Final Machine Tool

COMPUTER INTEGRATED MANUFACTURING MACHINE TOOLS Submitted To: Sir Zahid Submitted By: Tayyaba Noreen Hurria Afzal Asfa

(BSIEM06-01) (BSIEM06-30) (BSIEM06-35)

Date of Submission: 14-09-2009

IQTM

Q.1: Ans: IMPORTANCE OF MACHINE TOOLS TO OUR SOCIETY: The machine tools are of great strategic importance to economic growth and to nation’s comparative international position both economically and militarily. Virtually every manufactured product is produced on machine tool s or on machines built by machine tools. Machine tools are crucial to a great variety of industrial processes and commercial products. General economic growth depends closely upon the availability of machine tools for the manufacture of new products. They have become important also because of their durability and precision. They are so good at boosting the productivity that nearly every manufacturer is forced to use them. They have contributed in the birth of product engineering and mass production. With the machine tools many new technologies have developed such as areas of electronics, optics and aero space etc.

Q.2: Ans: DIFFERENCE BETWEEN TOOL AND MACHINE TOOL: Common Tool: A tool is a device or a piece of equipment which typically provides a mechanical advantage in accomplishing a physical task, or provides an ability that is not naturally available to the user of a tool. These tools are hand-held, portable powers, or manual tools.

Machine Tool:

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It is machining equipment that cuts, shears, punches, presses, drills, rolls, grinds, sands, or forms metal, plastic, or wood stock. It may be automatic or semi-automatic. Machine tools are generally power- driven metal cutting or forming machines used to shape metals by: The removal of chips Pressing drawing or shearing Controlled electrical machining process Any machine tool has generally has capability of Holding and supporting the work piece Holding and supporting a cutting tool Imparting a suitable movement (rotating or reciprocating) to the cutting tool or the work Feeding the cutting tool so that the desired cutting action and accuracy will be achieved The performance of any machine too is generally stated in terms of its metal removal rate, accuracy and repeatability.

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Q.3: Ans: SIZE DESIGNATION OF VARIOUS MACHINE TOOLS: The Lathe: Lathe size is determined by the swing and length of bed. Swing indicates the largest diameter that can be turned over the ways (flat or v-shaped bearing surface that aligns and guides moveable parts of machines). Bed length is entire length of the ways. Bed length must not be mistaken for the maximum length of the work that can be turned between centers. The longest piece that can be turned is equal to the length of the bed minus the distance taken up by the headstock and tailstock.

Milling Machine: The size of a milling machine is based on the longitudinal (from left to right) table travel, in inches. Vertical, cross, and longitudinal travel are all closely related as far as the overall capacity. However, for size designation, only the longitudinal travel is used.

The Shaper: The size of a shaper is designated by the maximum length of stroke or cut it can take.

Drill Press: The size may be designated in different ways by different companies. Some companies state the size as distance from the centre of spindle to column of machine; others specify size by diameter of largest circular piece that can be drilled in the center.

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Q.5: Ans: VARIOUS OPERATIONS PERFORMED ON MACHINE TOOLS: The Lathe: • • • • • • • • •

Turning: Produces straight, conical, curved, or grooved work pieces Facing: Produces a flat surface at the end of the part Boring: To enlarge a hole Drilling: To produce a hole Cutting off: To cut off a work piece Threading: To produce threads Knurling: Produces a regularly shaped roughness Profiling: To turn cylindrical work pieces with rough and finished cuts Grooving: To make furrows or channels

Milling Machine: • •

Peripheral milling: It is done when the surface being machined is PARALLEL with the PERIPHERY of the cutter. Face milling: Face milling is the process of producing a flat vertical surface at right angle to the cutter axis

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Side milling: Side milling is used to machine a vertical surface on the sides or the ends of a work piece Plane Milling or Surface Milling: This is the machining of plain, flat, horizontal surfaces by means of cylindrical mills whose length is usually much greater than their diameters, the larger kinds being constructed with inserted blades or teeth. Angle Milling: As the name suggests, this is the machining of a surface at some other than a right angle to the axis of the milling cutter. Form Milling: The machining of some special cross-section generally composed of straight lines and curves, or wholly of curves, is called form milling. Profiling: This operation is usually considered as machining the vertical edges of pieces of irregular contour, and is generally done with an end mill mounted in a vertical spindle. The exact form is generally determined by a templet or profile attached to the piece or to the fixture supporting it. Slab milling: Machining flat surfaces which are parallel to the axis of the cutter. Special Operations: o Routing is a term applied to milling an irregular outline while controlling the work piece movement by hand feed. o Grooving reamers and taps is called fluting. o Gang milling is the term applied to an operation in which two or more milling cutters are used together on one arbor. o Straddle milling is the term given to an operation in which two milling cutters are used to straddle the work piece and mill both sides at the same time

