MET 1110
State three advantages of broaching.
- Machining almost any irregular shape is possible, providing it is parallel to the broach axis. - It is rapid; the entire machining process is usually completed in one pass. - Roughing and finishing cuts are generally combined in the same operation. - A variety of forms, either internal or external, may be cut simultaneously and the entire width of a surface may be machined in one pass, thus eliminating the need for a machining operation.
Name two methods by which heat is created during machining.
- The plastic deformation occurring in the metal during the process of forming a chip - The friction created by the chips sliding along the cutting-tool face
State 5 reasons why granite plates are better than cast-iron plates.
-Do not become burred -Do not rust -Not affected by temperature change -Do not have internal stresses and therefore will not warp or distort -Are nonmagnetic -Can be used for checking near grinding machines, since abrasive particles will not embed in the surface -Cheaper than a similar-size cast-iron plate
Squares- List four main parts of a combination set.
-a steel rule -square head -bevel protractor -center head.
Name five advantages of ceramic tools.
1. High-speed, single-point turning, boring, and facing operations, with continuous cutting action 2. Finishing operations on ferrous and nonferrous materials 3. Light, interrupted finishing cuts on steel or cast iron; heavy, interrupted cuts on cast iron only if there is adequate rigidity in the machine and tool 4. Machining castings when other tools break down because of the abrasive action of sand, inclusions, or hard scale 5. Cutting hard steels up to a hardness of Rockwell c 66, which previously could be machined only by grinding 6. Any operation in which size and finish of the part must be controlled and in which previous tools have not proved satisfactory
List four factors that affect production rates.
1. Inadequate horsepower, which limits the metal- removal rate 2. Surface finish requirements, which may limit the feed rate 3. Machine rigidity, which may not be sufficient to withstand cutting forces, feed rate, and depth of cut 4. Rigidity of the part being machined, which may limit the depth of cut
What are the advantages of a radial drilling machine?
1. Larger and heavier work may be machined. 2. The drilling head may be easily raised or lowered to accommodate various heights of work. 3. The drilling head may be moved rapidly to any desired location while the workpiece remains clamped in one position; this feature permits greater production. 4. The machine has more power; thus, larger cutting tools can be used. 5. On universal models, the head may be swiveled so that holes can be drilled on an angle.
How does the addition of titanium carbide affect the cutting tool?
1. The addition of titanium carbide provides resistance to tool cratering. The higher the titanium content, the greater is the resistance to cratering. 2. As the titanium carbide content is increased, the toughness of the tool is decreased. 3. As the titanium carbide content is increased, the abrasive wear resistance at the cutting edge is lowered. 4. Tantalum carbide additions have effects similar to tungsten carbide on the resistance to cratering and strength. 5. Tantalum carbide gives good crater resistance without affecting the abrasive wear resistance. 6. The addition of tantalum carbide increases the tool's resistance to deformation.
List four main advantages of diamond cutting tools.
1. They can be operated at high cutting speeds, and production can be increased to 10 to 15 times that of other cutting tools. 2. Surface finishes of 5 min. (0.127 m) or less can be obtained easily. In many cases, the necessity of finishing operations on the workpiece is eliminated. 3. They are very hard and resist abrasion. Much longer runs are therefore possible on abrasive materials. 4. Closer tolerance work can be produced with diamond-tipped cutting tools. 5. Minute cuts, as low as .0005 in. (0.012 mm) deep, can be taken from the inside or outside diameter. 6. Metallic particles do not build up
Describe a snap gauge ( Thread plug and Ring gauges)
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Screw threads- What dimension of the thread is indicated on a screw thread micrometer reading
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How is a tapered-shank drill removed from a drill press spindle?
A flat, wedge-shaped tool called a drill drift is used to remove tapered-shank drills or accessories from the drill press spindle.
Describe the principle of electro-band machining.
A low-voltage, high-amperage current is fed into the saw blade. The workpiece is connected to the opposite pole of the circuit. When the work comes close to the fast-moving band [6000 sf/min (1827 m/min)], a continuous electric spark passes from the knife edge of the saw to the work. This arc acts on the material and disintegrates it. The blade does not touch the work. Coolant is flooded onto the cutting area to prevent damage to the material by the heat created. Power feed must be used in this type of machining operations.
