Volume 2 Flashcards
Bow compass
The bow compass is used to draw large circles.
Phantom Lines
Phantom lines indicate the alternate positions of parts of an object, missing items, or repeated details.
Phantom lines are alternating ling lines and short double dashed lines.
Hidden Lines
Hidden lines show hidden features of an object. Hidden lines have short, evenly spaced dashes.
center lines
Represent the axes of symmetrial parts, can serve as extension lines for holes or other features of the object. Draw centerlines with alternate 1/8” and 3/4” dashes.
Leader lines
A leader line is a continuous line that ends with an arrow, it shows where notes would apply. Always draw themat an angle (60 or 30 degress) to the horizontal.
Standard hieght for numbers and letters
1/8”
Numbers and Letters
Place all horizontal dimensions and dimensional notes so they are read from the bottom.
Vertical dimesions read from the right of the drawing.
The fraction bar should be horizontal, and should be in line with the dimension.
Give all dimestions in inches up to?
72”
When you express decimal fractions as decimals?
Make the decimal points slightly heavier than the lettering lines and space the decimal points properly.
Rectanglar dimensioning
indicate distances with straight line measurements taken parallel or perpendicular to the reference lines.
Angular dimesioning
With angular dimesioning you use linear dimesions and angle dimensions.
How to identify counterbores?
Identify counterbores by using a leader and a note and abbreviat C BORE, also give the diameter and depth.
General tolerance rules?
For fractional dimensions, use a tolerance to the nearest 1/64”.
For x.xxxx”, the tolerance is +/- 0.0005”.
For x.xxx, the tolerance is +/- 0.002”.
For x.xx, the tolerance is +/- 0.010”.
Tolerance for fractions?
For fractional dimensions, use a tolerance to the nearest 1/64”.
Tolerance for X.XXXX”
For x.xxxx”, the tolerance is +/- 0.0005”.
Tolerance for X.XXX”
For x.xxx, the tolerance is +/- 0.002”.
Tolerance for X.XX”
For x.xx, the tolerance is +/- 0.010”.
Most common machinist square?
4 1/2”
How to store the machinist square?
Oiled and stored safely when not in use.
Calipers vs. Hermaphrodite Calipers
Calipers are considered measuring devices.
Hermaphrodite calipers are layout tools.
What is a surface gage for?
The surafce gage, also know as a height gage, scibes horizontal lines and lays out work on a surface plate.
What lengths do steel rules come in?
Steel rules or scales come in 6, 12, and 24 inch lengths.
Descibe plain carbon steel?
Plain carbon steel is the least expensive of all steels and the most widely used. This steel is sometims modified by adding chromium (Cr) and vanadium (V). Carbon steels are known to be erratic in their response to heat treatment.
Descibe Non-deforming tool steel?
Non-deforming tool steels are used extensively for intricately shaped tools where heat-treating distortion must be held to a minimum. These steels contain substantial amounts of manganese (Mn)–about 1.5 percent to 1.75 percent.
Descibe High-speed tool steel?
High-speed steels contain large amounts of tungsten and smaller amounts of Cr, V and in some cases, mlybdenum (Mo) and cobalt (Co).
Descibe Nonferrous tool materials?
Nonferrous tool materials include such metallic elements as W, tantalum (Ta), titanium (Ti), columbium (Cb), and Co in their carbide forms.
What is the main cause of tool deflection?
Dull tooling.
Name Two things to consider when figureing tool load?
First, find out whether the machines or tools can withstand externa loads without filure. Second, determine if the size and shape of a tool can withstand external load forces.
What is a jig?
Jigs hold, support and locate a workpiece while they guide the cutting tool.
What is a fixture?
Fixtures hold support, and locate the workpiece in relation to the cutting tool.
Descibe a template jig?
A template jig is used for limited production. They are the least expensive and simplest type of jig to use. Template jigs are only moderately accurate.
Descibe a table jig?
This jig is turned upside down to load and unloading. An advantage of using this type of jig is that chip removal is easy.
Descibe built up construction fixtures/jigs?
Built up jigs and fixtures have steel plates fastened together with screws, bolts or dowel pins. These are the most versatile type of fixtures.
Descibe welded construction fixtures/jigs?
Welded jigs and fixtures have steel plates or components welded together to form a tool with a specific purpose. One disadvantage of these fixtures is their limited interchangeability.
Descibe cast construction fixtures/jigs?
Cast jigs and fixtures are one-piece units, designed for a specific purpose. Cast constructions can be designed in almost any size, and they require a minimum amount of machining.
Descibe solid construction fixtures/jigs?
Solid construction jigs and fixtures are almost the same as cast jigs and fixtures. Solid construction ones are machined out of solid materal.
What is blanking?
Blanking involves cutting out a part with a punch or die. It is used to cut/punch out workpieces.
What is piercing?
Piercing involves punching holes in a workpiece.
What is Bending and forming?
Bending produces workpieces of a specific shapes and sizes.
What is drawing?
Drawing produces items like cups, boxes, and shells. In drawing, flat workpieces are pushed through a die by a dull-ended punch.
What is coining?
Coining is the process of forcing metals with thick cross sections into ies to form shapes or relief markings.
What is a clearance fit?
Clearance fits, or running and sliding fits (RC) as they are often called, provide for varying degrees of clearance.
Define a clearance fit, RC 1?
Close sliding fit. Accurately locates parts without detectable play.