The Shaper: The shaper operations are almost the same as those performed on milling machine the reason why the shaper is used is that milling cutters of the correct size and angle are not always readily available and to obtain them especially for occasional use would not be in the interest of economy. For the shaper, however, a tool for any special shape can be prepared in a short time, often by grinding the form on to a standard tool which is already near to the form required.

Drilling Machine: • •

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Drilling: Producing cylindrical hole with tool called drill. It is simplest method of making hole. Drilled hole always has rough surface and is oversized. Reaming: It is an accurate way of sizing and finishing a hole which has been drilled previously. Hole has to be drilled undersized to be reamed. Reamer cannot originate hole and is rotated at half the speed of drilling. Reamer cannot correct hole location. The material removed is in the range 0.125 to 0.375mm. Boring: Enlarge the hole with adjustable tool. It is suitable for making odd size hole and is used as finishing operation. It is used to machine surfaces of casted holes. It can be used to correct out-off roundness of hole and to correct location of hole. Its accuracy is as high as ±0.00125mm and requires several passes of tool.

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Counter-boring: Enlarging end of the hole. The enlarged hole forms square shoulder. It is used to accommodate bolts, nuts, etc. counter-boring tool has straight or taper shank. Pilot guides the tool. Accuracy of operation is ±0.05mm. Counter-sinking: Making cone-shaped end enlargement. There is a seat for screw or rivet head (conical shaped). Spot facing: Smoothing and squaring surface around hole for nut or screw head Tapping: Operation of cutting internal thread by a tool called tap. Tapping can be performed manually or by machine. Tap is a bolt with threads on it. Threads of tap act as cutting edges and remove metal and cuts internal threads. Tapping is done on hole having smaller diameters than outside diameter of thread. Trepanning: It is the operation of producing hole by removing metal along the circumference of a hollow cutting tool and is used for producing large holes. Tool is in the form of a hollow tube with cutting edges at one end and solid shank at other end to fit in drill spindle. There is saving of material while drilling the hole. Lapping: Using lap, holes can be accurately finished/polished. Grinding: With grinding wheel mounted on spindle, made to feed up and down

Q.6: Ans: CUTTING FEED AND SPEED OF VARIOUS MACHINE TOOLS: Cutting Speed: The speed in surface feet per minute or meters per minute at which the metal may be machined efficiently

Lathe Cutting Speed: It may be defined as the rate at which a point on the work circumferences travels past the cutting tool. When work is machined in a lathe, it must be turned at a specific number of revolutions per minute(r/mint), depending on its diameter, to achieve the proper cutting speed. Cutting speed is always expressed in feet per minute (ft/mint) or in meters per minute (m/mint).

Drill Press Cutting Speed: The speed of a drill is generally referred to as a cutting speed, surface speed or peripheral speed. It is the distance that a point on the circumference of a drill will travel in 1 minute.

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Milling Machine Cutting Speed: When work is machined in a milling machine, the cutter must be revolved at a specific number of revolutions per minute(r/mint), depending on its diameter, to achieve the proper cutting speed.

Formula: Cutting speed of lathe drill press and milling machine can be find out from this formula In Inches: r/mint=CS*12/πD In Metric: r/mint=CS*320/D

Milling Machine Feed: The milling feed is determined by multiplying the chip size (chip per tooth) desired, the number of teeth in the cutter, and the r/mint of the cutter. Drill Press Feed: Feed is the distance that a drill advances into the work for each revolution. Drill feed may be expressed in decimals, fractions of an inch, or millimeters.

Lathe Feed: The feed of a lathe may be defined as the distance the cutting tool advances along the length of work for every revolution of spindle. Feed of the lathe is dependent on the speed of the lead screw or feed rod. Speed is controlled by the change gears in the quick – change gear box.

