MCG1101- Terms to still study

Helical Gear

like spur gear with teeth cut at angle to axis, less noise/vibration

herringbone is opposite angles each side

spur gear

teeth parallel to axis

Bevel Gear

the cone shaped ones

worm

The gear around a shaft, usually 1 to 3 teeth

worm gear

the gear attaching to a worm

Gear equation

w1/w2 = N2/N1 = d2/d1 = M2/M1 (M is torque)

Smaller gear has ____ Torque

** Smaller** - M2 = M1 (N2/N1)

Smaller gear as ____ Speed

**Larger** - w2 = w1 (N1/N2)

If one gear has higher speed it has ____ torque

smaller

Magnetic, dull grey, rust spots, easy to bend, weighty

Steel

Silvery grey, rough flaky pattern, magnetic, can have satin coat with dull and not flaky appearance

Galvanized steel

Silvery, lighter color than steel, shiny, hard, could be magnetic or not

Stainless steel

Lighter, light silvery, dull or shiny, soft, non magnetic

Aluminum

brass bronze copper

order of yellow to copper colour

dull gray, magnetic, rough cast surface, if machined it looks like steel

Cast Iron

looks like aluminum but in die cast parts

zinc

chrome plating

shiny smooth consumer products

plastic deformation

can't be bent back

Hardness

resistance to plastic deformation and scratching

stiffness

to resist elastic deformation

strength

to carry load

alloy

a mixture of two or more elements, at least one of which is a metal (steel, brass)

cold working / hard working

lots of plastic deformation at room temp to strengthen

heat treatment

controlled heating and cooling for hardening

tempering

reheating heat treated steel and cooling slowly to make less brittle

softening / annealing

heat to 2/3 melting and letting cool

ductile

extensive plastic deformation before breaking

brittle

fails without any plastic deformation

tough

absorb a lot of energy before failing (Therefore lots of plastic deformation, fails ductile fasion)

Brittle Crack Propagation

Rapid, sharp, stress concentration at tip, greatly weaken the material

Ductile Crack Propagation

Make the crack round, reducing stress concentration and harder to propagate

tension faliure

δ = T/A (δ=stress, A = Xsection area, T = tesion)

Shear Faliure

Sliding of one piece past another

₇ = V/A (₇ = shear stress, V force, A = wL of matirial)

Lap Joints

screws, rivets, welding, overlapping , not in line, couple pulls them appart

Double lap joints

creates pure sheer, 2 sheer surfaces, load spread out over two shear surfaces

shear joints with pins, rivets, screws

angled position creates moment

SI system Screw

M10 x 1.5 x 30 hex head screw (or bolt)

M - metric

American system screw

1/4" - 20 x 1 1/2" hex socket cap screw

given in fractions of inch

pitch after dash

Screw information order

1. Nominal diameter

2. thread pitch

3. length

4. head style

Metric VS. Imperial thread pitch

Dist between threads VS. Threads per inch (TPI)

Diameter rounding for threads

Up to nearest mm size, or to 1/16" - 1/8"

length of FLAT HEAD

the entire screw, including head

Journal Bearing

Smooth shaft in smooth hole (Plain bearing, bushing)

Ball bearing

small loads

Roller Bearing

Supports more load than ball bearings

Tapered can support thrust in one direction (used in 2s)

Needle Bearings

thin roller bearings

Tapered roller bearing

gaskets

flat seals of soft materials to seal mating surfaces

shaft seals

rubber/plastic to seal around rotating shafts (protect bearings)

O-rings

precise rubber rings, used as gaskets or shaft seals, in addition to piston rings in pneumatics or hydraulics

Press fit

gears/bearings often mounted to shafts to perminently lock in place

keyway

used to mount the gear to shaft while maintaining normal angle

Motor Rotor (Armature)

Number of electromagnets (poles) arranged in a circle

Its the big copper one in the middle

Stator

winding of fine wire surrounding the rotor that stays stationary. electromagnet with current, called field

This is the copper winding that is surrounding the armature

commutator

small copper circle at one end of rotor, acts as rotating switch, supplies power to different sections of rotor as it spins, so that force is always equal and directed at an angle to field

Rolling

shaping piece by passing through rollers (Hot or Cold), pretty much any long extruded shape produced this way

Cold rolled for simple shaped, not structural

hot-rolled appearance

rough dark surface, few loose flakes

Cold-rolled appearance

smooth (Not Shiny) surface, harder than cold rolled

Pipes and tubes

welding seam, seamless rolling, centrifugal casting

Extrusion

pushing/pulling metal through suitably shaped die, to produce continuous shape. More complex shapes than rolling

Wire-drawing

rolled rod pulled through progressively smaller dies to reduce to correct size

Sand casting

Rough surface finish, visible parting line, no fine details or thin cross sections (new mold for every cast, 2 parts, metal in the grate, air out the vents)

Gravity casting

permanent molds, smooth finish, metal poured into mold, can't flow long distances or into thin X sections, no fine details, no parting lines (never steel, cast iron, stainless)

die casting

metal forced under high pressure, smooth surfaces, fine details, thin sections, no parting lines (never steel, cast iron, stainless)

injection molding

plastic only, complex like die casting

drilling

smaller and inaccurate, can be done by hand, press, or lathe

Reaming

Making a drilled hole more accurate

Boaring

Enlarging a drilled hole, done on lathe or mill

Turning

cleaning and shaping cylinder shape on lathe

Facing

smoothing end of piece on lathe

Face Milling

Just milling flat surfaces, not facing done on lathe

Pocket, corner milling

making deeper pockets in material

slotting

making a slot in mill, end mill, side mill, form cutter can ve used

form cutting

gear teeth cutting in mill

Hobbing and shaping

Faster way to cut gears, can't really tell them apart. Asume all gears hobbed

precision grinding

very smooth, flat or round with no machining marks, often shiny, pretty much only steel

tapping and dieing

making thread in or on things

Boaring mills

Horizontal (cutting spins) or vertical (Material spins)

Forging

steel, simple, straight parting line, no cavities, very strong

sheet metal forming

stamping (punching, or forming)

deep drawing

punch to form into a die, like forming but really deep