Define a clearance fit, RC 2?
Sliding fit. Used for accurate location, but with greater maxium clarance than RC 1. Parts move and turn easily, but do not run freely.
Define a clearance fit, RC 3?
Precision running fit. The closest fit that runs freely. It is for precision work at slow speeds and for light journal pressures.
Define a clearance fit, RC 4?
Close running fit. Used for running fits on accurate machinery with moderate surface speeds, moderate journal pressures, and for accurate location with minimum play.
Define a clearance fit, RC 5?
Medium running fit. Used at higher running speeds and heavy journal pressures.
Define a clearance fit, RC 6?
Medium running fit. Used at higher running speeds and heavy journal pressures.
Define a clearance fit, RC 7?
Free running fit. For use where accuracy is not essential. Used where speed of assembly and disassembly are important.
Define a clearance fit, RC 8?
Loose running fit. For materials such as cold-rolled shafts and tubes made to commercial tolerances.
Define a clearance fit, RC 9?
Loose running fit. For materials such as cold-rolled shafts and tubes made to commercial tolerances.
What are the three types of transitional fits?
Locational clearance (LC), Locational transition (LT), Locational interference fits (LN).
Describe Locational clearance (LC) fits?
LC fits are used for stationary parts that can be freely assembled or disassembled. They run from snug fits for parts requiring location accuracy, through the medium clearance fits for parts such as faucets, to the looser fastener fits for freedom of assembly.
Describe Locational transition (LT) fits?
LT fits fall between clearance and interference fits where location fits where location accuracy is important, but a small amount of clearance or interference is acceptable.
Describe Locational interference fits (LN) fits?
LN fits are used for extreme location accuracy and rigidity. LN fits are not for parts that transmit frictional loads.
How many classes of interfrence (FN) fits are there?
There are five classes of interference (FN) fits.
Describe the interfernce fit, FN 1?
This is a light drive fit. Requires light assembly pressure and produces permanent assemblies. Suitable for thin sectinos, long fits, or cast-iron external members.
Describe the interfernce fit, FN 2?
This is a medium drive fit. For shrink fits on light sections. This is the tightest fit to use with cast-iron external members.
Describe the interfernce fit, FN 3?
This is a heavy drive fit. Suitable for heacier steel parts, or for shrink fits in medium sections.
Describe the interfernce fit, FN 4?
This is force fit. For shrink fits where heavy pressing forces are impractical. Use this fit to obtain the maxium grip between two parts, such as flywheel and the ring gear that fits around it.
Describe the interfernce fit, FN 5?
This is force fit. For shrink fits where heavy pressing forces are impractical. Use this fit to obtain the maxium grip between two parts, such as flywheel and the ring gear that fits around it.
What are the ways to chill a part?
Placing it in a freezer, packing it in dry ice, spraying it with carbon dioxide (CO2), or submerging it in liquid nitrogen.
What is the temperature of dry ice?
-109.3
What is the temperature of liquid nitrogen?
-320
What PPE is required for liquid nitrogen?
Face shield, goggles, rubber apron, and rubber gloves..
What is viscosity?
The viscosity of oil is its tendency to resist flow.
How does viscosity relate to temperture?
The higher the temperature of oil the lower the viscosity; lowering temperature increases viscosity.
Heavey oils become sluggish in cold weather because they’re highly viscous, while light oils become too fluid in hot weather because of their low viscosity.
What is viscosity index?
The viscosity index of oil is based on the change in viscosity of given oil with a change in temperture.
A low index denotes a great variation of viscosity with a change in temperature;a higher index denotes a lesser variation of viscosity with identical changes in temperatures.
What are greases?
Greases are petoleum-based oils that are thickened with additives like soap, compatible chemicals, and synthetic oils.
What are the grades that lubricant greases come in?
Lubricating greases come in three grades–soft, medium, and hard.
What are soft greases used for?
Soft greases are used for high speeds and low pressures.
What are medium greases used for?
Medium greases are used for medium speeds and medium pressures.
What are hard greases used for?
Hard greases are uses for slow speeds and high pressure.
Describe mineral oils and emsulsions coolant?
Emulsions are soap additves that permit oils to combine with water. Since emulsions are organic, they tend to become rancid over time.
Describe synthetic fluids coolant?
Synthetic fluids are excellent for grinding operations and high-temperature machining operations.
Describe semisynthetic coolant?
These are a combination of sythetic fluids and emulsions. They have lower oil content than emulsions and have small amounts of mineral oils added to them for enhanced lubricating qualities.
Describe cutting oils coolant?
Plain cutting oils are useful for light cutting operations on highly machinable materials, such as brass and Al.
Describe Gaseous coolants?
Compressed air forces a stream of cool ait into the cutting area to help remove chips. A disadvantage of the compressed-air method is it does little to prevent friction and breakdown at the cutter tip.
What is the most common method of using coolant?
The most common method is “flooding,” which supplies a generous amount of collant over the workpiece and the cutter.
When should you use the “mist” type of coolant method?
You should only use it for low-speed and low-cutting force operations.
How do you determine the size of the countour machine?
The size of the contour machine is determined by the throat depth, which is the distance from the the saw band to the column.
What items of a countour machine is containd in the head?
At the top of the countour machine, the head is the large unit that contains the saw band idler wheel, drive motor switch, and band tension control.
What items of a countour machine is containd in the column?