Q.7: Ans: COMMON PARTS AND FEATURES OF BASIC MACHINE TOOLS: Common Parts: • • • • • • • • • •

Electric motor Transmission mechanism Spindle Base or bed Slides or ways Cutting tool Mechanisms for different movements Different levers, hand wheels and gauges Work piece holding device Accessories

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Common Features: (Specify material removal rate) • •

Cutting speed Feed rate

Q.8: Ans: BASE OF CAST IRON OF MACHINE TOOLS: Cast iron is still one of the basic structural materials in machine tools, for two main reasons: its operational and technological properties are excellent; and its potential is far from exhausted.

ADVANTAGES OF CAST IRON: • • • • •

Good strength to weight ratio Typically lower cost than competing materials and relatively low cost per unit of strength than other materials. Lower density and higher thermal conductivity than steels at comparable tensile strength levels. Excellent machinability, allowing for high speeds and feeds and reduced (minimal) energy due to the presence o f free graphite. Greater Tensile strength, Compressive Strength, Shear Modulus of Rupture and Endurance Limit.

Q.9: Ans: USE OF HOLES IN BASE OF MACHINE TOOLS: After casting and cleaning operations, the bottom surface are machined in a shaping machine and two holes drilled to set screws to clamp the guide strip. The jaw bearings are taken up next. Holes are first drilled of diameter suitable for the screws which are used to facilitate the jaw adjustment. Later these holes are enlarged on the inner end to suit the size of jaws. Subsequently the smaller diameter ends of the holes are suitably tapped. After the spot facing the required location, holes are drilled and tapped for set screws which will clamp the jaw in position.

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Q.10: Ans: USE OF SLOTS WITH TABLES: Slots are used to permit clamping of the work. They are used for locating the work piece itself or for mounting various holding devices and attachments. They prevent work piece from vibrations during machining. They can also provide the means for lining up a surface parallel or perpendicular to important axes (e.g. spindle) on the machine.

Q.11: Ans: LIST OF DIFFERENT TAPER SHANK TOOLS: • • • • • • • • • • • • • • • • • • • • •

Lathe centers Collect chucks End mills T-slot cutter Dove tail cutter Key less drill chucks Light boring tool with bent shank Arbor for shell reamer Flute chucking reamer Taper pin reamer Arbor (mandrel) Spiral end mill Woodruff key-seat cutter Spiral double-end mill Extra long spiral-end mill Drill for molded plastics Four-fluted drill Three-fluted drill High helix drill Fluted tipped shell expansion reamer Taper shank oil drill hole

ADVANTAGE OF USING TAPER SHANK TOOLS: It makes contact with the grub screw (a place to hold the other tool within it) and makes contact to increase the torque of the tool without the tool slipping. The diameter of the shank can differ with the reference to the tool. The taper is used to make the tool hold 9

firmly and for faster operations. The taper shank doesn’t need any threading on it as its shape is the main advantage which reduces into angle and diameter.

Q.12: Ans: SLIDES OR WAYS USED IN MACHINE TOOLS: • •

Slide ways can be broadly classified in two categories: Closed Slide ways Open slide ways

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The most commonly used shapes of guide ways or slide ways are: Vee-Ways Flat-Ways Dovetail-Ways Hardened way slide Linear guide slide Cylindrical-Ways Roller ways Box ways

Q.13: Ans: FEATURES OF POWER TRANSMISSION MECHANISMS: Gear Mechanism: • •

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A gear, or toothed wheel, when in operation, may actually be considered as a lever with the additional feature that it can be rotated continuously, instead of rocking back and forth through a short distance. The gear that is closer to the source of power is called the driver, and the gear that receives power from the driver is called the driven gear. The driver gear meshes with driven gear and it begins to turn as well.

If a large gear turns a small gear the speed increases. On the other hand, if a small gear turns a large gear the opposite happens and the speed decreases.

