Sheet metal is metal formed by an industrial process into thin, flat pieces. Sheet metal is one of the fundamental forms used in metalworking and it can be cut and bent into a variety of shapes. Countless everyday objects are fabricated from sheet metal. Thicknesses can vary significantly. Sheet metal is available in coiled strips; the coils are formed by running a continuous sheet of metal through a roll slitter. In most of the world, sheet metal thickness is specified in millimeters. In the US, the thickness of sheet metal is specified by a traditional, non-linear measure known as its gauge; the larger the gauge number, the thinner the metal. Used steel sheet metal ranges from 30 gauge to about 7 gauge. Gauge differs between nonferrous metals such as aluminum or copper. Copper thickness, for example, is measured in ounces. Parts manufactured from sheet metal must maintain a uniform thickness for ideal results. There are many different metals that can be made into sheet metal, such as aluminium, copper, tin and titanium.
For decorative uses, some important sheet metals include silver and platinum Sheet metal is used in automobile and truck bodies, airplane fuselages and wings, medical tables, roofs for buildings and many other applications. Sheet metal of iron and other materials with high magnetic permeability known as laminated steel cores, has applications in transformers and electric machines. An important use of sheet metal was in plate armor worn by cavalry, sheet metal continues to have many decorative uses, including in horse tack. Sheet metal workers are known as "tin bashers", a name derived from the hammering of panel seams when installing tin roofs. Hand-hammered metal sheets have been used since ancient times for architectural purposes. Water-powered rolling mills replaced the manual process in the late 17th century; the process of flattening metal sheets required large rotating iron cylinders which pressed metal pieces into sheets. The metals suited for this were lead, zinc and steel. Tin was used to coat iron and steel sheets to prevent it from rusting.
This tin-coated sheet metal was called "tinplate." Sheet metals appeared in the United States in the 1870s, being used for shingle roofing, stamped ornamental ceilings and exterior facades. Sheet metal ceilings were only popularly known as "tin ceilings" as manufacturers of the period did not use the term; the popularity of both shingles and ceilings encouraged widespread production. With further advances of steel sheet metal production in the 1890s, the promise of being cheap, easy to install and fireproof gave the middle-class a significant appetite for sheet metal products, it was not until the 1930s and WWII that metals became scarce and the sheet metal industry began to collapse. However, some American companies, such as the W. F. Norman Corporation, were able to stay in business by making other products until Historic preservation projects aided the revival of ornamental sheet metal. Grade 304 is the most common of the three grades, it offers good corrosion resistance while maintaining weldability.
Available finishes are #2B, #3, #4. Grade 303 is not available in sheet form. Grade 316 possesses more corrosion resistance and strength at elevated temperatures than 304, it is used for pumps, chemical equipment, marine applications. Available finishes are #2B, #3, #4. Grade 410 is a heat treatable stainless steel, but it has a lower corrosion resistance than the other grades, it is used in cutlery. The only available finish is dull. Grade 430 is popular grade, low cost alternative to series 300's grades; this is used. Common grade for appliance products with a brushed finish. Aluminum is a popular metal used in sheet metal due to its flexibility, wide range of options, cost effectiveness, other properties; the four most common aluminium grades available as sheet metal are 1100-H14, 3003-H14, 5052-H32, 6061-T6. Grade 1100-H14 is commercially pure aluminium chemical and weather resistant, it has low strength. It is used in chemical processing equipment, light reflectors, jewelry. Grade 3003-H14 is stronger than 1100, while maintaining the same low cost.
