AENG 11 Engineering Shop Asst. Prof. Mark Keylord S. Onal
VI. METAL WORK MATERIALS
General Classification of Metals Used in Bench Metal Work: 1. Ferrous Metals (wrought iron, steel, and cast iron) 2. Non-ferrous Metals (copper, brass, bronze, and aluminum) *All these material come in various forms and shapes such as sheets, rods, bars, and wires. Common Metals and Their Major Use • Cast Iron - origin: iron ore - characteristics: forms into any shape; brittle - major use: machinery parts; engine blocks • Wrought Iron - origin: iron ore - characteristics: malleable; tough; rust-resistant - major use: decorative fences; railings • Mild Steel - origin: iron ore - characteristics: malleable; ductile; tough - major use: structural steel • Tool Steel - origin: iron ore - characteristics: high carbon; heat treatable; expensive - major use: tools; tool bits • Stainless Steel - origin: iron ore, nickel, and chromium - characteristics: corrosion resistant; bright appearance; tough - major use: food handling equipment; restaurant equipment • Galvanized Steel - origin: steel, zinc - characteristics: zinc-coated steel - major use: water tanks; towers; fencing; roofing
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AENG 11 Engineering Shop Asst. Prof. Mark Keylord S. Onal
• Aluminum - origin: ore - characteristics: light; relatively soft; good electrical conductor; tough; silver-white color - major use: truck bodies; automobiles; electrical wires/cables • Copper - origin: ore - characteristics: malleable; corrosion-resistant; heat/electrical conductor; tough; reddish-brown color - major use: machinery parts; engine blocks • Brass - origin: ore - characteristics: soft; malleable; corrosion resistant - major use: water valves; boat accessories; ornaments • Bronze - origin: copper, zinc, and tin - characteristics: soft; malleable; corrosion resistant - major use: ornaments • Lead - origin: ore - characteristics: soft; very heavy; bluish gray color - major use: batteries; cable coverings; solder • Tin - origin: ore - characteristics: very malleable; corrosion resistant; silver color - major use: plating; bronze; solder SHEET MATERIALS Metal sheets are widely used because these are easily shaped using cold working methods. Thickness of the metal sheet is designated by a series of numbers called gauges. The US Standard Gauge is commonly used for iron and steel sheets, while the Brown and Sharpe (in terms of weight per unit area) is used for other metals.
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AENG 11 Engineering Shop Asst. Prof. Mark Keylord S. Onal
Black Iron Sheets (BI) - black annealed sheets with standard sizes of gauges - not protected from rusting - used primarily for work that would be finished with paint Galvanized Iron Sheets (GI) - steel sheets coated with a thin layer of zinc on the surface - used for garbage cans, funnels, gutters, roofing, air ducts, and other jobs Galvanealed Sheets - freshly galvanized sheets kept hot for a few minutes to allow the zinc to actually mix or alloy with the steel giving the sheet a smooth, even and non-shiny appearance - does not crack nor peel regardless of how severe the conditions the sheet will be exposed Aluminum Sheets - can be purchased in various degrees of hardness such as 2S, 3S, etc.. where 3S is harder than 2S - will meet the requirements of most shop projects such as trays, bowls, and lamps Copper Sheets - widely used because of their attractive appearance - thickness may be given in gauges or in weight (oz/ft2) Brass Sheets - the gauge is measured by B&S system
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AENG 11 Engineering Shop Asst. Prof. Mark Keylord S. Onal
BAR MATERIALS Hot-rolled Iron Bars - often called mild steel bars in rectangular, angular, and square shapes - the bars can be pounded, twisted and bent into many shapes - often used as replacement for wrought iron because it is less expensive Rectangular Bars - size varies in thickness from 1/16” to 3/8” and in width from ½” to 2” with a length of 20 ft Angular Bars - useful as bench legs, for reinforcing corners and for making projects of all kinds - the common sizes are 1/16 x ½ x ½, 1/16 x ¾ x ¾, 1/8 x 1 x 1, etc.. with a length of 20 ft Round Bars - are mild steel bars sold in diameters from 3/16” to 2” and length of 12 ft to 20 ft Square Bars - from 1/4” up to 2” in size WIRE MATERIALS - are produced by drawing cold rods through successive sets of dies - the diameter of the wire is indicated by AWG (American Wire Gauge) number - wires may be purchased as galvanized, tinned, bright, coppered or annealed, to suit the needs of the shop