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Rotational speed is proportional to a wheel's circumferential speed divided by its radius. The larger the radius of a gear, the slower will be its rotational speed, when meshed with a gear of given size and speed. The same conclusion can also be reached by a different analytical process: counting teeth. Since the teeth of two meshing gears are locked in a one to one correspondence, when all of the teeth of the smaller gear have passed the point where the gears meet -- i.e., when the smaller gear has made one revolution -- not all of the teeth of the larger gear will have passed that point -- the larger gear will have made less than one revolution. The smaller gear makes more revolutions in a given period of time; it turns faster. The speed ratio is simply the reciprocal ratio of the numbers of teeth on the two gears. (Speed A * Number of teeth A) = (Speed B * Number of teeth B) This ratio is known as the gear ratio. The pitch circle of a gear is very important as it is used by engineers to determine the shape of the teeth and the ratio between gears. The pitch of a gear is the distance between any point on one tooth and the same point on the next tooth. The pitch point is the point where gear teeth actually make contact with each other as they rotate. A gear train may have several drivers and several driven gears.

When gear A turns once clockwise, gear B turns 4 times counter-clockwise and gear C turns once clockwise. Hence gear B does not change the speed of C from what it would have been if geared directly to gear A, but it changes its direction from counterclockwise to clockwise. The velocity ratio of the first and last gears in a train of simple gears dose not change by putting any number of gears between them. Backlash is the error in motion that occurs when gears change direction. It exists because there is always some gap between the trailing face of the driving tooth and the leading face of the tooth behind it on the driven gear, and that gap must be closed before force can be transferred in the new direction. A pair of gears could be designed to have zero backlash, but this would presuppose perfection in manufacturing, uniform thermal expansion characteristics throughout the system, and no lubricant. Therefore, gear pairs are designed to have some backlash. Gear mechanism has highest torque/force capability; steel gears with large teeth can transfer tremendous torque. This mechanism requires high precision placement and alignment of gears. Gears could be noisy at high speeds; small teeth may slip under load due to bearing slop/play.

Belt and Pulley Mechanism: • •

Pulleys are nothing but gears without teeth and instead of running together directly they are made to drive one another by cords, ropes, cables, or belting of some kinds. By crossing the belt the direction of drive can be changed. Drive can be transferred by friction of the belt on the pulley or, if required, buy using a toothed belt. Pulley wheels are grooved so that the belt cannot slip off. Also, the belt is pulled

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tight between the two pulley wheels (in tension). The friction caused by this means that when the driver rotates the driven follows. If both pulleys have same diameter they will rotate at same speed. The velocities of pulleys are inversely proportional to their diameters in case of different size pulleys. For every single revolution of the larger driven pulley wheel, the smaller driver pulley wheel rotates twice. This is due to velocity ratio which can be calculated as: Velocity ratio = (Distance moved by driver pulley) / (Distance moved by driven pulley) The diagram shows a small driver pulley pulling round a larger driven pulley. The rpm (revolutions per minute) of the larger driven pulley wheel will be less than the smaller driver pulley wheel.

Pulley mechanism has lower torque capability; may slip under load. The belt will slip on a very small pulley because it cannot wrap tightly around a small radius. The fabrication ease level is of Medium difficulty. Pulleys must be held in tension. A flange on at least one side is required to prevent belt from slipping off pulley. The belt may stretch over time.

Q.14: Ans: LIST OF WORK PIECES AND CUTTING TOOL HOLDING DEVICES: Work and Cutting Tool Holding Devices for Lathes: • • • • • • • • •

A lathe dog Three Jaw chuck Four Jaw chuck Magnetic chuck Face plates Tool post Mandrels: There are 2 types: plain and expanding mandrels. Colet chuck Lathe center

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Steady rest Follower Rest Vice V-Block Angle plates Parallels

Work and Cutting Tool Holding Devices for Shaper: • • • •

Vise Adjustable screw stop Compressive clamp Inclined screw for T-slot

Work and Cutting Tool Holding Devices for Drilling Machines: • • • • • • • • • • • •

Spindle hole Drill chuck: i) Key-type drill chucks ii) Keyless drill chucks Drill socket Drill sleeve Step Blocks Clamps V-Blocks Angles Jigs T- Slots Bolt Machine Table Vice Fixtures

Work and Cutting Tool Holding Devices for The milling Machine: • • • • • • • • • • •

