DML Review

define lathe turning

metal cutting process used for generation of cylindrical surfaces

turning

generation of cylindrical surface with single point tool

facing

generation of surface perpendicular to workpiece axis

profiling

turning and facing to create tapered surace

chamfering

tool used to cut angle on corner of cylinder

parting

tool is fed radially into rotating work along length to cut off end

threading

pointed tool is fed linearly across outside or rotating part to produce external/ internal threads

boring

enlarging a hole; single point tool fed linearly and parallel to axis of rotation

drilling

producing hole by feeding the drill into the rotating work along axis

khurling

metal forming to produce regular cross hatched pattern

what are the 3 common methods of work holding for lathes

held in chuck

held between centers

held in a collet

T/ F all standard tool holders are designed to cut with the cutting point located on the centerline of the spindle

TRUE

what are the physical and functional differences between an engine lathe and a turret lathe? what is the primary advantage of each?

engine: versatile, more time, needs skilled worker

Turret: tools work in smaller diameters, high production, tool holding replaces tailstock and tool post

define milling

process of generating machined surfaces by progressively removing predetermined amount of material from the workpiece

from what material are most solid milling cutters and drills made?

High Speed Steel

list six factors that influence and determine cutting speed and feed rate

type of material

rigidity of set up

physical strength of cutter

cutting tool material

power available at spindle

type of finish desired

define face milling

the process of milling flat surfaces that are at right angles to the axis of rotation of the cutter.

define endmilling

used on vertical and horizontal milling machines for facing, slotting, and profiling

what is the most common type of work holding device for a milling machine

vise

define drilling

most commonly associated with producing machined holes; simple, quick, and economical; used for cutting and extruding

T/ F drilling accounts for the majority of holes produced in industry

TRUE

define reaming

enlarge a previously drilled hole to provide higher tolerance and improve surface finish

define tapping

provide internal threads on previously drilled hole

counterboring

produces larger step in a hole to allow bolt head to be seated below the surface

countersinking

step is angled for flat head screws

centering

accurately locating a hole to be drilled afterwards

spotfacing

provide flat- machined surface

define nominal size

size used for general dimension

basic size

conversion of nominal size to decimal

tolerance

the allowable variation in a given dimension that the part can still function as intended

bilateral tolerance

using both + and - variations

unilateral tolerance

using + or - to express tolerance

limit dimension

upper and lower sizes for a single feature

define fit

range of tightness designed into parts that assemble one into another

define allowance

tightest possible fit

-minimum clearance

-maximum interference

define datum dimensioning

all dimensions start from a single reference point

chain dimensioning

single dimensions placed adjacent to another

define accuracy

how close you are to a target area

define precision

how closely all points are grouped together

what is the functional difference between a bolt and a screw

bolt requires a nut where a screw does not

how are the thread on all quality fasteners made? why are they made this way?

they have rolled threads; strength, resistance, cost, and fatigue

what is the sole purpose of a fastener

to clamp parts together

why should fastener threads never be placed in shear? how should engineers prevent relative sliding of parts fastened to each other

threaded portion is smaller than unthreaded shank and shear allows fastener to loosen (less surface area); relative motion makes thread act as file; engineers should use dowel pins

what keeps a fastener tight? what does not?

lock washers, anaerobic adhesives, safety wire, elastic stop nuts, castellated nuts and cotter pins DO NOT. a properly designed and torqued fastener joint DO.

what area of the fastener would fail?

tensile failure along threaded root

are coarse or fine threaded fasteners stronger? why?

fine. higher minor diameter increases cross sectional area and decreases shear area for failure.

what area of a threaded hole will fail?

shear failure along major diameter

are coarse or fine threaded holes stronger? why?

coarse. smaller minor diameter and larger thread pitch increases shear area.

explain how fastener grade and TPI affect the required preload

higher grade and threads/ in increase the required torque

what is the equation to calculate required fastener torque as function of desired preload and bolt size?

ot = 0.9 x oy

Fi= ot x At

T = 0.2 x Fi x d

how do you calculate the thread pitch?

