Metalworking
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Metalworking is the craft and practice of working with metals to create individual parts, assemblies, or large scale structures. The term covers a wide range of work from large ships, bridges and oil refineries to delicate jewelery. It therefore includes a correspondingly wide range of skills and the use of many different types of metalworking processes and their related tools.
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[edit] History
Metalworking is an art, hobby, industry, and trade. It relates to metallurgy, a science, jewelery making, an art-and-craft, and as a trade and industry with ancient roots spanning all cultures and civilizations. Metalworking had its beginnings millennia in the past. Early humans, we speculate, realized different stones had different properties. These were freed metal ores on the earth's surfaces. We can further speculate that some indigenous groups attributed magical and spiritual significance to them. At some imprecise point humankind discovered that these lustrous rocks were meltable, and ductile and able to be formed into various articles for tools, adornment and practical uses. Humans over the millennia learned to work raw metals into objects of art, adornment, trade and practicality.
By the historical periods of the Pharaohs in Egypt, the Vedic Kings in India, and the Tribes of Israel, and Mayan Civilization in North America among other ancient populations, precious metals began to have value attached to them, and in some cases rules for ownership, distribution, and trade were created, enforced and agreed upon by respective peoples. By the above periods skills at creating objects of adornment, religious artifacts, and trade instruments of precious metals (non-ferrous), as well as weaponry usually of ferrous metals and/or alloys were finely honed and flawlessly executed skills and techniques practiced by artisans, blacksmiths, atharvavedic practitioners, alchemists, and other categories of metalworkers around the globe. For example, the ancient technique of granulation is found spontaneously around the world in numerous ancient cultures before the historic record shows people traveled seas or overland to far regions of the earth to share this process still being used, and attempted by metalsmiths today.
As time progressed metal objects became more common, and ever more complex. The need to further acquire and work metals grew in importance. Skills related to extracting metal ores from the earth began to evolve, and metalsmiths became more knowledgeable. Metalsmiths became important members of society. Fates and economies of entire civilizations were greatly affected by the availability of metals and metalsmiths. Today modern mining practices are more efficient, and conversely more damaging to the earth, and the workers that are engaged in the industry. Those that finance the operations are driven by profits per ounce of extracted precious metals and today's gold market which as of the date of this editing, are at a 25 year high. The metalworker though depends on the extraction of precious metals to make jewelery, build more efficient electronics, and for industrial and technological applications from construction to shipping containers to rail, and air transport. Without metals, goods and services would cease to move around the globe on the scale we know today. More individuals then ever before are learning metalworking as a creative outlet in the forms of jewelery making, hobby restoration of aircraft and cars, blacksmithing, tinsmithing, tinkering, and in other art and craft pursuits. Trade schools continue to teach welding in all of its forms, and there is a proliferation of schools of Lapidary and Jewelers arts and sciences at this- the beginning of the 21st. Century a.c.e./a.d.
[edit] General metalworking processes
Metalworking generally is divided into the following categories, forming, cutting, and, joining. Each of these categories contain various processes.
[edit] Forming processes
These processes modify the shape of the object being formed, without removing any material.
Forming is a collection of processes wherein the metal is rearranged into a specified geometry (shape) by:
- heating until molten, poured into a mold, and cooled,
- heating until the metal becomes plastically deformable by application of mechanical force,
- by the simple application of mechanical force.
Casting is an example of achieving a specific form by pouring molten metal into a mold and allowing it to cool. Hot forging is an example of moving heated metal into a specific form by deforming it with tools such as hammers or hydraulic presses while the material is at forging temperature. Drawing copper wire to a specific size is an example of forming by the use of mechanical tooling and mechanical force.
[edit] Casting
- Sand casting
- Shell casting
- Investment casting (called Lost wax casting in art)
- Die casting
- Spin casting
[edit] Plastic deforming
[edit] Powder forming
[edit] Sheet metal forming
- Bending :A calculated deformation of the metal from it original shape.