What is the purpose of a hand reamer?
A tool used to finish drilled holes accurately and provide a good finish.
Why must the upper saw guide be close to the top of the work?
Allow .001- to .002-in. (0.02- to 0.5-mm) clearance to ensure that the blade will not bind.
Why should holes that are to be tapped be countersunk?
An 82° countersink is used to enlarge the top of a hole so that it will accommodate a flat-head machine screw.
Why is it important that friction between the chip and the tool be kept to a minimum?
As the coefficient of friction increases, there is a greater possibility of a built-up edge forming on the cutting edge. The larger the built-up edge, the more friction is created, which results in the breakdown of the cutting edge and poor surface finish.
What may occur if too slow a cutting speed is used?
At very low speeds, a built-up edge may occur on the cutting tool, requiring tool changes.
What is formed on the surface of a part during the black-oxide process.
Black iron oxide = magnetite
Why is a properly sized box wrench preferred to other types of wrenches?
Box end has 12 precisely cut notches around the inside face, these notches tightly grip the nut. The wrench cannot slip when the proper size is used.
How should the work be fed into a revolving saw?
Carefully feed the workpiece into the saw. Do not use too much force.
What is a cermet cutting tool?
Cermets are cutting tools made of various ceramic and metallic combinations.
Why is it important that work be clamped properly for any machining operation?
Clamping stresses should not be great enough to cause springing or distortion of the workpiece.
Why is tumbling an important production process?
Cleaning, polishing, and removing sharp corners and burrs from metal parts. Nice Finish :)
What is the principle of coordinate measurement?
Coordinate measurement is a method used to speed up layout, machining, and inspection by having all measurements dimensioned from three rectangular coordinates (surfaces of the workpiece): X, Y, and Z
Describe briefly how each of the following chip types is produced: Discontinuous - Continuous -
Discontinuous - The metal ahead of the cut will compress then break off Continuous - Comes from high-speed cutting tool or carbide tool that cuts more precisely, metal ahead won't compress and instead just peels down the cutting line
List four systems of drill sizes and give the range of each.
Drill sizes are designated under four systems: fractional, number, letter, and millimeter (metric) sizes. 1. The fractional size drills range from 1⁄64 to 4 in., varying in steps of 1⁄64 in. from one size to the next. 2. The number size drills range from #1, measuring .228 in., to #97, which measures .0059 in. 3. The letter size drills range from A to Z. Letter-A drill is the smallest in the set (.234 in.) and Z is the largest (.413 in.). 4. Millimeter (metric) drills are produced in a wide variety of sizes. Miniature metric drills range from 0.04 to 0.09 mm, in steps of 0.01 mm. Straight- shank standard metric drills are available in sizes from 0.5 to 20 mm. Taper-shank metric drills are manufactured in sizes from 8 up to 80 mm.
Define drilling, Boring, and Reaming.
Drilling: producing a hole by removing metal from a solid mass using a cutting tool called a twist drill. Boring: truing and enlarging a hole by means of a single-point cutting tool, which is usually held in a boring bar. Reaming: sizing and producing a smooth, round hole from a previously drilled or bored hole with the use of a cutting tool having several cutting edges.
What is the effect of: Drills with unequal angles on the cutting lips? Drills with cutting lips of unequal length?
Drills with unequal angles on the cutting lips? The drill will cut an oversize hole because one lip will do more cutting than the other Drills with cutting lips of unequal length? Force the drill point off center, causing one lip to do more cutting than the other and producing an oversize hole
What problems generally result from the use of excessive speed and excessive feed?
EXCESSIVE SPEED WILL CAUSE WEAR AT OUTER CORNERS OF DRILL; THIS PERMITS FEWER REGRINDS OF DRILL DUE TO AMOUNT OF STOCK TO BE REMOVED IN RECONDITIONING. DISCOLORATION IS WARNING SIGN OF EXCESS SPEED. EXCESSIVE FEED SETS UP ABNORMAL END THRUST, WHICH CAUSES BREAKDOWN OF CHISEL POINT AND CUTTING LIPS. FAILURE INDUCED BY THIS CAUSE WILL BE BROKEN OR SPLIT DRILL.
Why are various drill points and clearances used for drilling operations?