Vice: i) Swivel base vise ii) Plain Vise Parallels End mill adaptors Fixtures Motorized over arm attachment Slotting attachment Circular table Rack milling attachment Arbors Collets Indexing or dividing head

iii) Universal vise

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Q.15: Ans: MECHANISMS USED FOR MOVEMENT OF DIFFERENT PARTS OF MACHINE TOOLS: Rack and Pinion Gear Mechanism: The rack and pinion gear mechanism is used to convert between linear and rotary motion. Often the pinion rotates in a fixed position and the rack is free to move. Alternatively, the rack may be fixed and the pinion rotates moving up and down the rack. This latter arrangement is used as the drive mechanism for portable lathe or end shaft turning machine adapted for mounting on a work piece to be machined and includes a cutting tool which is mounted on an axially driven turning bar. The turning bar is advanced by a rack-and-pinion mechanism, the pinion being advanced by pivotal movement of a clutch mechanism. The clutch mechanism is pivoted by the upward and downward movement of push rods that engage a cam mechanism as the lathe body is rotated about a central spindle. The portable drill press has a rack bar with a brace attached at one end. A pinion slide assembly is slid ably engaged with the rack bar such that the pinion is in rotational engagement with a rack. The pinion slide assembly may be retained on the rack bar by a bolt. The pinion may be attached to a pinion shaft that may be rotated by a rotation lever. A mounting bracket may be attached to the pinion slide assembly for attachment of a hand drill.

Quick Return Mechanism: Quick return mechanism is used where there is a need to convert rotary motion into reciprocating motion. As the disc rotates the black slide moves forwards and backwards. The quick return mechanism is used in shaping machine is used to machine flat metal surfaces especially where a large amount of metal has to be removed. As the disc rotates the top of the machine moves forwards and backwards, pushing a cutting tool. The cutting tool removes the metal from work which is carefully bolted down. The quick return mechanism in milling is used to move crank shaft drive ram, connecting rod and slider block that holds the work piece. The quick and return mechanism in drill press is also used to move the drill head or cam. Drill head and cam are moved by two electrical motors. Cam move opposite direction of drill head when cam returned to is original position then clutch is disengaged.

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Belt and Pulley Mechanism: Belt and Pulley Mechanism transfer rotating motion from one shaft to another. A belt tensioning device is provided for an apparatus such as a lathe which includes a centering member adapted to be attached to a work piece and is supported for rotation about an axis. A motor is spaced from the centering member and is supported by a pivot member. A drive pulley is attached to the motor and a driven pulley is attached to the centering member. A belt is engaged between the drive pulley and the driven pulley for transmitting driving torque from the motor to the centering member. A belt tensioning device is provided for moving the pivot member between a first position wherein the belt is tensioned between the drive and driven pulleys and a second position wherein the belt is loosened between the drive and driven pulleys In milling machine if both pulleys have the same speed then they will move in same speed. If one pulley is larger then the other, than mechanical advantage and pulley ratio are gained. . A speed adjusting device for a drill press includes a first variable pulley mounted to the motor shaft and a second variable pulley mounted to the output shaft with a belt connected between the two variable pulleys. A pressing member is mounted to the second variable pulley and the first end of the pressing member is pivotally connected to a fixed member and the second end of the pressing member is connected to a control device. The control device has a connecting member connected to the second end of the pressing member so that the pressing member exerts a force to the second variable pulley by operating the control device to adjust the effective diameter of the belt in the first and the second variable pulley.

Quick Tool Release Mechanism: Tool/collets alignment and secure arrangement for a vertical milling machine having a Jhead and a manually adjustable spindle for the secure and rapid change of a tool held in a collet in a lower end of the spindle. Arrangements of receiving bores are spaced annularly around the lower end of the spindle. An arrangement of locating pins are correspondingly arranged about the tool/collet so as to mate with the receiving bores in the spindle, to provide secure and efficient engagement of the collet/tool with the spindle in the vertical milling machine.

Carriage Feed mechanism: This operation is also performed in lathe. Carriage holds the tool bit and moves it longitudinally (turning) or perpendicularly (facing) under the control of the operator. The operator moves the carriage manually via the hand wheel or automatically by engaging the feed screw with the carriage feed mechanism.

Multiple Gear Mechanism: Multiple gears can be connected together to form a gear train. If there are an odd number of gears, the output rotation will be the same direction as the input. If there are even 15

numbers, the output will rotate in the opposite direction to the input. Note that for the simple type of gear train shown, the number of teeth on the intermediate gears does not affect the overall velocity ratio which is governed purely by the number of teeth on the first and last cog. The lathe must be stopped before speed change by means of manually operating a gear lever. It is a primary object of the present invention to provide an improved speed change gear mechanism that includes various sets of gears to provide various speeds and to allow speed change without stopping the lathe. It can also be used in milling machines.