The column contains the speed indicator dial, which is driven by the cable from the transmission. This dial indicates the speed of the band, whichis displayed in feet per minute (fpm). The butt welder is also mounted on the column.
What items of a countour machine is containd in the base?
The base contains the saw band drive wheel, motor, and transmission.
What are the speed rages of the transmission?
The transmission has two speed ranges. The low range gives speeds from 50 to 375 fpm, and the high range gives speeds from 200 to 1,500 fpm.
What can the transmission be shifted into?
High, neutral, and low.
What is neutral used for?
Use neutral when you are tracking saw and file bands manually on the guide wheel, and when the machine is not in use.
When do you use low speed?
Use low speed for all sawing operations under 275 fpm.
How do you shift from one range from the other?
To shift from one range to the other, always reduce the speed to below 50 fpm.
With the parts of a saw band what are the teeth?
The teeth are the cutting portions pf the saw band.
With the parts of a saw band what are the gullet?
The opening between the saw band teeth is the gullet. It provides a chip clearance and helps remove the chips from the cut.
With the parts of a saw band what are the width?
The width is the measurement of the band from the tooth tip to the back edge of the band.
With the parts of a saw band what are the gage?
The gage is the thickness the blade measures at the back of the blade. For saws up to 0.500 inchs wide, the gage is usually 0.025 inchs.
With the parts of a saw band what are the pitch?
The pitch is the number of teeth per inch.
With the parts of a saw band what are the set?
The set is the total amount the teeth are offset. The set makes it possible for a saw to cut a kerf or slot wider then the thickness of the band back (gage), providing side clearance.
With the parts of a saw band what are the set pattern?
The set pattern is the pattern of the teeth. There are three set patterns: raker, wave, and straight.
With the parts of a saw band what are the temper?
Temper refers to the hardness of the teeth and the band.
With the parts of a saw band what are the kerf?
The kerf is the slot produced by the saw band.
With the parts of a saw band what are the type?
The type is indicated by the name of the saw band. It refers to the shape and spacing of the saw teeth.
With the saw band how many set pattern are there and what are they?
There are three set patterns: raker, wave, and straight.
When do you use an 8 pitch saw blade?
Large solid sections over 2 inches thick.
When do you use an 10 pitch saw blade?
Soft metals.
When do you use an 12 pitch saw blade?
Medium solid sections, 1/2 inch to 2 inches thick, hardened steels.
When do you use an 14 pitch saw blade?
Heavy-gage materials, general-purpose cutting.
When do you use an 18 pitch saw blade?
Light sections 1/16 to 1/2 inch thick, light-gage and medium-gage sheets and tubing.
When do you use an 22 pitch saw blade?
Very light sections.
When do you use an 24 pitch saw blade?
Very light gage and thin-gage sheets and tubing.
When do you use an 32 pitch saw blade?
Very thin sheets and tubing.
With band saws, what coolant systems is the most common?
The mist coolant system.
On a band saw, what function does the guage to “gap” the guides serve?
The gage permits you to set enough clearance between the guides so the saw band passes smoothly through them without binding or wobbling.
What can be done when the guides become worn?
You can regrind the ends to their original 45 degree angles so they maintain accuracy.
What are the steps for installing a new band on a band saw?
- Open the upper and lower wheel doors.
- Place the right portion of the blade in the table slot, and place it over the upper wheel.
- Ensure it is positioned between the upper and lower sets of inserts.
- Set the “tracking tension by using the handwheel just tight enough to keep the band on the wheels.
- In order to “track” a saw band, rotate the upper wheel band by hand with the transmission in neutral.
What happens if a saw band is over tightened?
Excess tension can cause the bands to break or cause excess wear on the idler and drive wheels.
Narrow bands (less than 3/16 inches) can cut through the rubber on the saw wheels if they’re overtightened.
What distance should you set the guidepost to when operating a band saw?
Ensure the guidepost is within 1/8 to 3/8 inches of the work to provide maximum support for the band.
How wide should the blade be?
Always use the widest and thickest band possible.
What happens if you allow the blade to ride against the work without cutting?
This dulls the saw teeth and may work-harden the metal.
What size do coils of saw bands issue in?
100-foot coils.
How do you weld two sections of band together?
- Cut to length.
- Grind ends square.
- insert in butt welder. Allow 1/64 to 1/32 inch gap.
- Set the tension control switch for the width of the band and the line voltage regulator for the required welding heat.
- Put the flash guard down and press the operating lever to weld the joint; hold it down until the weld has cooled.
- Before releasing the operating lever, loosen the stationary jaw thumbscrew; then, release the band from the movable jaws. Move the band forward to the wide gap annealing position.
- Clamp the band just behind the saw teeth, with the newly welded joint centered between the jaws.
- Press the annealing button until the welded area becomes a dull cherry red. Cool the annealed portion gradually by pressing the annealing button several times during cooling.
- After the band is cool enough to handle, remove it from the jaws and grind the excess weld off both sides. Grind until the welded joint is the same thickness as the band. Use the saw band thickness gage to check for correct thickness.
- After grinding the saw band, temper it to relieve stresses set up during grinding.
- When welding saw bands, always wear safety goggles, since welding causes the band to scale, which can pop off the weld and cause burns.
How often should you oil the transmission?
Oil the transmission monthly. Use a good grade of transmission oil and fill the case to the manufacturer’s recommended level.
How often should you oil the variable-speed pulley?