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AENG 11 Engineering Shop Asst. Prof. Mark Keylord S. Onal
VII. FASTENING MATERIALS AND OTHER HARDWARES
Hardware - are usually metals used in project for assembling, beautifying, and as mechanical devices to facilitate movement Fasteners - are materials for securely joining separate parts of an object or structure Trivia: Jumbo jets such as Boeing’s 747 and Lockheed’s L1011 require as many as 1.5 million fasteners. The 747 for example need about 70,000 titanium fasteners, 400,000 close tolerance fasteners, 30,000 squeeze rivets. TYPES OF FASTENERS a. Temporary b. Semi-permanent c. Permanent Temporary - includes screws, nuts and bolts - these are externally threaded to allow fastening in which the part to be assembled together can easily be dismantled without any damage - a bolt is generally inserted through a hole and fastened by fitting a nut over the end of the bolt - the nut has internal threads that mate with the external threads of the bolt - the combination of a bolt and a nut may be used to join and hold structures together - a screw, on the other hand, requires no nut because it is anchored directly in the work piece
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AENG 11 Engineering Shop Asst. Prof. Mark Keylord S. Onal
Semi Permanent - it includes the nails - these are fasteners that are driven into the material it holds - there are many types of nails classified generally by their use or form - when buying nails, the purchaser should know the use for the nail, the desired length, and the desired thickness or diameter
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AENG 11 Engineering Shop Asst. Prof. Mark Keylord S. Onal
Permanent - it includes the rivets - fastening materials generally used to join metallic materials such as sheets and bars by spreading one or both ends
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AENG 11 Engineering Shop Asst. Prof. Mark Keylord S. Onal
OTHER HARDWARES - these include hinges, brackets, plates, and miscellaneous metal objects.
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AENG 11 Engineering Shop Asst. Prof. Mark Keylord S. Onal
THE LATHE MACHINE
- the lathe is a metal turning machine tool in which metal is removed on a piece of work by slowly moving (feeding) a suitably formed cutting tool against a revolving piece of work - the direction of the feed may be more or less parallel to the axis of the work (longitudinal feed) or in a direction at right angles to the axis of the work (cross feed)
PRINCIPAL PARTS OF THE LATHE 1. BED – Often called the backbone of the lathe. The accuracy of the lathe depends upon the rigidity alignment and accuracy of the bed. The top surfaces, called ways, are machined to form inverted V’s and flat sides. 2. HEADSTOCK- It is located on the operator’s left. It supports and houses the spindle and the means of turning the spindle.
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AENG 11 Engineering Shop Asst. Prof. Mark Keylord S. Onal
3. TAILSTOCK- The moveable casting headstock on the ways of the bed.
located
opposite
the
4. CARRIAGE- The movable part which slides over the ways between the headstock and the tailstock. It carries the cutting tool and precisely controls its movements. 5. POWER FEED AND THREAD CUTTING MECHANISM- Transmits power from the spindle for precise longitudinal motion of the carriage as a whole. COMMON TYPES OF LATHE 1. BENCH LATHE- a small lathe usually mounted on a workbench and used for small work. 2. ENGINE LATHE- larger than the bench lathe, it is the most common kinds of lathe in the shop and is the most valuable machine tool in the shop. 3. TURRET LATHE- A major departure from the engine or basic lathes. These machines possess special features that adapt them to production. The skill of the worker has been built into these machines, making it possible for inexperienced operators to produce identical parts. 4. CNC Lathe - Same idea as a turret lathe but on computer control
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AENG 11 Engineering Shop Asst. Prof. Mark Keylord S. Onal
DIFFERENT LATHE OPERATIONS
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AENG 11 Engineering Shop Asst. Prof. Mark Keylord S. Onal
DRILLING MACHINE
.
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AENG 11 Engineering Shop Asst. Prof. Mark Keylord S. Onal
CUTTING TOOLS FOR DRILLING OPERATIONS 1. Twist drill - most common type of drill. It has two cutting edges and two helical flutes that continue over the length of the drill body.