It is corrosion weldable. It is used in stampings and drawn parts, mail boxes, cabinets and fan blades. Grade 5052-H32 is much stronger than 3003, it maintains weldability. Common applications include electronic chassis and pressure vessels. Grade 6061-T6 is a common heat-treated structural aluminium alloy, it is weldable, corrosion resistant, stronger than 5052, but not as formable. It loses some of its strength, it is used in modern aircraft structures. Brass is an alloy of copper, used as a sheet metal, it has more strength, corrosion resistance and formability when compared to copper while retaining its conductivity. In sheet hydroforming, variation in incoming sheet coil properties is a common problem for forming process with materials for automotive applications. Though incoming sheet coil may meet tensile test specifications, high rejection rate is ofte
A drill is a tool used for making round holes or driving fasteners. It is fitted with either a drill or driver, depending on application, secured by a chuck; some powered drills include a hammer function. Drills vary in speed and size, they are characteristically corded electrically driven devices, with hand operated types decreasing in popularity and cordless battery powered ones proliferating. Drills are used in woodworking, machine tool fabrication and utility projects. Specially designed versions are made for medicine and miniature applications. Around 35,000 BC, Homo sapiens discovered the benefits of the application of rotary tools; this would have rudimentarily consisted of a pointed rock being spun between the hands to bore a hole through another material. This led to the hand drill, a smooth stick, sometimes attached to flint point, was rubbed between the palms; this was used by many ancient civilizations around the world including the Mayans. The earliest perforated artifacts, such as bone, ivory and antlers found, are from the Upper Paleolithic era.
Bow drill are the first machine drills, as they convert a back and forth motion to a rotary motion, they can be traced back to around 10,000 years ago. It was discovered that tying a cord around a stick, attaching the ends of the string to the ends of a stick, allowed a user to drill quicker and more efficiently. Used to create fire, bow-drills were used in ancient woodwork and dentistry. Archaeologists discovered a Neolithic grave yard in Mehrgrath, Pakistan dating from the time of the Harappans, around 7,500–9,000 years ago, containing 9 adult bodies with a total of 11 teeth, drilled. There are hieroglyphs depicting Egyptian carpenters and bead makers in a tomb at Thebes using bow-drills; the earliest evidence of these tools being used in Egypt dates back to around 2500 BCE. The usage of bow-drills was spread through Europe, Africa and North America, during ancient times and is still used today. Over the years many slight variations of bow and strap drills have developed for the various uses of either boring through materials or lighting fires.
The core drill was developed in ancient Egypt by 3000 BC. The pump drill was invented during Roman times, it consists of a vertical spindle aligned by a piece of horizontal wood and a flywheel to maintain accuracy and momentum. The hollow-borer tip, first used around the 13th century, consisted of a stick with a tubular shaped piece of metal on the end, such as copper; this allowed a hole to be drilled while only grinding the outer section of it. This separates the inner stone or wood from the rest, allowing the drill to pulverize less material to create a sized hole. While the pump-drill and the bow-drill were used in Western Civilization to bore smaller holes for a larger part of human history, the Auger was used to drill larger holes starting sometime between Roman and Medieval ages; the auger allowed for more torque for larger holes. It is uncertain when the Bit was invented, it is a type of hand crank drill. The brace, on the upper half, is where the user turns it and on the lower part is the bit.
The bit is interchangeable. The auger uses a rotating helical screw similar to the Archimedean screw-shaped bit, common today; the gimlet is worth mentioning as it is a scaled down version of an auger. In the East, churn drills were invented as early as 221 BC during the Chinese Qin Dynasty, capable of reaching a depth of 1500 m. Churn drills in ancient China were built of wood and labor-intensive, but were able to go through solid rock; the churn drill appears in Europe during the 12th century. In 1835 Isaac Singer is reported to have built a steam powered churn drill based on the method the Chinese used. Worth discussing are the early drill presses. Drill presses consisted of the powered drills that could be raised or lowered into a material, allowing for less force by the user; the next great advancement in drilling technology, the electric motor, led to the invention of the electric drill. It is credited to Arthur James Arnot and William Blanch Brain of Melbourne, Australia who patented the electric drill in 1889.