Oil the variable-speed pulley about once a month with a good grade of spindle oil. Never over-oil this unit because excess oil causes the belt to slip
How often should you oil the drive motor?
Oil the drive motor about once a month with a good grade of machine oil.
How often should you oil the grinder motor?
Oil the grinder motor through the cap fillers on the butt welder panel. A few drops of machine oil about once a month are sufficient.
How often should you oil the moving parts?
Oil moving parts like the slide rod, slide screw, thrust bearings, power feed screw, and speed change screw.
How often should you oil the air pump?
Because this pump has plastic vanes, never lubricate it with oil. If it becomes necessary to lubricate it, pour powdered graphite into the air intake while the pump is operating.
On the horizontal saw, what do you do if the cut begins to drift?
You may need to lower the feed rate, adjust the cutting speed, or adjust the saw band guides.
What PPE must be worn when using the abrasive cutoff saw?
Always wear a face shield.
What are the limitations of a universal punching and shearing machine?
A moderately sized ironworker operates off a 5-horsepower motor and has a punching capacity of 50 tons. If you shear flat stock with a 65,000 psi tensile strength, you can cut ⅝-inch thick material, but the width is limited to 5 inches. The same material that is ¼-inch thick can be cut in widths up to 10 inches. Keep in mind the tensile strength of the material. Higher tensile strength materials reduce the capacity of the machine.
What are the steps for operating a punch?
- Depress the foot pedal and slowly bring the punch ram to within ½ inch of the die to ensure they align properly. 2. Position the stripper and adjust it so it is no more than ⅛ inch above the workpiece top surface. 3. Jog the machine several times to ensure the punch clears the stripper. 4. Oil the punch and die before performing the operation. 5. Operate the punch, oiling the punch and die after every 5 to 10 strokes. 6. Punch full and complete holes, not partial holes. Partial holes could cause the punch to press against the die and break. 7. Keep at least 1/16 inch material thickness between the hole and the material edge to keep the workpiece from deforming.
What material can the rod shear accommodate?
The rod shear guide can accommodate up to 1⅜-inch round or 1¼-inch square material.
When do you use sand as a media blasting material?
It is used mainly on hard materials such as iron or steel.
When do you use plastic as a media blasting material?
Paint removal.
When do you use Glass as a media blasting material?
Glass beads can be used on a variety of materials. They are cost-effective and respond well to velocity changes based on blasting machine nozzle pressure. Glass beads are not as abrasive as sand, so you can use them on softer materials.
When do you use shot as a media blasting material?
Shot has about five times the abrasive life of sand and about 10 times the abrasive life of glass beads. It’s available in screen gages ranging in size from 0.0165 to 0.187 inch. Shot can be a ferrous material (i.e., cast steel and chilled iron), or it can be nonferrous (i.e., as Al). Al shot is very effective for cleaning nonferrous metals (i.e., brass castings, Zinc (Zn) and Al dies). Shot is less damaging to equipment
When do you use organic abrasives as a media blasting material?
removing light carbon scale.
What factors determine the strike angle?
Strike angle is the angle at which the media strikes the workpiece surface. It’s a critical factor, since an incorrect strike can damage work surfaces or it can make the task take longer. The range for a strike angle for most materials is from 15° to 80°; the actual angle depends on the type of material being blasted (fig. 3–22).
What is the surface distance to use?
12-18 inches.
How do you prepare a surface for blasting?
Thoroughly clean the surface to remove grease, oil, fluids, and dirt.
What is your goal when you construct a drawing?
Complete the drawing accurately and quickly.
What three things can you do to make drawing more comfortable and improve your work?
Arrange your equipment systematically for efficiency, place items within reach, and keep your equipment clean.
What are the basic equipment items used for drafting?
Drawing board, T-square, set of triangles, scales, pencils, protractor, erasers, curves, and a set of drafting instruments.
What should you use to sharpen the point of a pencil used for mechanical drawing?
Sand paper or a pencil pointer.
What erasers are most preferred for drafting use?
Art gum and pink pearl.
What are the two most common types of scales used in drafting?
Engineer’s and architect’s.
As a minimum, what instruments should your drawing set include?
One pair of large dividers, one large compass, one small bow compass, one small bow divider, compass leads and spare points.
What instrument do you use to transfer measurements and distances?
Dividers.
What are dimension lines?
Fine solid black lines terminated at each end by an arrowhead. They indicate the dimensions of a space.
If you can’t immediately identify a dimension as a diameter, what should you do?
Place the abbreviation DIA after the numeral.
What are the identifying symbols for location, size, and radius?
L-location, S-size, R-radius.
What are the rules for dimensioning a drawing?
Place dimensions that apply to related views between the views whenever possible. Don’t place dimensions directly on an object. Place dimensions that apply to more than one view on the view that most clearly shows the feature being dimensioned. Don’t place dimensions on hidden edges. Avoid unnecessary duplication of dimensions. Locate dimensions for the entire drawing so that they all read from the bottom. Place small dimensions near the object, and larger objects farther away from the object.
Define chamfer, countersink and counterbore.
A chamfer is a beveled external or internal edge. A countersink is a conical depression to accommodate a screw head; a counterbore is a recess at the top of a drilled hole.
How do you dimension slots in a drawing?
For slots with rounded ends, give the overall length and width of the slot plus the radii.
What four information items do you include when dimensioning threads?
The diameter of the thread, the TPI, the thread series, and the class of fit.