Efficient drilling of the wide variety of materials used by industry requires a great variety of drill points. The most important factors determining the size of the drilled hole are the characteristics of the drill point.
What purpose do fixed gauges serve in industry
Fixed gauges provide quick accurate measurement during inspection work
What is the general rule for the amount of material left in a hole for machine reaming?
For holes up to .500-in. diameter, allow .015 in. for reaming. For holes over .500-in. diameter, allow .030 in. for reaming.
Of what material are saw blades made?
High-speed tungsten and high-speed molybdenum steel
State the purpose of a.) hook rules and b.) decimal rules
Hook rules "hook" on the edges to make accurate measurements. Decimal rules provide a simple and accurate form of measurement.
Why should two teeth of a saw blade be in contact with the work at all time?
If fewer than two teeth are in contact with the work, the work can be caught in the tooth space (gullet), which will cause the teeth of the blade to strip or break.
Why should a layout be as simple as possible?
If the part does not have to be precise, time should not be spent making a precision layout.
Which factor increase causes the greatest reduction in cutting tool life?
Increasing the cutting speed by 50% reduces tool life by 90%.
Describe the cutting action of a broach.
It is forced through a hole in the workpiece to reproduce its shape in the metal.
What is the purpose of a reamer?
It is used to accurately size and smooth a hole that has been previously drilled or bored.
Why is pure aluminum more difficult to machine than most aluminum alloys?
It produces long, stringy chips and is much harder on the cutting tool because of its abrasive nature.
Lapping- Why must the lap be softer than the workpiece?
Lapping is used to finish workpieces, if the lap is harder than the piece, it could start cutting away the material.
What are the three factors that influence cutting tool life?
MRR: cutting speed, feed rate, and depth of cut
Describe machinability
Machinability describes the ease or difficulty with which a metal can be machined. Such factors as cutting-tool life, surface finish produced, and power required must be considered.
Formulas for r/min
Metric: r/min = CS(in m)/(pi x D) Inch: r/min = CS(in ft/min) x 12/(pi x D)
Explain the procedure for setting an inside caliper to the size of a hole.
Place one end of the caliper on one edge and then adjust the other end of the caliper until a resistance is felt.
What advantage do vice grips have over other types of pliers?
Provide extremely high gripping power because of the adjustable lever action. The screw in the handle allows adjustment to various sizes.
What is the difference between spot-facing, and counterboring?
Spot-facing: smoothing and squaring the surface around a hole to provide a seat for the head of a cap screw or a nut. A boring bar, with a pilot section on the end to fit into the existing hole, is generally fitted with a double-edged cutting tool. Counterboring: enlarging the top of a previously drilled hole to a given depth to provide a square shoulder for the head of a bolt or cap screw.
Name 4 types of steel rules used in machine shop work.
Spring tempered, flexible, narrow, and hook
Explain why present-day standards for surface finish are very important to industry.
Surface finishes ensure the proper functioning and long life of machine parts.
What is the purpose of a surface plate
Surface plates are machined to be extremely flat and level, they are used for accurate inspection work.
Why are beveled-edge squares used in inspection work
The beveled edge allows the rule to make line contact with the work, for an accurate check
Explain how you would know when the work is the same size as the caliper setting.
The caliper should slide over the work by its own weight
Which is the most desirable type of chip? Give reasons for your answer.
The continuous ribbon chip is considered ideal for efficient cutting action because it results in better surface finishes.
What two factors must be considered when arriving at the total cost of a part?
The cost of using the cutting tool and the price of the cutting tool.
Why is it important not to quench carbide tools?
The shock of quenching carbide tools creates heat checks and results in rapid tool failure.
Why is it good practice to start each hole with a center hole?
The small point of the center drill will pick up a center-punch mark accurately; the center- drilled hole will provide a guide for the drill to follow.
What is the purpose of spotting a hole before drilling?
The small point on the center drill will accurately follow the center-punch mark and provide a guide for the larger drill which will be used.
Explain the difference between cutting speed and r/min.
The speed of a twist drill is generally referred to as cutting speed, surface speed, or peripheral speed. It is the distance that a point on the circumference of a drill will travel in 1 min. The number of revolutions of the drill necessary to attain the proper cutting speed for the metal being machined is called the revolutions per minute.
In what direction should the teeth of a saw blade point?
