of workholding device for a milling machine?

vise

Drilling accounts for the majority of holes produced in industry today.
TRUE/FALSE

TRUE

What is the functional difference between a bolt and a screw?

Bolts are headed fasteners with external threads that meet an exacting, uniform thread specification so they can accept a non-tapered nut.
Screw are headed, externally-threaded fasteners that do not mate with a non-tapered nut. Screws are threaded into material that they hold.

Regardless of country of origin, the two available varieties of fasteners are \____ and \_____.

fine and coarse

How are the threads on all quality fasteners made and why are they made this way?

All quality fasteners have rolled threads produced by rolling or sliding dies. Rolled threads produce superior surface finish and improved material properties that create a high fatigue resistance.

What is the sole purpose of a fastener?

The sole purpose of a fastener is to clamp parts together.

Why should fastener threads never be placed in shear?

The threaded portion of the fastener has a slightly smaller diameter than the unthreaded shank, which would allow the fastener to quickly loosen if transverse loading is applied.

How should engineers prevent relative sliding of parts fastened to each other?

To prevent relative sliding of parts fastened to each other use dowel pins when possible and place the shank in shear when necessary.

What keeps a fastener tight or secure? What does not?

Proper installation torque is what keeps a fastener tight or secure. Anaerobic adhesives, "lock washers", safety wire, elastic stop nuts, castellated nuts and cotter pins will not keep a fastener tight and secure.

For the same size fastener, is a coarse thread stronger than a fine thread?

The fine thread (1/4-28 UNF) is stronger because it has a larger minor diameter and thus a greater cross sectional area. This means it can take a larger load. Since the coarse thread has a smaller minor diameter, it has less strength and an increased chance of failing.

For the same size threaded hole in a soft material like aluminum, is a coarse thread stronger than a fine thread?

In a soft material, a course thread (1/4-20 UNC) is stronger than a fine thread because it has a smaller minor diameter and a larger thread pitch so it will have a greater shear area and thus be stronger. The larger minor diameter of the fine thread (1/4-28 UNF) causes the cross sectional area of the threads to be less and thus weaker.

How are TPI & thread pitch related?

The thread pitch is determined by dividing 1 by the TPI (thread pitch \= 1/TPI).

Equation to find installation torque (T)

T \= 0.2 x Fi x d
Fi: desired preload (installed tensile force in bolt)
d: nominal bolt (shank) diameter

Equation to find installed tensile stress (ot)

ot \= 0.9 x oy
oy: ultimate yield strength (grade)

ot \= Fi/At
At: tensile stress area (size designation/tpi)