CAE Exam 1 Extra terms

clearance fit

hole larger than the shaft

transition fit

depending on dimensions, teh fit can have either clearance or interference

interference fit

the shaft is larger than the hole

RC fits

• running and sliding clearance fits

• tighter to looser clearance fits from RC2 to RC8

FN fits

• force and shrink fits, used when a more secure fit is needed

• higher FN means a tighter fit

form control

shape of an indivdual feature

orientation control

angle or alignment relative to a reference

location control

position of a feature

runout control

variation as a part rotates around an axis

how to designate purchased part

using original equipment manufacturer (OEM) designation in BOM

R_a

averages absolute deviations

R_q

squares deviations before averaging and taking the square root, so extreme peaks and valleys have a stronger influence

R_z

a measure based on surface peak-to-peak valley heights

skewness

describes asymmetry, not peakedness

kurtosis

describes the peakedness and the distribution’s tails

waviness

more widely spaced surface variations than roughness

cutoff length

length used to evaluate the surface profile

lapping

usues abrasive particles suspended in a fluid or slurry to produce very fine surfaces

honing

finishes internal cylindrical surfaces and often creates a cross-hatched texture

grinding

uses an abrasice wheel to remove material

broaching

uses a multi-tooth cutting tool to produce a profile, often an internal keyway or spline

boring

enlarges or finishes an existing hole using a cutting tool

drilling

creates a new hole

reaming

finishes an sizes an existing hole

milling

uses a rotating multi-tooth cutter to remove material

turning

uses a cutting tool and rotating workpiece, commonly to produce cylindrical shapes

drilling vs. boring

drilling creates a hole, boring enlarges or finishes an existing hole

reaming vs boring

reaming sizes and finishes a hole, boring uses a cutting tool to enlarge or modify the hole

honing vs. lapping

both finishing processes, but honing commonly produces a cross-hatched internal surface

broaching vs. milling

broaching uses a succession of cutting teeth, often to make a specific profile in one pass; milling uses a rotating cutter

abrasive vs. nonabrasive

lapping, honing, and grinding are abrasives. broaching uses cutting teeth rathr than abrasice particles as its primary cutting mechanicsm

planing

the workpiece moves linearly relative to the cutting tool

shaping

the tool moves linearly relative to a stationary workpiece

extrusion

forces a billet through a die to make a long product with a nearly constant cross-section

rolling

passes material between rolls to reduce thickness or change cross-section

close-die forging

compresses metal within shapes dies to create a component

sand casting

pours molten metal into a sand mold to form a part

cope (sand casting)

upper half of the mold

Connecting rods and other complex automotive parts are commonly associated with what metal forming process

Connecting rods and other complex automotive parts are commonly associated with closed-die forging

drag (sand casting)

lower half of the mold

core (sand casting)

creates an internal cavity or hollow feature in the final casting

riser (sand casting)

reservoir of molten metal that helps compensate for shrinkage during solidification

UNC, UNF, UNEF

• UNC has fewer threads per inch than UNF.

• UNF has fewer threads per inch than UNEF.

• More threads per inch means a smaller pitch.

reading unified thread designations

• 3/16 = nominal diameter in inches

• 24 = 24 threads per inch

• UNF = Unified National Fine

• 2 = thread fit/tolerance class

• A = external thread (B = internal thread)

diameter used to calculate transverse shear

minimum minor diameter

tensile stress area

represents an effective cross-sectional area for tensile loading of a threaded fastener. It is smaller than the area calculated using the nominal major diameter

tap

cuts or forms internal threads inside a hole

die

cuts or forms external threads on a rod or shaft

taper tap

has a long lead-in and starts threads gradually

plug tap

general purpose tap

bottoming tap

has a short lead-in and is used to cut threads close to the bottom of a blind hole, usually after threads have been started

metric thread designations

• M means metric thread.

• 14 means the nominal diameter is 14 mm.

• 2.0 means the thread pitch is 2.0 mm.

bolt preload

the initial tension applied to a bolt when tightening it

bolt proof load

the load fastener is designated to withstand without permanent deformation under ther specific proof-load test conditions

open die forging

metal-forming process where a heated metal billet is shaped between flat or simple dies that do not fully enclose the material