Metals Units 45-75

Structure

1 to 15 to dense to open, how much space in between grit

grade scale

A to Z

Describe a thread designated as M 56 X 5.5

M-Metric Nominal size-56 Pitch-5.5 Pitch dia tolerance-19g Outside dia tolerance-56g

How is a grinding wheel dressed when grinding a vertical surface..why is it necessary

dress side of wheel to give clearance

What is the purpose of the backlash eliminator?

eliminates backlash between the nut and the table lead screw

3 factors that affect the efficiency of a milling operation

excessive heat, abrasion, and chipping or crumbling of cutting edges

What are the features of a plain vise

may be bolted to the table so that the jaws are parallel or at right angles to the axis of the spindle

How is the pitch designated for metric threads

millimeters

vertical milling machine can be used for

milling boring,drilling, and reaming

State the purpose of a follower rest

move with the carriage to prevent work from springing up

feed =

number of teeth in cutter x cut per tooth

How deep should a roughing cut be

one-half the total amount removed from the workpiece in one cut

Why are rotary tables used?

permits the milling of radii and circular slots

numbers for wheel

prefix of manufacturer, abrasive type,grain size,concentration,bond type,bond modification,depth of abrasive,manufacturers record

Define the process of knurling

process of impressing a diamond-shaped or straight-line pattern into the workpiece to improve its appearance

Define truing

process of making the grinding wheel round and concentric with its spindle axis

What is the purpose of a headstock spindle (part of the lathe)

provides a drive through gears from the motor to the work-holding device

What is the purpose of the cross slide (part of the lathe)

provides a manual or automatic cross movement for the cutting tool

What purpose do T-slots serve

receive bolts for clamping workpieces

4 purposes of grinding fluids

reduction of heat,lubrication, removal of swarf, and control of grinding dust

State purpose of rough and finish turning

rough turning removes the most metal as possible in the shortest length of time. Finish turning follows rough turning, produces a smooth finish surface and cuts the work to an accurate size.

How is grain determined and why is it important

say you have a #8 grain size, it would pass through a screen having eight meshes per linear inch and would be 1/8 inch across, IMPORTANT because undersize grains in a wheel will fail to do their share of the work

finishing cuts you use a ______ feed

slower

roll dresses

small grinding wheel mounted to wear the diamond grit down

What is the purpose of a light trial cut at the end of the workpiece

so the work is the appropriate length and doesn't need extra supported

two flute end mill

2 teeth

How far may work extend beyond the chuck jaws before it must be supported

3 times the diameter extending beyond the chucks jaws

At what maximum speed should a 3.50 in cemented carbide milling cutter revolve to machine cast iron

50-80 ft/min

What common ratios are found on rotary tables

72:1 80:1 90:1 120:1 larger ratios found on larger tables

State two methods by which indexable carbide inserts are held in a tool holder

Cam action and clamp

Name two common materials from which end mills are made

Carbide, and cast iron

boring

Enlarges the hole slightly and making it rounder and straighter

7 main causes of milling cutter failure and state how they can be minimized

Excessive heat (add coolant), Abrasion (follow rules CS and feeds), chipping or crumbling, Clogging (two coolant nozzles), Built up edges (good cutting fluid), work hardening (break up the glaze), and Cratering (tool surface treatments)

OD, ID

Outside Diameter Inside Diameter

3 types of vertical milling

Ram type, 2 axis control, and heavy duty

Why is it necessary that the taper on the lathe spindle nose and the mating taper in the chuck be thoroughly cleaned before mounting

Steel chips or dirt will destroy the accuracy of the spindle nose and mating taper in the chuck

Why is the selection of the grade of wheel important to the grinding operation

Wheels which are to hard do not release the grains readily; consequently the grains become dull and don't cut effectively

3 manufactured abrasive and why they are used extensively used today

aluminum oxide (used for grinding the hardest steels), silicon carbide (used for grinding materials with low tensile strength, and boron carbide (next to diamond second hardest material and cost less)

most common wheel used to grind

aluminum oxide, second common silicon carbide

Name four natural abrasives

aluminum oxide, silicon carbide, boron carbide, and diamond

define chip per tooth

amount of material that should be removed by each tooth of tooth of the cutter

What should be done to prevent the cutting tool from binding in a deep groove

apply cutting fluid to the

What is the purpose of a multi thread

are used when it is necessary to obtain an increase in lead and a deep, coarse thread cannot be cut

Describe the cutting action of zirconia-alumina abrasive

as it cuts and becomes dull the dull particles fall off and sharp ones replace the old ones

Why should a hole be bored before it is reamed

bc boring takes most of the material and reaming takes a little bit and touches it up

Why should chips not be cleaned with a cloth

because if someone picks that rag up they might get cut

How can the tap be kept in alignment when tapping on a vertical mill

by mounting the tap in the vise

How is the size of a lathe designed

by the largest work diameter that can be swung over the lathe ways

What can happen if an extensively heavy cut is taken or too fast a feed is used

can cause the cutter to break

What precautions must be taken when turning work supported by solid centers

care must be taken (adjusting and lubricating)

Know the parts of a lathe

carriage headstock look at picture on pg 354

What are two requirements that must be met to enable a lathe cutting tool to cut

certain angles and clearances

CBN

cubic boron nitride manufactured diamond

How large should a face milling cutter be in relation to the width of the work

cutter should be 1 inch larger than width of work

Define CS and state how it is expressed

cutting speed and can be defined at which the rate at which a point on the work circumference travels past the cutting tool.