2. Core drill - may have either three or four flutes. It is employed for enlarging previously made holes and not for originating holes. Characterized by greater productivity, high machining accuracy, and superior quality of the drilled holes.
3. Gun drill - used for drilling deep holes. All gun drills are straightfluted, and each has a single cutting edge.
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AENG 11 Engineering Shop Asst. Prof. Mark Keylord S. Onal
4. Spade drill - used for drilling large holes of 3.5" (90 mm) or more.
5. Saw-type cutters - used for cutting large holes in thin metal.
TYPES OF DRILLING OPERATIONS 1. Boring - involves enlarging a hole that has already been drilled. Similar to internal turning and can be performed on a lathe. 2. Counterboring - as a result, only one end of the drilled hole is enlarged. 3. Spot facing - performed to finish off a small surface area around the opening of a hole. 4. Countersinking - done to enable accommodating the conical seat of a flathead screw so that the screw does not appear above the surface of the part.
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AENG 11 Engineering Shop Asst. Prof. Mark Keylord S. Onal
5. Reaming - actually a "sizing" process, by which an already drilled hole is slightly enlarged to the desired size. Very smooth surface is obtained as a result.
6. Tapping - is the process of cutting internal threads. The tool used is called a tap.
CLASSIFICATION OF DRILLING MACHINES (DM) 1. Bench-type dm - general-purpose, small machine tools that are usually placed on benches. This type of drilling machine includes an electric motor as the source of motion, which transmitted via pulley and belts to the spindle, where the tool is mounted.
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AENG 11 Engineering Shop Asst. Prof. Mark Keylord S. Onal
2. Upright dm - can be used for light, medium, and even relatively heavy jobs. It is basically similar to bench-type machines, the main difference being a longer cylinder column fixed to the base. Along that column is a sliding table that can be adjusted to a desired height.
3. Multispindle dm - has sturdy construction and requires high power; each is capable of drilling many holes simultaneously. The positions of the spindles can be adjusted as desired. The whole head carrying the spindles and tools can also be tilted.
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AENG 11 Engineering Shop Asst. Prof. Mark Keylord S. Onal
4. Gang dm - when several separate heads are arranged in a single common table, the machine tool is referred to as a gang-drilling machine. It is particularly suitable where several operations are to be performed in succession.
5. Radial drill - particularly suitable for drilling holes in large and heavy work pieces that are inconvenient to mount on the table of upright drilling machine. The cantilever guide arm, which carries the drill head, can be moved along the column (up and down) and swung (left or right) at any desired position. The drill head can also slide along the arm.
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AENG 11 Engineering Shop Asst. Prof. Mark Keylord S. Onal
6. Turret dm - a common design feature is that the main spindle is replaced by a turret, which carries several drilling, boring, reaming, and threading tools. Several successive operations can be carried out with only a single initial setup.
7. Deep-hole dm - special machines employed for drilling long holes like those of rifle barrels. In this type of machine tool, it is the work piece that is rotated, while the drill is kept from rotary motion.
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AENG 11 Engineering Shop Asst. Prof. Mark Keylord S. Onal
8. Jig-boring machines - specially designed to possess high precision and accuracy. It can also locate holes because electronic measuring devices monitor the table movements.
DRILL PRESS SAFETY NOTES Requirements: Proper eye protection must be worn - operate only with instructor’s permission and after proper instructions have been received. 1. Always use a piece of scrap wood and set the table or stop to keep from drilling into the tabletop. 2. Use a clamp or vise grips to secure/fasten your wood to the table. 3. Make sure that your scrap wood, good wood, and any clamp you are using are the ONLY objects on the table. Other objects can get caught in the machine and cause injuries. 4. Use a “V-block” clamp for round, or irregular shaped stock. 5. Select the right size and type of bit. Wood bits for wood, metal bits for metal.
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AENG 11 Engineering Shop Asst. Prof. Mark Keylord S. Onal
6. Use a center punch for a guide whenever possible. Always use a center punch when drilling into metal or hard woods. 7. Do not panic if the bit gets stuck in the wood. Turn the machine off. When it has completely stopped, remove the bit from your wood. 8. Select the correct drilling speed. For metal or hard woods and large drill bits you should use a slower speed. 9. Always remove the chips from the table after the machine is turned off and is no longer moving. Use a table brush, never your hands. 10. As with any machine, if it is not working properly you should always turn it off, unplug it, and tell a teacher.