In 1895, the first portable handheld drill was created by brothers Wilhem & Carl Fein of Stuttgart, Germany. In 1917 the first trigger-switch, pistol-grip portable drill was patented by Decker; this was the start of the modern drill era. Over the last century the electric drill has been created in a variety of types and multiple sizes for an assortment of specific uses. There are many types of drills: some are powered manually, others use electricity or compressed air as the motive power, a minority are driven by an internal combustion engine. Drills with a percussive action are used in hard materials such as masonry or rock. Drilling rigs are used to bore holes in the earth to obtain oil. Oil wells, water wells, or holes for geothermal heating are created with large drilling rigs; some types of hand-held drills are used to drive screws and other fasteners. Some small appliances that have no motor of their own may be drill-powered, such as small pumps, etc. Bow - A simple rotational hand-operated tool of prehistoric origin.
Brace - A woodworker's brace has a ‘U’ formed wrench/outline, utilized to tran
Full-mold casting is an evaporative-pattern casting process, a combination of sand casting and lost-foam casting. It uses an expanded polystyrene foam pattern, surrounded by sand, much like sand casting; the metal is poured directly into the mold, which vaporizes the foam upon contact. First, a pattern is made from polystyrene foam, which can be done many different ways. For small volume runs the pattern can be hand machined from a solid block of foam. If the volume is large the pattern can be mass-produced by a process similar to injection molding. Pre-expanded beads of polystyrene are injected into a preheated aluminum mold at low pressure. Steam is applied to the polystyrene which causes it to expand more to fill the die; the final pattern is 97.5% air and 2.5% polystyrene. The finished patterns can be hot glued to pre-made pouring basins and risers to form the final pattern; the pattern is coated with a refractory material. The coated pattern is placed in a flask and packed with green sand or a chemically bonded sand.
The molten metal is poured into the mold, which vaporizes the foam allowing the metal to fill the entire mold. The vapor is extracted from the flask through the sand; the casting is allowed to cool and dumped out of the flask ready to use. The sand does not need to be reprocessed; the minimum wall thickness for a full-mold casting is 2.5 mm. Typical dimensional tolerances are 0.3% and typical surface finishes are from 2.5 to 25 µm RMS. The size range is from 400 g to several tonnes. Full-mold casting is used to produce cylinder heads, engine blocks, pump housings, automotive brake components, manifolds. Employed materials include aluminium, steel, nickel alloys, copper alloys; this casting process is advantageous for complex castings, that would require cores. It is dimensionally accurate, requires no draft, has no parting lines so no flash is formed; as compared to investment casting, it is cheaper because it is a simpler process and the foam is cheaper than the wax. Risers are not required due to the nature of the process.
The two main disadvantages are that pattern costs can be high for low volume applications and the patterns are damaged or distorted due to their low strength. If a die is used to create the patterns there is a large initial cost; the first patent for an evaporative-pattern casting process was filed in April 1956, by H. F. Shroyer, he patented the use of foam patterns embedded in traditional green sand for metal casting. Degarmo, E. Paul. Materials and Processes in Manufacturing, Wiley, ISBN 0-471-65653-4. Kalpakjian, Serope.
Crimping is joining two or more pieces of metal or other ductile material by deforming one or both of them to hold the other. The bend or deformity is called the crimp; the metals are joined together via a special connector. Stripped wire is inserted through the sized opening of the connector, a crimper is used to squeeze the opening against the wire. Depending on the type of connector used, it may be attached to a metal plate by a separate screw or bolt or it could be screwed on using the connector itself to make the attachment like an F connector. Crimping is most extensively used in metalworking. Crimping is used to fix bullets in their cartridge cases, for rapid but lasting electrical connections, securing lids on metal food cans, many other applications; because it can be a cold-working technique, crimping can be used to form a strong bond between the workpiece and a non-metallic component. When joining segments of tubular sheet metal pipe, such as for smoke pipes for wood stoves, downspouts for rain gutters, or for installation of ventilation ducting, one end of a tube is treated with a crimping tool to make a slip joint into the next section of duct.