CSx4/D

cutting speed x 4 divided by diameter

facing

cutting to square outside edges (cross slide used to make facing cuts)

What is a template

determines the accuracy of the form produced

Explain how the ratio of 40:1 is determined on a standard cutting head

divide 40 by the number of divisions to be cut

Name three methods of holding cutters on a milling machine?

fixture, vertical milling attachment, and arbors

Why are aluminum oxide and silicon carbide abrasives used?

for high tensile strength material and silicon is used for low tensile strength materials.

Why are four-jaw chucks used

for work that must remain absolutely true , and they can hold round square or irregularly shaped workpieces

What are the basic functions of a grinding wheel?

generation of cylindrical,flat and curved surfaces, removal of stock, production of highly finished surfaces, cutting-off operations, and production of sharp edges and points

Describe the principle of crush-form dressing

grounding the crush roll to the right tolerance over and over

Factors to consider when the grade of wheel is being selected for a particular job

hardness of the material, area of contact, condition of the machine, speed of grinding wheel and the machine, rate of feed , and operator characteristics

collets

hold end mills tools

Why is the table alignment so important to most milling operations

if not aligned right the keyway will not be milled parallel to the axis of the shaft

Why is proper CS important

if the CS is to high the blade dulls quickly, if it's to low time will be lost during the cutting process

Why is is important that the vise be aligned with the tabel travel

if the head is not 90 degrees the holes wont be square

Why is the proper balance of the grinding wheel essential

improper balance will affect the surface finish and accuracy of the work

lathe feeds in

inch per revolution

climb cutting can

increase cutter life by 50%

How has the role of grinding changed over the years

initially they were used on hardened work, today grinding is applied extensively to the production of unhardened parts

State the purpose of the mandrel

is a precise tool, when pressed into the hole of a workpiece, provide centers for a machining operation

Define the structure of a grinding wheel and state how it is indicated

is the density of the wheel, indicated by numbers from 1 to 15

Define dressing

is the process of removing the dull grains and particles

What is the function of the bond and how does it affect the grade of the wheel

is to hold the abrasive grains together in the form of the wheel, the grade of the wheel is determined by how strong the bond is

What is the purpose of the compound rest (part of lathe)

it can be swiveled to any angle for tapering turning operations

vertical mill look at picture of the parts

knee, base, column, spindle, head, ram

List the advantages of the taper attachment

lathe center remains alignment,setup is simple, length of workpiece does not matter, wider range of tapers may be produced

Describe 3 types of standard tool holders and state the purpose of each

left-hand offset tool holder (offset to the right) is designed for machining work close to the chuck designated by the letter L, Right-hand offset tool holder (offset to the left) used for machining work close to the tailstock designated by the letter R. Straight tool holder can be used to take cuts in either direction designated by the letter "S"

Define lead

longitudinal distance the helix advances axially in one complete revolution of the work

grain size

lower the number the less grit

vitrified bond

made of clay at a high temp

What precaution should be taken before drilling holes on a vertical mill

make sure workpiece is held secure and holes are in the right place

turning

makes the diameter get smaller when you cut

How may the live center be checked for trueness after it has been mounted on the spindle

start the lathe and observe if the center is true, but for complete accuracy use a dial indicator

What type of cutter should be used to machine a large surface

suitable fly cutter should be used

How should work be checked for defects

test wheel before use, be sure it's mounted properly, see the wheel guard covers at least half the wheel

List advantages of an electromagnetic chuck

the holding power of the may be varied to suit the area of contact and thickness of the work, special switch neutralizes the residual magnetism in the chuck, allows the work to be removed easier

How is the pitch designated for UNC threads

the pitch is the distance from a point on one thread to a corresponding thread point on the next thread

Describe the process of face milling

the process of milling flat surfaces that are at right angles

Define helix

theoretical line generated on a cylindrical surface

List four purposes of threads

to fasten devices such a screws and bolts,provide accurate measurement,to transmit motion, to increase force

Why should the table saddle be locked before machining

to prevent movement during cut

Why is wearing safety glasses and not wearing loose clothing important

to protect your eye and so your clothes don't get caught in a machine

State three purposes of facing a workpiece

to provide a true,flat surface, square with the axis of work, to provide an accurate surface, to cut the work to a required length

purpose of reaming in a lathe

to quickly obtain an accurately sized hole

What is the purpose of a follower rest

travels with the carriage to prevent work from springing up

List the operations that can be performed on a lathe

turning, tapering,form turning,threading,facing,drilling,boring,grinding, and polishing

What factors affect the selection of the proper wheel structure

type of material being ground, area of contact, finish required, and method of cooling

For what purpose is direct indexing used

used for quick indexing of the workpiece

Uses for Boron carbide

used in the manufacture of precision gages and sand blast nozzles

what it the purpose of an arbor

used to hold the cutter during machining operation

Chuck cradle

used to support chucks when you switch them

What is the purpose of a steadyrest

used to support long work held in a chuck

Define worm and worm gear and describe their use

used when a great ratio reduction is required between the driving and driven shafts worm-cylinder on which is cut a single or multiple start ACME thread angle ranges from 14.5 to 30 Worm gear- teeth on a worm gear are machined on a peripheral groove

rough stock

want to remove it fast but leave some stock for fishing cut

4 points to be observed in grinding care

when not in use should be stored properly, wheels should be tested for cracks prior to use, select the proper type of wheel for the job, and grinding wheels should be properly mounted and operated at the recommended speed

Describe climb milling

when the cutter and the workpiece are going in the same direction

Conventional milling

when the cutter and workpiece are going opposite

end mill

will cut on end of it and outside

List two most important things to remember about filing in a lathe

work should only be filed in a lathe only to remove a small amount of material, and always remove the cutting tool from the toolholder before filing