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AENG 11 Engineering Shop Asst. Prof. Mark Keylord S. Onal
SHIELDED-METAL ARC WELDING (SMAW)
- is one of the oldest, simplest, and most versatile arc welding processes. - the arc is generated by touching the tip of a coated electrode to the workpiece and withdrawing it quickly to an appropriate distance to maintain the arc - the heat generated melts a portion of the electrode tip, its coating, and the base metal in the immediate area - the weld forms out of the alloy of these materials as they solidify in the weld area - slag formed to protect the weld against forming oxides, nitrides, and inclusions must be removed after each pass to ensure a good weld - the SMAW process has the advantage of being relatively simple, only requiring a power supply, power cables, and electrode holder - the arc temperature can go up to 11,000 °F or 6,000 ° C
HOW THE ELECTRIC ARC IS EMPLOYED IN WELDING 1. A complete circuit is set up consisting of: a. Source of current b. Connecting cables c. Electrode holder with electrode d. Ground clamp e. Work piece
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AENG 11 Engineering Shop Asst. Prof. Mark Keylord S. Onal
2. The circuit is momentarily closed by touching the tip of the welding electrode to the work piece and withdrawing to a prescribed distance resulting in the formation of an arc. 3. The heat of the arc melts a localized area of the base metal and the tip of the electrode, forming small globules which are transferred to the base metal by hydrodynamic and electromagnetic forces (not by gravity) with the resulting fusion of the metals and solidification when the arc moves on. FUNCTIONS OF THE FLUX OR COATING 1. To protect the molten metal from the harmful effects of the oxygen and nitrogen in the air 2. To stabilize the arc 3. To improve the quality of the weld metal 4. To impart certain desired properties to the weld metal 5. To increase rate of deposition and welding speed CURRENT REQUIREMENTS 1. Amperage to be used depends on: a. kind of electrode b. size of electrode c. thickness of the plates to be welded d. welding position 2. Correct current is determined by actual tests and can be gauged by experience from: a. sound of arc b. size of molten pool c. appearance of bead d. penetration e. amount of spatter
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AENG 11 Engineering Shop Asst. Prof. Mark Keylord S. Onal
Note: When electrode becomes red-hot before it is all consumed, current used is higher than maximum recommended. This should not be allowed to happen, as penetration will actually be lower at the end of the run and visible pores (slag inclusions) will appear on the crater. EXPLANATION OF NAMING OF STEEL ELECTRODES 1. Code consists of letter E – plus 4 digits: E xxxx 2. E stands for electric arc welding electrodes. 3. First 2 digits indicate minimum tensile strength of the weld in thousand of psi. Examples: E 60xx – minimum tensile strength of deposit = 60,000 psi E 70xx – minimum tensile strength of deposit = 70,000 psi 4. Third digit refers to welding position as follows: E xx1x – all positions E xx2x – flat and horizontal E xx3x – flat position only 5. Fourth digit refers to the type of current to be used and indirectly to the kind of coating, as follows: E xx10 – DC reverse (cellulosic, Na) E xx11 – DC reverse or AC (cellulosic, K) E xxx2 – DC straight or AC (rutile, semi-cellulosic, Na, K) E xxx3 – DC straight or AC (high rutile, K) E xxx4 – DC either polarity or AC (rutile, iron powder, K) E xxx5 – DC reverse (low hydrogen or basic, Na) E xxx6 – DC reverse (low hydrogen or basic, K) E xx27 – DC either polarity or AC for flat position E xxx8 – DC reverse or AC (low hydrogen, iron powder, K) E xx20 – DC straight or AC (iron oxide, Na) E xx30 – DC either polarity or AC (high iron oxide, Na)
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AENG 11 Engineering Shop Asst. Prof. Mark Keylord S. Onal
Examples: 1. E 7010 is a cellulosic coated electrode with a guaranteed minimum tensile strength of 70,000 psi, suitable for welding in all positions, to be used with DC reverse current only. 2. E 6024 is a type of electrode containing iron powder in the coating with a minimum tensile strength of 60,000 psi, recommended for flat and horizontal welding only, and can be used with AC or DC of either polarity. SAFETY PRECAUTIONS 1. A welding helmet with a clean observation window must be worn. 2. Keep sleeves and pants cuff rolled down. 3. Goggles must be worn for all chipping operations. 4. Keep all flammable material away from working areas. 5. Always wear leather gloves, apron, and shoes when welding. 6. The floor area should be kept clear of all obstructions and dry. 7. Closed containers should not be welded without the instructor’s permission. 8. Report any overheating of the welding unit to the instructor at once. 9. Screens to protect others must be in place before welding is started. 10. The exhaust system must be turned on prior to welding.