The joint will be adequate for conveying low pressure fluids. Crimp joints may be arranged to prevent accumulation of dirt. In jewelry manufacture, crimp beads, or crimp tubes, are used to make secure joints in fine wire, such as used in clasps or tie loops. A crimped lead seal is attached to secure wires used to secure fasteners in aircraft, or to provide visual evidence of tampering when securing a utility meter or as a seal on cargo containers. Pliers
Sand casting known as sand molded casting, is a metal casting process characterized by using sand as the mold material. The term "sand casting" can refer to an object produced via the sand casting process. Sand castings are produced in specialized factories called foundries. Over 60% of all metal castings are produced via sand casting process. Molds made of sand are cheap, sufficiently refractory for steel foundry use. In addition to the sand, a suitable bonding agent occurs with the sand; the mixture is moistened with water, but sometimes with other substances, to develop the strength and plasticity of the clay and to make the aggregate suitable for molding. The sand is contained in a system of frames or mold boxes known as a flask; the mold cavities and gate system are created by compacting the sand around models called patterns, by carving directly into the sand, or by 3D printing. There are six steps in this process: Place a pattern in sand to create a mold. Incorporate the pattern and sand in a gating system.
Remove the pattern. Fill the mold cavity with molten metal. Allow the metal to cool. Break away the sand mold and remove the casting. From the design, provided by a designer, a skilled pattern maker builds a pattern of the object to be produced, using wood, metal, or a plastic such as expanded polystyrene. Sand can be ground, strickled into shape; the metal to be cast will contract during solidification, this may be non-uniform due to uneven cooling. Therefore, the pattern must be larger than the finished product, a difference known as contraction allowance. Different scaled rules are used for different metals, because each metal and alloy contracts by an amount distinct from all others. Patterns have core prints that create registers within the molds into which are placed sand cores; such cores, sometimes reinforced by wires, are used to create under-cut profiles and cavities which cannot be molded with the cope and drag, such as the interior passages of valves or cooling passages in engine blocks.
Paths for the entrance of metal into the mold cavity constitute the runner system and include the sprue, various feeders which maintain a good metal'feed', in-gates which attach the runner system to the casting cavity. Gas and steam generated during casting exit through the permeable sand or via risers, which are added either in the pattern itself, or as separate pieces. In addition to patterns, the sand molder could use tools to create the holes. A multi-part molding box is prepared to receive the pattern. Molding boxes are made in segments that may be latched to end closures. For a simple object—flat on one side—the lower portion of the box, closed at the bottom, will be filled with a molding sand; the sand is packed in through a vibratory process called ramming, in this case, periodically screeded level. The surface of the sand may be stabilized with a sizing compound; the pattern is placed on the sand and another molding box segment is added. Additional sand is rammed around the pattern. A cover is placed on the box and it is turned and unlatched, so that the halves of the mold may be parted and the pattern with its sprue and vent patterns removed.
Additional sizing may be added and any defects introduced by the removal of the pattern are corrected. The box is closed again; this forms a "green" mold. If the mold is not sufficiently dried a steam explosion can occur. In some cases, the sand may be oiled instead of moistened, which makes casting possible without waiting for the sand to dry. Sand may be bonded by chemical binders, such as furane resins or amine-hardened resins. Additive manufacturing can be used in the sand mold preparation, so that instead of the sand mold being formed via packing sand around a pattern, it is 3D-printed; this can reduce lead times for casting by obviating patternmaking. Besides replacing older methods, additive can complement them in hybrid models, such as making a variety of AM-printed cores for a cavity derived from a traditional pattern. To control the solidification structure of the metal, it is possible to place metal plates, chills, in the mold; the associated rapid local cooling will form a finer-grained structure and may form a somewhat harder metal at these locations.