The teeth should point in the direction of saw travel or toward the motor end of the machine.
Describe the principle of friction sawing.
The tremendous heat generated by friction brings the metal immediately ahead of the saw teeth to a plastic state, and the teeth easily remove the softened metal.
State the advantages of carbide-tipped reamers.
These reamers resist abrasion and maintain sharp cutting edges even at high temperatures, and carbide-tipped reamers outlast high-speed steel reamers.
What is the purpose of the roller guide brackets?
They provide rigidity for a section of the blade and can be adjusted to accommodate various widths of material. They should be adjusted to just clear the width of the work being cut.
Name four ways in which cutting fluid assist the machining of metals.
They reduce the temperature of the cutting action. They reduce the friction of the chips sliding along the tool face. They decrease tool wear and increase tool life. Make it possible to cut metals at higher rates of speed.
Define tap drill size
This is the drill size that would leave the proper amount of material in the hole for a tap to cut a thread. The tap drill is always smaller than the tap and leaves enough material in the hole for the tap to produce 75% of a full thread.
For what purpose are threading dies used?
Threading dies are used to cut external threads on round work.
What is the purpose of a cutting fluid?
To provide both cooling and lubrication.
Why are surface treatments used on metals?
To resist wear, electrolytic decomposition, and corrosive wear due to weather.
What may happen if too fast of a saw speed is used?
Too fast a blade speed or excessive feeding pressure will dull the saw teeth quickly and cause an inaccurate cut.
How can the following sawing factors be increased? Tool life Accuracy
Tool life: Slower Tool Velocity (Fewer Teeth per min), Finer Pitch Band Tool (More Teeth and Smaller Gullets), Medium Feeding Rate, and Claw Tooth (Positive Rake Angle.) Accuracy: Faster Tool Velocity (More Teeth per min) and Slower Feeding Rate (Decrease Chip Load)
Briefly outline the procedure for tapping a blind hole.
Use all three taps in order: taper, plug, and then the bottoming tap. Before the bottoming tap, remove all the chips from the hole and do not hit the bottom of the hole with the tap.
Name five materials that can be cut satisfactorily with knife-edge bands.
Used for cutting soft, fibrous materials cloth, cardboard, cork, and rubber.
For what purpose are soft faced hammers used?
Used in assembling or dismantling parts so the finished surface of the work will not be marred. (heads made of plastic, rawhide, copper, or lead.)
What is the advantage of a drill jig?
Used in production for drilling holes in a large number of identical parts.
What is the purpose of a drill chuck?
Used on a drill press for holding straight-shank cutting tools.
Describe the following blade sets: Wave Straight Raker
Wave: Has a group of teeth offset to the right and the next group to the left, a pattern that produces a wavelike appearance. Wave-set blades are generally used when the cross section of the workpiece changes, such as on structural steel sections or on pipe. Straight: which has one tooth offset to the right and the next to the left. It is used for cutting light non ferrous castings, thin sheet metal, tubing, and Bakelite. Raker: which has one tooth offset to the right, one offset to the left, and the third tooth straight. This pattern is the most common and is used for most sawing applications.
What general rule applies when selecting the pitch of a saw blade?
When cutting thick materials, use a coarse-pitch blade; thin materials require a fine-pitch blade.
Micrometers- Each line on the sleeve? each numbered line on the sleeve? each line on the thimble?
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How can the machining quality for alloy steel be improved?
combinations of sulfur and lead or sulfur and manganese in proper proportions are sometimes added to alloy steels.
Why is cemented carbide used extensively in the manufacture of cutting tools?
extreme hardness and good wear-resistance properties of cemented carbide
Metric Micrometers- Read metric micrometer settings
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What conditions must be present to produce the Type 2 chip?
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Explain how a built-up edge is formed and state its effect on cutting-tool life.
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What is the advantage of tapping a hole by hand in a drill press?
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Why have coordinate measuring systems been so widely accepted by the industry?
widely used in the field of measurement and inspection, provide a quick and accurate means of checking machined parts prior to assembly.
Use the formula and calculate the tap drill size for: ½ in.-13 UNC tap M 42-4.5mm tap Formula: TDS = D - 1/n
½ - 1/13 = .5 - .076 = .042 42 - 4.5 = 37.5