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AENG 11 Engineering Shop Asst. Prof. Mark Keylord S. Onal
OXY-ACETYLENE WELDING
- commonly referred as gas welding - is a process which relies on combustion of oxygen and acetylene - when mixed together in correct proportions within a hand held torch or blowpipe, a relatively hot flame id produced with a temperature of about 3200 C - the chemical action of the oxyacetylene flame can be adjusted by changing the ratio of the volume of oxygen to acetylene
PREPARING THE METAL FOR WELDING 1. Before a successful weld can be made, the metal must be free of dirt, paint, oil, grease, rust, and other foreign matter. 2. Clean the metal by grinding, filing, scraping, sanding, and heating it with the welding torch and then brushing it with a wire brush. 3. Thick pieces of metal must be beveled on one or both sides to provide a larger welding surface and to allow the joint to be completely fused all the way through. 4. Bevel by grinding on a stationary or portable grinder, by chipping with a cold chisel or a regular chipping hammer, by sawing with a hand or power hacksaw, by filing, or by burning with a cutting torch. 5. Thin pieces of metal may be welded successfully without being beveled. TURNING OFF THE TORCH First, close the acetylene valve on the torch body, then close the oxygen tank valve. This assures the operator that the flame is out and will prevent any flashback that might leave a carbon deposit in the inside of the tip. If the acetylene is turned off last and the valve has a slight leak, a small flame may continue burning and fill
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AENG 11 Engineering Shop Asst. Prof. Mark Keylord S. Onal
the end of the tip with carbon. Close both the oxygen and acetylene valves off at the wall then bleed the hose lines by opening the torch valves until both gauges on each regulator register zero pressure. Finally, coil the hoses neatly and hang on the wall. TERMS AND DEFINITIONS • Fusion Welding – a method of joining two metals together by bringing the metals to a temperature that causes them to melt together • Direction of Travel – direction that the torch moves. • Oxy-Acetylene Cutting – a method of cutting metal using an oxyacetylene system • Acetylene – the fuel component used in an oxy-acetylene system • Envelope – the outermost portion of an oxy-acetylene flame (~2300° F) • Acetylene Feather – the middle portion of an oxy-acetylene flame produced by the presence of acetylene (~ 3800° F) • Inner cone – the innermost portion of an oxy-acetylene flame (~ 5700° F) • Carburizing Flame – a condition that exists when the acetylene feather is two times longer than the inner cone. This causes a greenish acetylene feather. • Neutral Flame – a condition that exists when the acetylene feather matches the length of the inner cone • Oxidizing Flame – a condition that exists when the inner cone is shorter than the acetylene feather. This causes a less luminous cone and a shorter deeper purple acetylene feather. • Travel Speed – the speed at which the welding, brazing or cutting takes place.
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AENG 11 Engineering Shop Asst. Prof. Mark Keylord S. Onal
SAFETY PRECAUTIONS Proper eye protection must be worn - operate only with instructor’s permission and after proper instructions have been received. Be sure cylinders are fastened with a chain as a protection against falling or rolling. 2. Always close the cylinder valve and replace protective cover before moving the cylinder. 3. Keep welding equipment free of oil and grease. 4. Protective goggles and spark-resistant clothing must be worn when welding. 5. Make sure that hoses are properly connected and all connections are tight. 6. Keep all flammable material away from working area. 7. Do not weld or cut on a closed container without instructor’s approval. 8. The acetylene must never exceed 15-psi outlet pressure. 9. Only use a friction torch lighter to ignite the torch. 10. Close the acetylene valve first if the torch backfires. 11. Close cylinder valves when completing a welding job. Release or drain hoses. 12. The exhaust system must be turned on prior to igniting the torch. 1.
