MMET 181 Exam 1

TAMU MMET 181 Exam 1 (Fall 2023)

orthographic projection

2D, XY coordinate system

isometric projection

3D, XYZ, 120deg between planes, special paper

guide line

thin, solid line

visible line

thick, solid line

hidden line

thin, dashed line

center line

thin line with alternating dashes and dots

why section?

to showcase internal/unseen parts

where to section?

choose best fit plane

how to section?

choose plane, mark view with arrows, draw sectioned view, and add cross-hatching to cut sections

sectioning special cases

special features are not cut, if there are multiple cut planes they have different cross-hatching

caibration

process to correct instrument

tolerance

allowable dimension

accuracy

deviation from design dimension

precision

repeatability of measured data

resolution

smallest measurable quantity

digital resolution

smallest increment

analog resolution

½ smallest graduation mark

steps for reading vernier caliper

1. main scale (ends at 0)

2. vernier (where tick merks align with main scale)

steps for reading customary micrometer

1. identify range

2. bottom scale (nearest .025)

3. right scale (number below ref line 0, divide my 1000)

4. left scale (tick that aligns, divide by 10000)

steps for reading metric micrometer

1. identify range

2. bottom scale (nearest mm)

3. top scale (nearest ½ mm)

4. right scale (tick below ref line, 0.01 mm per tick)

steps to read dial indicator

1. notice tip travel direction

2. read small dial (whole #)

3. read large dial (0.01/tick)

profile projector

2D data, enlarges and projects surface

profile projector measurements

diameter, radius, angle distances, 2D coordinates, form (roundness, parallelism)

coordinate measuring machine (CMM)

3D data, probe to build coordinate system, 5deg freedom

CMM measurements

dia and radius, 2D coordinates, 3D coordinates, 2D and 3D form

contact type measuring tools

caliper, micrometer, indicator, CMM

non-contact type measuring tools

profile projector, measuring microscope, laser sensor

crystalline material

tight-packed solid

amorphous material

free and flowy material

polycrystalline

loosely packed solid

strain

controllable stretch/deformation of a specimen

ductility

max strain before failure

stress

controllable ratio of force to area on a specimen

material strength

max stress before failure

hardness test

force hard indenter at a preset force and time into a material, then measure the indentation

vicker’s method

diamond indenter hardness test

brinnell method

steel sphere indenter for hardness test

effect of high temperature

reduction in strength, yield strength, and hardness

increase of ductility

it is easier to machine harder materials at high temps

true

alloy

homogeneous mix of different atoms

composite

heterogeneous mix of different materials

hypereutectoid

below 727deg C and more than 0.76% wt carbon

hypoeutectoid

below 727deg C and less than 0.76% wt carbon

steel

iron and usually <2% carbon

steel nomenclature

XXYY (alloy)(amount of carbon)

aluminum nomenclature

XXXX-YY

ferrous metals

spark, contain iron, magnetic

nonferrous metals

do not spark, nonmagnetic, do not rust

examples of nonferrous metals

aluminum, bronze, copper, brass

examples of ferrous metals

steel, cast iron, nickel

pros and cons of steel

pros: good tensile/compression, heat treatable, popular
cons: heavy, rust, corrosion

pros and cons of stainless steel

pros: rust resistant, good tensile/compression
cons: heavy, more expensive, difficult to machine

types of stainless steel

austenitic, ferritic, martensitic, duplex

pros and cons of aluminum

pros: light, minimum corrosion, easy to machine
cons: more expensive, softer, lower strength

pros and cons of cast iron

pros: easy to machine, good damping, good compression
cons: rust, heavy, poor tension

aluminum nomenclature: F, O, H, T

F: fabricated
O: annealed
H: strained hardened
T: tempered

copper nomenclature

CA XXX

pros and cons of copper

pros: highly conductive, easy to fabricate
cons: corrosive, lower strength

pros and cons of superalloys

pros: maintain high strength and hardness at high temps
cons: expensive, heavy, difficult to machine

UNF

united national fine

UNEF

united national extra fine

UNC

united national coarse

what does the thread classification depend on?

threads per inch (tpi) and thread pitch

removeable fastener

bolt, screw stud
can be unassembled and reassembled

fixed fastener

rivet, grommet, eyelet
cannot be taken apart, for fixed mechanical assemblies

bolt

tightened or released by nuts
flat shank
durable and reliable

screw

head has a specially formed shape
tapered shank
varying strength

stud

no tightening head
generally larger
longer lasting

tolerance stacking

when components are manufactured separately, tolerance of whole or individual parts are affected

clearance (loose) fit

large clearance between smallest pin and largest hole. pin may “rattle”

slip fit

minimum clearance between pin and hole

interference (press) fit

negative clearance between pin and hole. assembly done by:
(i) forcing larger pin into hole at room temp
(ii) thermally expanding the hole to insert pin

transition fit

hole and pin have overlapping tolerances, and mating parts can be assembled based on actual dimensions

traditional techniques of machining

contact types
milling, drilling, lathing

orthogonal machining

tool is 90deg (perpendicular) to feed direction
not conventional

oblique machining

tool is not perpendicular to feed direction
conventional way of machining

stronger tools need

smaller rake angles (negative rake)

less machining force is needed for

larger rake angles

a chip is

parallel shear plates

shear force and elasticity cause

a thicker chip than the depth being cut

lathe operations used in lab

turning, facing, tapering, knurling, drilling, parting

cutting speed on lathe

rotational speed of the workpiece

depth of cut on the lathe

depth of tool in rotating workpiece

reed rate on lathe

how fast the operator moves the tool

why bore

drills have set dimensions, used to make a hole larger

the pen base can be machined entirely on a

mill

drill/mill operations

reaming, tapping, counterboring, countersinking, spot facing

what is the only known location on a vertical mill

center of the drill/tool

cutting speed on mill

speed at which the tool rotates

depth of cut on mill

depth of tool in stationary workpiece

feed rate on mill

speed at which the table moves

upmilling

cut touches at 0 depth then depth increases as workpiece is cut

conventional milling

upmilling

downmilling

workpiece and tool travel in the same direction
tool engages high and depth decreases throughout the cut

climbmilling

downmilling (the REAL conventional)

broaching

tools are conical
unique shapes

process planning

step-by-step instructions on how to produce a part

tool life

machining distance or time

flank wear

wear on the side of the tool

crater wear

wear due to the rubbing of chips