What is tolerance?
The difference between the allowable minimum and the allowable maximum dimension.
What is allowance?
The intentional difference in dimensions of mating parts.
What’s the difference between clearance allowance and interference allowance?
Clearance allowance permits movement between mating parts when they’re assembled. Interference allowance is the opposite of clearance allowance.
Define a welding symbol.
Welding symbols give all of the information you need for a print: reference line, arrow, basic weld symbol, dimensions, supplementary symbols, tail, specification and process.
Define a weld symbol.
Weld symbols give the type of weld and its shape or contour.
Define vertical lines tool.
The vertical lines tool creates an unbounded (without termination points) vertical line through the point you choose.
Define connected lines tool.
Lines that are defined by endpoints, but the last endpoint entered will be the start point of the next line.
Define trim or extend tool.
Trim or extend tool changes the length of a line or arc.
What is the function of a grid when used in CAD drawings?
Overlays the display screen with a grid pattern of any desired size. It is used as a guide to help construct geometry accurately.
What are the four main benefits of CAD?
Speed, quality, storage, and editing.
What information will you find in the title block of a blueprint?
Material, heat treatment required, specified tolerances, finish notes, drawing scale, print identification, and bill of materials.
How are notes positioned on a print?
So that they read from left to right and parallel to the bottom of the print.
What are the three common types of notes? Describe them.
Local notes apply directly to a particular part of a drawing. General notes apply to the overall drawing in general. Indexed notes apply to specific areas on the drawing, cross referenced to a parts list on the print.
What is a TO working drawing?
Guides you in the manufacture of items.
What is a TO assembly drawing?
Contains partial or complete assemblies, instead of one or two parts. They don’t have specific dimensions, except overall dimensions, center distance dimensions, and dimensions relating to other parts or assemblies.
Describe unit assembly drawing, maintenance assembly drawing, and exploded drawing.
Unit assembly drawing shows a completely assembled unit, you can see all parts of the unit, may have a cutaway to reveal internal parts or surfaces. A maintenance assembly drawing shows units in the process of assembly. Exploded drawings show the relationship of parts in a unit, not assembled, but as if the unit was “exploded” without the parts losing their relative positions.
What are the layout tools you’ll most likely need for welding fabrication layout?
Soapstone, a square, a straightedge, and a tape measure.
What happens if you use too much layout dye?
It will flake, and create ragged, uneven lines when you scribe.
What other use can you find for soapstone in welding operations?
Write the word HOT on the material, and give the time, too. This will help keep your co-workers safe by letting them know not to touch the work.
What tool material is known to be erratic when heat treated?
Plain carbon steels.
High-speed tool steels are valuable in tool manufacturing for what reason?
They retain hardness and strength at high operating temperatures.
What tool material routinely performs beyond the limits of tool steels and is suitable for hard abrasive materials and hard alloys?
Nonferrous tool materials (tungsten, tantalum, titanium, columbium, cobalt).
What are five defects found in low grade steel?
Seams, laminations, blowholes, erratic grain size, uneven tensile strength.
What is the main cause of tool deflection?
Dull tooling.
What is the best method to keep tool thermal expansion to a minimum?
Keep cutting tools sharp and use lots of coolant.
What are two areas you should consider as you develop a plan to machine parts?
Use a materials and parts list. Decide on what hand and measuring tools are available and how to get them, and decide whether you can improvise.
If you’re going to machine holes in a part, and the holes size and location are not critical, what machine would you choose?
Use a drill press.
What’s the difference between a jig and a fixture?
Jigs hold, support, and locate a workpiece while guiding a cutting tool. Fixtures hold, support, and locate a workpiece in relation to a cutting tool.
List the items to consider before you build a jig or a fixture.
Find points that allow positive location. Locating points should hold a workpiece in the same location every time. Consider the equipment and the clamping arrangement. Make sure there’s enough chip clearance.
What are the two general classes of jigs?
Drilling and boring.
What type of jig is used for limited production?
Template.
What are the limitations of using auxiliary vise jaws as fixtures?
The diameter of the stock, the working size of the vise, and the depth of the V cut.
What are the four common types of fixture body construction?
Built up construction, welded construction, cast construction, solid construction.
Describe the 3–2–1 principle of locating.
Use three locators on the base for stability, use two locators on the vertical side next to one of the long sides to prevent rotation and linear movement, use one locator on the vertical side next to an end to complete the location of the part.
What’s blanking?
Blanking means cutting out a part with a punch or die.
What’s the difference between piercing and blanking?
During piercing, the punched out material is the scrap, while during blanking, the punched out piece is the workpiece.
What die would you select to form aircraft structural parts?
A bending or forming die.
What’s another name for a loose fit?
A clearance fit.
What class of fit is used for machines running at higher speeds and heavy journal pressure?
RC5 and RC6.
For what purpose is LC fits used?
For stationary fits where parts can be freely assembled and disassembled.
What fit will you select to maintain accuracy, but permit a small amount of clearance or interference?
Locational transitional.
What fit do you select for parts that need rigidity and extreme location accuracy?
Locational interference.
What are some methods of chilling parts for interference fits?
Placing them in a freezer, packing them in dry ice, spraying with CO2, or submerging in liquid nitrogen.
What are the general rules for determining the amount of interference fit on parts?
Allow approximately 0.0015″ per inch of diameter of the bored part. The amount of interference decreases as the part diameter increases. The wall thickness of a part effects interference.