Drive Mechanism: It is the object of this invention to provide a drive mechanism for producing angular movement of a work spindle on a lathe in a convenient and efficient form. A drive mechanism for producing angular movement of a work spindle on a multi spindle lathe comprises an electrical stepping motor connected to the spindle through dis-connectible drive means, the spindle also having an associated brake.

Q.16: Ans: CUTTING TOOL MATERIALS AND PROPERTIES IMPARTED BY THESE MATERIALS ON CUTTING TOOL: High Carbon Steel: This material is one of the earliest cutting materials used in machining. It is however now virtually superseded by other materials used in engineering because it starts to temper at about 220oC. This softening process continues as the temperature rises. As a result cutting using this material for tools is limited to speeds up to 0.15 m/s for machining mild steel with lots of coolant.

High Speed Steel (HSS): This range of metal contains about 7% carbon, 4% chromium plus additions of tungsten, vanadium, molybdenum and cobalt. These metals maintain their hardness at temperature up to about 600, but soften rapidly at higher temperatures. These materials are suitable for cutting mild steel at speeds up maximum rates of 0.8 m/s to 1.8 m/s.

Cast Alloys: These cutting tools are made of various nonferrous metals in a cobalt base. They can withstand cutting temperatures of up to 760oC and are capable of cutting speeds about 60% higher than HSS.

Stellite:

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This is a cast alloy of Co (40 to 50%), Cr (27 to 32%), W (14 to 19%) and C (2%). Stellite is quite tough and more heat and wear resistive than the basic HSS (18 – 4 – 1) But such stellite as cutting tool material became obsolete for its poor grindability and especially after the arrival of cemented carbides.

Cemented carbides (cermet) (sintered carbide): This material usually consists of tungsten carbide or a mixture of tungsten carbide, titanium, or tantalum carbide in powder form, sintered in a matrix of cobalt or nickel. As this material is expensive and has low rupture strength it is normally made in the form of tips which are brazed or clamped on a steel shank. The clamped tips are generally used as throw away inserts.

Coated Carbides: The cutting system is based on providing a thin layer of high wear-resistant titanium carbide fused to a conventional tough grade carbide insert, thus achieving a tool combining the wear resistance of one material with the wear resistance of another. These systems provide a longer wear resistance and a higher cutting speed compared to conventional carbides.

Ceramics: Ceramics are made by powder metallurgy from aluminium oxide with additions of titanium oxide and magnesium oxide to improve cutting properties. These have a very high hot resistance and wear resistance and can cut at very high speed. However they are brittle and have little resistance to shock. Their use is therefore limited to tips used for continuous high speed cutting on vibration-free machines.

Diamonds: Diamonds have limited application due to the high cost and the small size of the stones. They are used on very hard materials to produce a fine finish and on soft materials especially those inclined to clog other cutting materials. They are generally used at very high cutting speed with low feed and light cuts. Due to the brittleness of the diamonds the machine has to be designed to be vibration free. The tools last for 10 (up to 400) times longer than carbide based tools.

Q.17: Ans: DIFFERENCE BETWEEN CONVENTIONAL MACHINE TOOLS AND CNC MACHINE TOOLS: CNC or "computer numerical controlled" machines are sophisticated metalworking tools that can create complicated parts required by modern technology. Growing rapidly 17

with the advances in computers, CNCs can be found performing work as lathes, milling machines, laser cutters, abrasive jet cutters, punch presses, press brakes, and other industrial tools CNC is 'computer numeric controls' meaning the dimensions are programmed into a computer and it directs the equipment to perform specific functions. With the advent of cheap computers, free operating systems such as Linux, and open source CNC software, the entry price of CNC machines has plummeted. The CNC machines are often totally enclosed, due in large part to Occupational health and safety (OH&S) issues. The machine is controlled electronically via a computer menu style interface; the program may be modified and displayed at the machine, along with a simulated view of the process. The setter/operator needs a high level of skill to perform the process, however the knowledge base is broader compared to the older production machines where intimate knowledge of each machine was considered essential.

A drill press (also known as pedestal drill, pillar drill, or bench drill) is a fixed style of drill that may be mounted on a stand or bolted to the floor or workbench. A drill press consists of a base, column (or pillar), table, spindle (or quill), and drill head, usually driven by an induction motor.