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AENG 11 Engineering Shop Asst. Prof. Mark Keylord S. Onal
SHAPERS AND PLANERS
SHAPING AND PLANING - processes for machining horizontal, vertical, and inclined flat surfaces, slots, or grooves by means of a lathe-cutting tool - in all these processes, the cutting action takes place along a straight line Shaper • The cutting tool is reciprocated and the work piece is fed normal to the direction of the tool motion. • Can be employed in cutting external and internal keyways, gear racks, dovetails, and T-slots, and the like.
Planer • The work piece (and the machine bed) is reciprocated, and the tool is fed across the work piece to produce another straight line, thus generating a flat surface. • Designed to accommodate work pieces which are far greater in size than those in shaper.
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AENG 11 Engineering Shop Asst. Prof. Mark Keylord S. Onal
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AENG 11 Engineering Shop Asst. Prof. Mark Keylord S. Onal
THE MILLING MACHINE
- milling is the most versatile of the conventional machine tools - a cutter is held in a chuck which rotates at a controlled speed - the cutter is suspended over a work surface whose location can be precisely controlled - the part to be machined is securely fastened to the work surface, and the work surface is moved underneath the cutter - appropriate choices of cutter type, depth of cut and speed determine the final shape.
HORIZONTAL MILL
VERTICAL MILL
• There are three ways to cut using a mill. The edge of the piece can be cut (peripheral milling) or the surface of the piece can be cut (face milling).
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AENG 11 Engineering Shop Asst. Prof. Mark Keylord S. Onal
• The piece can be milled where the work is fed against the direction of the rotating milling cutter (up milling - a). This technique is best for surfaces with an initial rough finish. Alternatively, the work can be fed in the same direction as the cutter (down milling - b). This technique is best suited for intricate parts.
CUTTERS • Cutters are typically fabricated from high speed steel in a number of shapes and sizes. However, cutters can also be obtained in carbide or diamond for special milling operations.
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AENG 11 Engineering Shop Asst. Prof. Mark Keylord S. Onal
MATERIALS • materials best suited for milling are the softer metals and plastics • aluminum and brass are two commonly milled metals; teflon and delrin are commonly milled plastics • the ability to mill a metal is typically limited only by the hardness of the cutter • special cutters can be obtained for milling harder materials and refractories • very sharp cutters are available for plastics and even wood
SET-UP AND FIXTURING • a typical milling job requires more time to set up the fixturing to hold the job than to actually complete the job • fixturing is a critical part of the milling process • fixturing may involve fabrication of a number of other pieces before the actual part is manufactured
Common Milling Operations
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AENG 11 Engineering Shop Asst. Prof. Mark Keylord S. Onal
CNC and NC Milling can be performed under computer control. Such mills called Computer Numerical Control or Numerical Control mills are becoming increasing common in small machine shops.
ADVANTAGES OF MILLING
• • • •
Very good for one-off objects Virtually any material can be milled with a proper cutter Complex parts with high detail Tolerances of 0.001" to 0.003" are possible
DISADVANTAGES OF MILLING
•
• •
A more reduced set of features possible. Certain features are not possible More materials waste than casting type processes Quite slow
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AENG 11 Engineering Shop Asst. Prof. Mark Keylord S. Onal
BRAZING AND SOLDERING - processes employed for joining solid metal components by heating them to the proper temperature and then introducing between them a molten filler alloy (brazing metal or solder) - flux is a paste that is applied around the joint to help the brazing metal or solder to flow into the joint and to protect the metal from oxidation during the process Brazing - is a low temperature joining process - it is performed at temperatures above 840º F and it generally affords strengths comparable to those of the metal which it joins - it is low temperature in that it is done below the melting point of the base metal - it is achieved by diffusion without fusion (melting) of the base - for brazing, the most common filler metal (brazing metal) is the bronze rod.
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AENG 11 Engineering Shop Asst. Prof. Mark Keylord S. Onal
Soldering - is a low temperature joining process - it is performed at temperatures below 840ºF for joining - for soldering, the most common filler metal (solder) is an alloy of lead and tin 1) Sealing, as in automotive radiators or tin cans 2) Electrical Connections 3) Joining thermally sensitive components 4) Joining dissimilar metals