What is the main purpose of lubrication?
To reduce friction between parts.
What is kinetic friction?
Friction between a stationary and a moving surface, or friction between two moving surfaces.
What is static friction?
Friction between two surfaces at rest.
Explain cohesion and adhesion in terms of fluid friction.
Cohesion is the attraction between the molecules of a substance that tends to hold the substance together (the molecules of the fluid try to stay together). Adhesion is the attraction between molecules that tends to cause unlike surfaces to stick together (the oil tries to adhere to the tube or pipe lining).
Besides permitting one surface to slide over another, what other benefit does a lubricant provide?
It helps carry heat away from the bearing surfaces.
Explain the difference between high-viscosity oil and low-viscosity oil.
High-viscosity oil flows slowly while low-viscosity oil flows quickly.
What grade of grease do you select for slow machine speeds with heavy pressure?
Hard grease.
List the limitations of dry film lubricants.
They cannot carry heat away from the operating area, don’t replenish themselves like greases, and don’t adhere to the material surface the way greases do.
What is the main purpose of a coolant?
To carry away cutting tool heat.
What is the purpose of a cutting fluid?
To reduce cutting forces, ease machining, and lubricate materials as they are machined.
What important item must you consider if you’re selecting a cutting fluid for Al?
Al chemically reacts with some cutting fluids.
In a machining operation where your workpiece is made of Mg, which cutting oil do you select?
One that doesn’t contain any water.
What is the disadvantage of using compressed air as a coolant?
It does little to prevent friction and cutter tip breakdown.
What advantage does the jet cooling method have over the other cooling methods?
It’s a more effective method of cooling because it forces coolant onto the tool and part contact area. This reduces cutting tool temperature and prolongs cutting tool life
What item on the saw band permits it to cut a kerf wider than the gage?
The set.
On the contour machine, where are the upper and lower guide blocks mounted?
The upper guide block is secured to the lower end of the guidepost; the lower guide block is secured to a keeper block under the table.
How is the contour machine upper wheel adjusted to permit the band to track properly?
Loosen the tilt locknut and rotate the upper wheel by hand. Use the tilt screw to tilt the wheel until the back edge of the saw band contacts the thrust roller on the guide block and the band tracks lightly on the guide roller; then, retighten the tilt locknut.
To select the correct speed for a sawing operation, what two things must you consider?
The type and thickness of the material you’re cutting.
How does the recommended speed for sawing titanium and Monel differ from that for most other nonferrous metals? Give the comparable speeds.
The recommended speed for titanium and Monel is much slower (90 to 125 fpm) than for most nonferrous metals (700 to 1,500 fpm).
Why should the sawing feed pressure be greater on titanium than on most other metals?
Because titanium does not dissipate heat quickly.
How can you help prevent injury to your hands when you apply feed pressure to the work by hand when sawing or filing on the contour machine?
By using a pusher block.
How is the lower saw guide affected when the table is tilted more than 20°?
Mount the saw guide in the lower mounting holes in the keeper block.
How do you check the angle of the table, other than by using the graduated plates below the table?
Measure the angle formed by the guidepost and the table top with a protractor head and blade.
In what way do you cut a saw band prior to welding?
Through the gullets, from the back toward the teeth.
What safety precaution must you observe during a welding process?
Wear safety goggles.
What is the purpose of the rip fence?
To cut stock so its sides are parallel.
Explain the techniques for lubricating the grinder motor. How often do you lubricate it?
Put a few drops of oil into the cap fillers on the welder panel; about once a month is sufficient.
With what do you lubricate the air pump?
Only with powdered graphite that is put into the air intake.
Describe the techniques for correcting the problem of worn and grooved tires on the upper and lower wheels.
Remove them, turn them inside out, and reinstall them. If the tires are badly worn, replace them.
What is the function or purpose of power cutoff tools?
To make straight, vertical cuts.
Why are the saw bands on horizontal band saws wider and heavier than those used on the contour machine?
To permit heavier cutting forces.
What item keeps the saw band cutting efficiently without excessive wear?
The feed adjustment.
How do you set band guides for cutting?
They must be as close to the work as possible to keep the band from flexing, twisting, and binding.
When using an abrasive cutoff saw, why do you support long workpieces?
To keep them from twisting in the machine vise or falling and causing injury or damage to the machine.
What operations can you accomplish with the ironworker?
Piercing, shearing, notching, coping, and bending.
What determines an ironworker’s capacity?
The pressure in psi of the cutting stroke.
What must you adjust prior to operating the ironworker? Why?
The hold-downs; to prevent kickback.
How often should you lubricate the blade when performing cutting operations?
Every 10 to 15 strokes.
What is the limitation on material thickness for blasting using silica sand abrasive?
Don’t blast material thinner than 0.0625 inch.
Which abrasive is highly effective for paint removal?
PMB.
What is the disadvantage of using glass beads as a blasting medium?
They fracture after several uses, which makes them more abrasive, but less effective.
Where are you most likely to see shot used as a blasting medium?
In peening operations.
Which type of abrasive works best for removing scale from intricate workpieces?
Organic.
At what point do you replace the nozzle outlet on a media blasting machine?
When it’s worn to 1½ times its original size.
What is the correct pressure range for media blasting?
15 to 60 psi.
Why is surface distance critical? What is the correct distance?