1/ threads per inch

what type clearance hole should be specified when positioning accuracy is important?

close fit

what type clearance hole should be specified when quick manufacturing time is important

free fit

what should be included in hole note specification

tap drill diameter + depth

thread specification + depth

quantity of holes desired

define lathe turning and differentiate from lathe drilling

lathe turning- cutting tool is moved parallel to the axis of rotation to remove material from outer edge

lathe drilling- drills hole through rotation axis

how many axes of motion do the manual lathes have? what are they? which axis is aligned with the spindle axis

2, x and z, z

what typically gets clamped in the lathes chuck and tailstock

chuck- workpiece

tailstock- drills

explain the difference between roughing cuts and finishing cuts

roughing- more than 0.020 inches of material being removed (time)

finishing cuts - less than 0.020" of material is being removed (surface finish)

list three controllable cutting parameters that influence the metal removal rate when turning

speed

depth

feed rate

define milling and differentiate from drilling.

milling- moving workpiece past tool to remove material from outer edge and produce place

drilling- moves tool to create holes

what type of milling machine is used? how many axes? which axis is aligned with the spindle?

knee and column; 3; z

what is the purpose of an edge finder? what are the two mechanical types?

to find datums

cylindrical and conical

list cutting tool sequence use to create #10 threaded hole

center drill

tap drill of size 30

tap guide, tap handle, and 10-24 unc tap

what is the limiting factor for how deep you can cut per pass with an endmill in a particular material

machine stiffness, cutting tool stiffness, workpiece stiffness

list one physical difference between endmills and drill bits

drill bit has tapered end while end mill has flat end

T/ F drill bits can only cut their ends whereas endmills can cut with both their ends and sides

TRUE

what is a physical and functional difference between drill bits and reamers? when are reamers used?

physical- drill bit has helical cutting edge while reamer has straight edge

functional- reamers remove small amount of material while drill bits start a hole

reamers are used to finish a hole when a tight tolerance is required

what is the purpose of a tap handle and a tap guide

tap guide- keeps the tap normal to the surface so threads are created properly

tap handle- allows tap to manually be rotated into worpiece

what is the purpose of a center drill

center drills are used to locate and start hole so drill will not deflect

what is the purpose of a tap drill? why does size matter?

final drill size used to make a properly sized hole prior to tap; too small will break, too large and threads will fail

what is the purpose of a countersink?

so the fastener screw sits flush with the face of the piece

what type of internal thread is better for softer material

coarse- smaller minor diameter increases thread area resulting in higher strength and fatigue resistance

T/ F Bolt holes are always clearance hole

TRUE

what is the quickest way to drill one accurate hole through the center of a cylindrical workpiece

use tailstock of a lathe and pecking motion

what should good design engineers when choosing material?

select the weakest material that meets strength requirement

how should engineers design cost effective part features with regard to the tool size?

larger tools

what categories are CNC machines better suited?

complex

mass production

what are two mistakes that can cause dial calipers to measure incorrectly

not measured normal to surface

user doesnt tighten all the way

what is the typical tolerance range for features machines on milling machines and lathes?

+- 0.005" to +- 0.020"

what does DRO stand for

digital readout

which of the following are true:

a. sheetmetal refers to workpieces with a high ratio of surface area to thickness

b. sheets are defined as <= 1/4" in thickness

c. plates are defined as >= 1/4 " in thickness

d. pulling, pushing, and stretching are the most common sheetmetal operations

A, B, and C

The Lab has the following sheetmetal capabilities:

A. shear

B. Brake (bending machine)

C. punch press for creating holes

D. deep drawing/ stretch forming

A, B, C

what is the structural benefit of bending sheetmetal edges/ flanges?

makes it more rigid

Which of the following are key element to decision matrices?

A. clearly defined & weighted objectives

B. Justified magnitude assignments with traceable supporting data

C. always try to use linear score assignments

D. highest scoring concept wins

all of the above

T/ F manufacturing time is an example of a qualitative assessment?

False

What are (4) the things that can cause calipers to measure inaccurately?

failure to zero the calipers before use

debris, chips, or burrs

failure to hold the jaws perpendicular to the surface

inadequate or excessive closing pressure

T/ F Your group must have a fully dimensioned, appropriately toleranced part drawing for each part manufactured in the lab

TRUE

T/ F ECN's are used to formally track design changes and corrections through the project prototyping and life- cycle phase

TRUE

Use OTS/ custom part

OTS

use larger/ smaller feature tolerances

larger

use coarse/ finer surface finish specifications

coarser

use fewer/ more finished surfaces

fewer

use fewer/ more dimension datums

fewer

use stronger/ weaker material

weaker

use tapped/ thru - bolted holes

thru- bolted

use blind/ thru holes when reasonable

thru

use cone- bottomed/ flat- bottomed holes

cone- bottomed

use arbitrary/ nominal part dimensions

nominal

design parts to be larger/ smaller

smaller

design parts for max/ min raw stock removal

min