In ferrous castings, the effect is similar to quenching metals in forge work. The inner diameter of an engine cylinder is made hard by a chilling core. In other metals, chills may be used to promote directional solidification of the casting. In controlling the way a casting freezes, it is possible to prevent internal voids or porosity inside castings. To produce cavities within the casting—such as for liquid cooling in engine blocks and cylinder heads—negative forms are used to produce cores. Sand-molded, cores are inserted into the casting box after removal of the pattern. Whenever possible, designs are made that avoid the use of cores, due to the additional set-up time and thus greater cost. With a completed mold at the appropriate moisture content, the box containing the sand mold is positioned for filling with molten metal—typically iron, bronze, aluminium, magnesium alloys, or various pot metal alloys, which include lead and zinc. After being filled with liquid metal the box is set aside until the metal is sufficiently cool to be strong.
The sand is removed, revealing a rough casting that, in the case of iron or steel, may still be glowing red. In the case of metals that are heavier than the casting sand, such as iron or lead, the casting flask is cover
Lost-foam casting is a type of evaporative-pattern casting process, similar to investment casting except foam is used for the pattern instead of wax. This process takes advantage of the low boiling point of polymer foams to simplify the investment casting process by removing the need to melt the wax out of the mold. First, a pattern is made from polystyrene foam. For small volume runs the pattern can be hand machined from a solid block of foam. If the volume is large the pattern can be mass-produced by a process similar to injection molding. Pre-expanded beads of polystyrene are injected into a preheated aluminum mold at low pressure. Steam is applied to the polystyrene which causes it to expand more to fill the die; the final pattern is 97.5% air and 2.5% polystyrene. Pre-made pouring basins and risers can be hot glued to the pattern to finish it. Next, the foam cluster is coated with ceramic investment known as the refractory coating, via dipping, spraying or flow coating. After the coating dries, the cluster is placed into a flask and backed up with un-bonded sand, compacted using a vibration table.
The refractory coating captures all of the detail in the foam model and creates a barrier between the smooth foam surface and the coarse sand surface. Secondly it controls permeability, which allows the gas created by the vaporized foam pattern to escape through the coating and into the sand. Controlling permeability is a crucial step to avoid sand erosion, it forms a barrier so that molten metal does not penetrate or cause sand erosion during pouring. Once the sand is compacted, the mold is ready to be poured. Automatic pouring is used in LFC, as the pouring process is more critical than in conventional foundry practice. There is no bake-out phase, as for lost-wax; the melt is poured directly into the foam-filled mold. As the foam is of low density, the waste gas produced by this is small and can escape through mold permeability, as for the usual outgassing control. Cast metals include cast irons, aluminium alloys and nickel alloys; the size range is from 0.5 kg to several tonnes. The minimum wall thickness is 2.5 mm and there is no upper limit.
Typical surface finishes are from 2.5 to 25 µm RMS. Typical linear tolerances are ±0.005 mm/mm. This casting process is advantageous for complex castings that would require cores, it is dimensionally accurate, maintains an excellent surface finish, requires no draft, has no parting lines so no flash is formed. The un-bonded sand of lost foam casting can be much simpler to maintain than green sand and resin bonded sand systems. Lost foam is more economical than investment casting because it involves fewer steps. Risers are not required due to the nature of the process. Foam is easy to manipulate and glue, due to its unique properties; the flexibility of LFC allows for consolidating the parts into one integral component. The two main disadvantages are that pattern costs can be high for low volume applications and the patterns are damaged or distorted due to their low strength. If a die is used to create the patterns there is a large initial cost. Lost-foam casting was invented in the early fifties by Canadian sculptor Armand Vaillancourt.
Public recognition of the benefits of LFC was made by General Motors in the mid 1980s when it announced its new car line, would utilize LFC for production of all engine blocks, cylinder heads, differential carriers, transmission cases. Full-mold casting Degarmo, E. Paul. Materials and Processes in Manufacturing, Wiley, ISBN 0-471-65653-4. Kalpakjian, Serope.