If you hold the nozzle too close, it can damage the workpiece; too far away can slow down the cleaning process. The correct distance is 12 to 18 inches from the material surface.
Define “dwell.” What can happen to material surfaces if you dwell too long on an area?
The length of time you blast in one spot on a workpiece; it can cause the surface to develop stress concentrations and warp, and, on softer materials, it causes the abrasive to eat away the material surface.
Why do you remove fluids from material surfaces before blasting?
Fluids can impregnate the material surface and contaminate the blasting media.
Why is correct masking an important step of surface preparation?
It keeps the abrasive material from intruding into interior surfaces, and damaging or contaminating equipment.
How do you remove the blasting media after you’ve completed the blasting process?
Vacuum the workpiece to remove the abrasives; use compressed air or water as an alternative.
When clamping workpieces, how do you protect finished surfaces?
Use metal shims.
What is the most common work-holding device for a drill press?
The drill press vise.
Describe the radial drill press.
The radial drill press is capable of drilling large objects and the table is designed to allow many variations to the way you mount and secure objects. The table can be tilted 90°; it has two mounting surfaces—the top surface and an adjacent surface 90° to the top surface. Each mounting surface has T-slots to permit the use of tie-down bolts, clamps, straps, V-blocks, or angle plates. Before you mount anything on the radial drill press table, ensure the graduated scale is “zeroed” so the table is square to the machine spindle.
What is the formula for determining spindle speed?
RPM = 4 X CFS / DIA.
When pilot drilling, how do you determine the next size bit to use?
A pilot drill is a drill slightly larger than the thickness of the web of the next drill to be used (fig. 4–8).
When using a transfer punch what size should you first drill to?
1/32”.
When installing a radial arm drill press what should you ensure?
the radial arm can move freely in a 360 degree arc swing.
How much pressure does a hydraulic press have?
Typical shop hydraulic presses have between 5 and 50 tons of pressure available.
When drilling, why do you allow some movement or “float” between the twist drill and the workpiece?
Allows the center punch mark to align the workpiece to the drill as it starts to drill the hole.
How can you prevent work from climbing up the drill bit as it breaks through the lower work surface?
By reducing the feed pressure.
Why does a large drill bit require a slower rpm than a small one, even though the type of metal to be drilled is the same?
A change in drill diameter results in a change of circumference, you must change the rpm to get the same desired CFS.
You must drill a ½-inch hole in a piece of stainless steel. You select a CFS of 35. What rpm would give you the required CFS? Use the proper formula to arrive at your answer.
280.
When do you not use a center drill to start a hole?
For smaller drill presses if the workpiece cannot float on the table and align under the spindle because any misalignment of the center-drilled hole is difficult to correct.
Identify the safety practices to follow during drill press operation.
Always wear safety glasses, button or roll long shirt sleeves up past your elbows, or remove your shirt.
What safety precaution do you take when you stop the spindle to put a different bit in the drill chuck?
Allow the spindle to stop by itself; avoid stopping the chuck by grasping it with your hand.
What is the safe way to remove chips from a drill press operation?
Stop the spindle; then, remove the chips with a brush or rag.
How can you prevent a drill bit from producing dangerously long and stringy chips?
By interrupting the feed regularly during the drilling operation to break the chips.
What two things must you ensure when installing a drill press?
Level the column to the floor, and bolt the machine securely in place.
What technique do you use when lubricating the drill press?
Start at one point and lubricate all points progressively around the machine.
How can you help prevent the arm of a radial drill press from seizing on the column when you raise or lower the arm?
Wipe the dirt and grit from the column and apply a fresh oil film before raising or lowering the arm.
List six operations where you can use a mechanical arbor press.
Remove shafts from gears and pulleys; remove bearings or bushings from shafts; assemble parts such as bushings, pins, and shafts; straighten small shafts; broach keyways; dimple sheet metal.
What is the advantage of using a mechanical arbor press for broaching?
It is sensitive enough to “feel” the pressure, which can keep you from overpressing a part.
What two components of the hydraulic press are used to create the pressure needed to perform press operations?
A hydraulic cylinder and pump.
What items should you consider before you begin any press operations?
The interference fit between the mating parts, corrosion, marred edges, overlooked fasteners, and the mass of the part.
What precautions must you take when operating a press to prevent damage to the equipment?
Adequately support the work; place the ram in contact with the work for accurate location and alignment; use a soft metal shim between the press ram and work to protect the work surface; use a lubricant to prevent seizing; and if you’re using too much pressure, release it and double-check to find the cause of the bind.
If you were required to press a 5¼-inch shaft into a gear housing, how much pressure would you exert on the shaft?
36.75 to 52.50 tons maximum.
What are the maintenance requirements for presses?
Check machine forms and the manufacturer’s guidance for maintenance requirements. Maintenance is primarily limited to lubricating pivot points.
What is the maximum pressure that you should use with a hydraulic press?
As a guideline for force-fitting a cylindrical shaft, the maximum pressure in tons should not exceed 7 to 10 times the shaft’s diameter in inches.
Referring to figure 5–1; use the grinding wheel identification number “50–C80–E10–S32” and identify what each number or letter represents. 50
Manufacturer’s symbol for that abrasive.
Referring to figure 5–1; use the grinding wheel identification number “50–C80–E10–S32” and identify what each number or letter represents. C
Silicon carbide abrasive.
Referring to figure 5–1; use the grinding wheel identification number “50–C80–E10–S32” and identify what each number or letter represents. 80
Very fine grain.