Computer Numerical Control (CNC) Drilling is commonly implemented for mass production. The appropriate CNC drill press is brought into position through movement of the turret, so that bits do not need to be removed and replaced. CNC drill presses are controlled by computers and different software programs are used to control these movements of machine. CNC drill press which, on command, drills a hole of a set diameters and depth into a part set up beneath it. The largest time sink for CNC drilling is with tool changes, so for speed, variation of hole diameters should be minimized. Conventional Lathe: The machine has been greatly modified for various applications however a familiarity with the basics shows the similarities between types. This machine consist of, a headstock, bed, feed and lead screws, carriage, cross slide, compound rest, tool post and tailstock. The better machines are solidly constructed with broad bearing surfaces (slides or ways) for stability and

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manufactured with great precision. This helps ensure the components manufactured on the machines can meet the required tolerances and repeatability. CNC lathes are rapidly replacing the older production lathes (multi spindle, etc) due to their ease of setting and operation. They are designed to use modern carbide tooling and fully utilize modern processes. The part may be designed and the tool paths programmed by the CAD/CAM process, and the resulting file uploaded to the machine, and once set and trialed the machine will continue to turn out parts under the occasional supervision of an operator. A milling machine is a machine tool used for the shaping of metal and other solid materials. Milling machines exist in two basic forms: horizontal and vertical, which terms refer to the orientation of the cutting tool spindle. Milling machine consist of base, column, knee, table, overhanging arm, front brace and arbor. The parts of the manual mill are separated in diagram. The knee moves up and down the column on guide ways in the column. The table can move in x and y on the knee and the milling head can move up and down. Typically, conventional milling is used for roughing the part to size, requiring less force. CNC milling machines are traditionally programmed using a set of commands known as G-codes. G-codes represent specific CNC functions in alphanumeric format. Computer Numerical Control (CNC) Milling is the most common form of CNC. CNC mills can perform the functions of drilling and often turning. CNC Mills are classified according to the number of axes that they possess. Axes are labeled as x and y for horizontal movement, and z for vertical movement, as shown in this view of a manual mill table. Most CNC milling machines (also called machining centers) are computer controlled vertical mills with the ability to move the spindle vertically along the Z-axis. A standard manual light-duty mill (such as a Bridgeport) is typically assumed to have four axes: Table x Table y Table z Milling Head z The most advanced CNC milling-machines, the 5-axis machines, add two more axes in addition to the three normal axes (XYZ). Horizontal milling machines also have a C or Q axis, allowing the horizontally mounted work piece to be rotated, essentially allowing asymmetric and eccentric turning. The fifth axis (B axis) controls the tilt of the tool itself. When all of these axes are used in conjunction with each other, extremely complicated geometries, even organic geometries such as a human head can be made with relative ease with these machines. But the skill to program such geometries is beyond that of most operators. Therefore, 5-axis milling machines are practically always programmed with CAM.

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REFRENCES: http://ase.tufts.edu/mechanical/shop/classes/me1/lathe.htm http://opensourcemachine.org/wp-content/uploads/2008/10/us-army-machinist-coursemilling-machine-operations-od1644-ww.pdf http://science.jrank.org/pages/4041/Machine-Tools-Shapers.html http://www.roymech.co.uk/Useful_Tables/Manufacturing/CutMat.html http://www.cs.cmu.edu/~rapidproto/mechanisms/chpt2.html http://www.technologystudent.com/gears1/pulley4.htm http://maelabs.ucsd.edu/mae_guides/machine_design/power_transmission/pros_cons.htm http://books.google.com.pk Holding device for milling machines - Patent 4930954 Machine Shop 3 - Basic Milling Types - Work Holding workpiece and cutting tool holding devices of milling machine - Google Search Tech Of Machine Tools (Sie) - Google Books http://www.pdfcoke.com/doc/11621489/15-Cutting-Tool-Materials-of-Common-Use www.efunda.com What does shank mean? definition, meaning and pronunciation (Free English Language Dictionary) http://www.icscuttingtools.com/catalog/page_095.pdf Machine taper - Wikipedia, the free encyclopedia ICS Cutting Tools - taper shank accessories

Technology of machine tools by J.F.Karar

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