- Drawing
- Pressing
- Spinning
- Flow turning
- Roll forming
- Wheeling using an English wheel / Wheeling machine
[edit] Cutting processes
[edit] Cutting
Cutting is a collection of processes wherein material is brought to a specified geometry by removing excess material using various kinds of tooling leaving a finished part matching a set of specifications. The net result of cutting is two products, the waste or excess material, and the finished part. If this was a discussion of woodworking, the waste would be sawdust and excess wood. In cutting metals the waste is chips or swarf and excess metal. These processes can be divided into chip producing cutting, generally known as machining, burning, generally thought of as a welding process, and miscellaneous specialty processes such as chemical milling.
Cutting is nearly fully represented by:
- Chip producing processes most commonly known as machining
- Burning, a set of processes which cut by oxidizing a kerf to separate pieces of metal
- Specialty processes
Drilling a hole in a metal part is the most common example of a chip producing process. Using an oxy-fuel cutting torch to separate a plate of steel into smaller pieces is an example of burning. Chemical milling is an example of a specialty process that removes excess material by the use of etching chemicals and masking chemicals.
There are many technologies available to cut metal. Sawing, chisel, shearing, burning by Laser, gas jet and plasma, erosion by water jet or electric discharge, and hand cutting. Cutting fluid or coolant are introduced by a spray across the face of the tool and piece to decrease the temperature caused by friction and to prevent tool point weld.
[edit] Milling
Milling is the complex shaping of metal (or possibly other materials) parts, by removing unneeded material to form the final shape. It is generally done on a milling machine, a power-driven machine that in its basic form is comprised of a milling cutter that rotates about the spindle axis (like a drill), and a worktable that can move in multiple directions (usually three dimensions [x,y,z axis] relative to the workpiece, whereas a drill can only move in one dimension [z axis] while cutting). The motion across the surface of the workpiece is usually accomplished by moving the table on which the workpiece is mounted, in the x and y directions. Milling machines may be operated manually or under computer numerical control (CNC), and can perform a vast number of complex operations, such as slot cutting, planing, drilling and threading, rabbeting, routing, etc. Two common types of millers are the horizontal miller and vertical miller.
[edit] Turning and threading
A lathe is a machine tool which spins a block of material so that when abrasive, cutting, or deformation tools are applied to the workpiece, it can be shaped to produce an object which has rotational symmetry about an axis of rotation, called Solids of Revolution. Examples of objects that can be produced on a lathe include candlestick holders, table legs, bowls, baseball bats, crankshafts or camshafts.
The material may be held in place by a chuck or worked between one or two centers of which at least one can be moved horizontally to accommodate varying material lengths. In a metalworking lathe, metal is removed from the workpiece using a hardened cutting tool which is usually fixed to a solid moveable mounting called the "toolpost", this arrangement is then moved around the workpiece using handwheels and/or computer controlled motors. The main difference between the Milling Machine and the Lathe is that in the Milling Machine the tool is moving but in the Lathe, the work is moving. Modern CNC lathes can do secondary operations like milling in X,Y,Z direction by using driven tools also called live tools. When driven tools are used the work piece stops rotating and the driven tool executes the machining operation with a rotating cutting tool. Driven tools increase machining performance as all operations can be made in one set up in the CNC lathe.
[edit] Drilling and tapping
Drilling is the process of using a drill bit in a drill to produce holes. Under normal usage, swarf is carried up and away from the tip of the drill bit by the fluting. The continued production of chips from the cutting edges pushes the older chips outwards from the hole. This continues until the chips pack too tightly, either because of deeper than normal holes or insufficient backing off (removing the drill slightly [breaking the chip] or totally from the hole [clearing the bit] while drilling). Lubricants (or coolants) (i.e. cutting fluid) are sometimes used to ease this problem and to prolong the tool's life by cooling, lubricating the tip and improving chip flow.
Taps and dies are tools commonly used for the cutting of screw threads in metal parts. A tap is used to cut a female thread on the inside surface of a predrilled hole, while a die cuts a male thread on a preformed cylindrical rod.
[edit] Grinding
Grinding uses an abrasive process to remove material from the workpiece. A grinding machine is a machine tool used for producing very fine finishes, making very light cuts, or high precision forms using a abrasive wheel as the cutting device. This wheel can be made up of various sizes and types of stones, diamonds or inorganic materials.