Referring to figure 5–1; use the grinding wheel identification number “50–C80–E10–S32” and identify what each number or letter represents. E
Soft grade.
Referring to figure 5–1; use the grinding wheel identification number “50–C80–E10–S32” and identify what each number or letter represents. 10
Dense structure.
Referring to figure 5–1; use the grinding wheel identification number “50–C80–E10–S32” and identify what each number or letter represents. S
Silicate bond.
Referring to figure 5–1; use the grinding wheel identification number “50–C80–E10–S32” and identify what each number or letter represents. 32
Manufacturer’s record symbol.
What part of the grinding wheel removes the metal while grinding? Explain this process.
Abrasives remove material from the surface of a workpiece. Each abrasive grain acts as a separate cutting tool, removing a small metal chip as it passes over the surface of the workpiece.
What are the two types of abrasives?
Natural and manufactured (artificial).
What is one advantage manufactured abrasives have over natural abrasives?
Manufacturers can control grain size, grain shape, and purity.
Which abrasive is the most common abrasive available?
Al oxide.
What is the main difference between silicon carbide and Al oxide abrasives?
It is harder and tougher, and fractures more easily than Al oxide.
Which type of abrasive is used to grind the toughest and hardest materials?
Industrial diamond.
What factors determine the grinding wheel grade you will select for a particular job?
The kind of material you want to grind, the amount of stock to remove, the accuracy and finish required, the contact area between the wheel and the work, the nature of the operation, the work and wheel speed.
What do you do when you receive a new wheel or remove one from storage?
Inspect it closely for damage and cracks.
How do you check a wheel for cracks?
Tap it gently with a light nonmetallic instrument, such as the handle of a screwdriver.
How can you tell if a wheel is cracked?
A cracked wheel is readily identified because of its “dead” sound.
How do you balance a grinding wheel?
By shifting the position of the balance weights, which are located inside a circular groove cut in the wheel mount bushing.
What do you need to do after mounting a new wheel on your grinder?
Stand to one side and let it run at full operating speed for at least one minute before using it.
What does dressing a grinding wheel improve?
Improves the cutting action of the wheel.
Which dressing tool is the most efficient for truing precision grinding wheels?
The diamond dresser.
Where should you store all grinding wheels regardless of type?
In a dry place.
What is the procedure for sharpening a drill bit with a pedestal grinder?
Position your hand on the tool rest; use your fingers as a pivot and push down on the shank of the drill bit as you “roll” the drill across the face of the wheel; keep the shank lower than the cutting edge.
Why is it important not to raise the shank of the drill bit higher than the cutting edge while sharpening it?
You could grind a negative relief angle on the cutting edge.
What happens with repeated sharpening of a drill bit?
You shorten the drill bit and the web thickness increases, which lengthens the chisel edge.
What do you use to check drill point angles when sharpening them?
Drill point gage or with the protractor head and blade.
What is the maximum allowable distance between the tool rest and the grinding wheel? Why is it important to check and adjust it often?
⅛ inch. The grinding wheel wears as you use it and the gap increases.
What malfunction can result if dirt is allowed to build up on a grinding machine?
It can get into the bearings and electrical connections and cause a breakdown.
What preventive maintenance practices are followed concerning lubrication?
Refer to the lubrication schedule in the TO or manufacturer’s publication and follow it.
List four safety factors you must follow when using a belt sander.
(1) Always wear eye protection when belt-grinding. (2) Never grind on the “up” side of an abrasive belt (with the belt rotating toward you). (3) Bring sharp corners and edges into contact with the belt lightly to prevent tearing the belt. (4) Have a small quench tank or container of water available to cool the part.
What factors determine the size of a belt sander?
The horsepower of the motor and the size of the sanding belt.
What is the purpose of the backup platen?
Provides a large surface area behind the sanding belt for flat grinding.
Briefly explain loose belt grinding.
Allows the operator to sand intricate shapes by using the flexibility of the sanding belt to wrap around contours.
Why is it important to prevent movement of the belt tracking knob when the machine is off?
If adjustments are made with the machine off, when you power up the machine, the belt can quickly shift position, possibly causing injury to you or others or damage to the machine.
How does pure waterjet and abrasive waterjet cutters differ?
With a pure waterjet, the supersonic stream erodes the material. With the abrasive waterjet, the waterjet stream accelerates abrasive particles; those particles, not the water, erode the material.
Which machine is more suited for cutting hard materials?
The abrasive waterjet.
Which two styles of machine dominate the industry?
Mid-rail gantry and cantilever.
What two types of pumps are used in waterjet applications?
Direct-drive-based and an intensifier-based pump.
What is the most common abrasive used?
Garnet.
How is the geometry created for more complex parts?
By using CAD software.
How do most machines calculate feed rate?
It is calculated from the material type, the thickness, and what your desired finish is.
How does the geometry of the part affect the cutting speed?
Parts with lots of holes and sharp corners cut much slower than simpler shapes.
What can you do if you have dirty or hard water?
Maintain everything more often, or purchase a good water softener or filtration system.
What can happen if you get dirt in the high-pressure plumbing?
They become bullets that crack the jewel.
What should you do after rebuilding something up-stream of the nozzle?
Remove the nozzle and flush the lines with low pressure prior to putting the nozzle back on.
How can you minimize uneven wear of the mixing tube?
By rotating the mixing tube once in a while.