In metalworking and jewellery making, casting is a process in which a liquid metal is somehow delivered into a mold that contains a hollow shape of the intended shape. The metal is poured into the mold through a hollow channel called a sprue; the metal and mold are cooled, the metal part is extracted. Casting is most used for making complex shapes that would be difficult or uneconomical to make by other methods. Casting processes have been known for thousands of years, have been used for sculpture, jewellery in precious metals, weapons and tools. Traditional techniques include plaster mold casting and sand casting; the modern casting process is subdivided into two main categories: expendable and non-expendable casting. It is further broken down by the mold material, such as sand or metal, pouring method, such as gravity, vacuum, or low pressure. Expendable mold casting is a generic classification that includes sand, shell and investment moldings; this method of mold casting involves the use of non-reusable molds.
Sand casting is one of the most popular and simplest types of casting, has been used for centuries. Sand casting allows for smaller batches than permanent mold casting and at a reasonable cost. Not only does this method allow manufacturers to create products at a low cost, but there are other benefits to sand casting, such as small-size operations; the process allows for castings small enough fit in the palm of one's hand to those large enough only for train beds. Sand casting allows most metals to be cast depending on the type of sand used for the molds. Sand casting requires a lead time of days, or weeks sometimes, for production at high output rates and is unsurpassed for large-part production. Green sand, black in color, has no part weight limit, whereas dry sand has a practical part mass limit of 2,300–2,700 kg. Minimum part weight ranges from 0.075–0.1 kg. The sand is bonded together using chemical binders, or polymerized oils. Sand requires little maintenance. Plaster casting is similar to sand casting except that plaster of paris is used instead of sand as a mold material.
The form takes less than a week to prepare, after which a production rate of 1–10 units/hr-mold is achieved, with items as massive as 45 kg and as small as 30 g with good surface finish and close tolerances. Plaster casting is an inexpensive alternative to other molding processes for complex parts due to the low cost of the plaster and its ability to produce near net shape castings; the biggest disadvantage is that it can only be used with low melting point non-ferrous materials, such as aluminium, copper and zinc. Shell molding is similar to sand casting, but the molding cavity is formed by a hardened "shell" of sand instead of a flask filled with sand; the sand used is finer than sand casting sand and is mixed with a resin so that it can be heated by the pattern and hardened into a shell around the pattern. Because of the resin and finer sand, it gives a much finer surface finish; the process is automated and more precise than sand casting. Common metals that are cast include cast iron, aluminium and copper alloys.
This process is ideal for complex items. Investment casting is a process, practiced for thousands of years, with the lost-wax process being one of the oldest known metal forming techniques. From 5000 years ago, when beeswax formed the pattern, to today’s high technology waxes, refractory materials and specialist alloys, the castings ensure high-quality components are produced with the key benefits of accuracy, repeatability and integrity. Investment casting derives its name from the fact that the pattern is invested, or surrounded, with a refractory material; the wax patterns require extreme care for they are not strong enough to withstand forces encountered during the mold making. One advantage of investment casting is; the process is suitable for repeatable production of net shape components from a variety of different metals and high performance alloys. Although used for small castings, this process has been used to produce complete aircraft door frames, with steel castings of up to 300 kg and aluminium castings of up to 30 kg.
Compared to other casting processes such as die casting or sand casting, it can be an expensive process. However, the components that can be produced using investment casting can incorporate intricate contours, in most cases the components are cast near net shape, so require little or no rework once cast. A durable plaster intermediate is used as a stage toward the production of a bronze sculpture or as a pointing guide for the creation of a carved stone. With the completion of a plaster, the work is more durable than a clay original which must be kept moist to avoid cracking. With the low cost plaster at hand, the expensive work of bronze casting or stone carving may be deferred until a patron is found, as such work is considered to be a technical, rather than artistic process, it may be deferred beyond the lifetime of the artist. In waste molding a simple and thin plaster mold, reinforced by sisal or burlap, is cast over the original clay mixture; when cured, it is removed from the damp clay