The simplest grinder is a bench grinder or a hand-held angle grinder, for deburring parts or cutting metal with a zip-disc.
Grinders have increased in size and complexity with advances in time and technology. From the old days of a manual toolroom grinder sharpening endmills for a production shop, to today's 30000rpm CNC auto-loading manufacturing cell producing jet turbines, grinding processes vary greatly.
Grinders need to be very rigid machines to produce the required finish. Some grinders are even used to produce glass scales for positioning CNC machine axis. the common rule is the machines used to produce scales be 10 times more accurate than the machines the parts are produced for.
In the past grinders were used for finishing operations only because of limitations of tooling. Modern grinding wheel materials and the use of industrial diamonds or other made-made coatings (cubic boron nitride) on wheel forms have allowed grinders to achieve excellent results in production environments instead of being relegated to the back of the shop.
Modern technology has advanced grinding operations to include CNC controls, high material removal rates with high precision, lending itself well to aerospace applications and high volume production runs of precision components.
[edit] Joining processes
[edit] Welding
Welding is a fabrication process that joins materials, usually metals or thermoplastics, by causing coalescence. This is often done by melting the workpieces and adding a filler material to form a pool of molten material that cools to become a strong joint, but sometimes pressure is used in conjunction with heat, or by itself, to produce the weld.
Many different energy sources can be used for welding, including a gas flame, an electric arc, a laser, an electron beam, friction, and ultrasound. While often an industrial process, welding can be done in many different environments, including open air, underwater and in space. Regardless of location, however, welding remains dangerous, and precautions must be taken to avoid burns, electric shock, poisonous fumes, and overexposure to ultraviolet light.
[edit] Brazing
Brazing is a joining process in which a filler metal is melted and drawn into a capillary formed by the assembly of two or more work pieces. The filler metal reacts metallurgically with the workpiece(s) and solidifies in the capillary, forming a strong joint. Unlike welding, the work piece is not melted. Brazing is similar to soldering, but occurs at temperature higher than 840F. Brazing has the advantage of producing less thermal stresses than welding, and brazed assemblies tend to be more ductile than weldments because alloying elements can not segregate and precipitate.
Brazing techniques include, flame brazing, resistance brazing, furnace brazing, diffusion brazing, and inductive brazing.
[edit] Soldering
Soldering is a joining process that occurs at temperatures below 840 degrees Farenheit. It is similar to brazing in the fact that a filler is melted and drawn into a capillary to form a join, although at a lower temperature. Because of this lower temperature and different alloys used as fillers, the metallurgical reaction between filler and work piece is minimal, resulting in a weaker joint.
[edit] Hand fabrication
A wide variety of hand and small power tools are often used for metalworking, and an experienced machinist can fabricate almost any part using only hand tools, although it may require more time than with advanced machinery. Many types of hand tools are used, including cutting and scraping tools to remove metal, impact tools to reshape metal, and a wide variety of tools for marking, positioning, or otherwise assisting the fabrication process.
Ball-peen hammer • C-clamp • Clamp • Combination square • Die grinder • Drift pin • F-clamp • File • File card • Hacksaw • Hammer • Hand scraper • Machinist square • Magnetic base • Pliers • Power tool • Punch • Rotary tool • Saw piercing • Scriber • Tap and die • Throatless shear • Tongs • Tube and pipe benders • Vise • Workbench • Wrench
[edit] Preparation and validation
[edit] Marking out
Marking out (also known as layout) is the process of transferring a design or pattern to a workpiece and is the first step in the handcraft of metalworking. It is performed in many industries or hobbies, although in the repetition industries the need to mark out every individual piece is eliminated.
In the metal trades area, marking out consists of transferring the engineer's plan to the workpiece in preparation for the next step, machining or manufacture.
[edit] External links
- Metal Matters online exhibit from the Smithsonian Institution.
- Society of American Silversmiths
- Society of Manufacturing Engineers
- Machinist journal News, Case studies for machinists
- Modern Machine tools Machine tool Blog
- Elementary Knowledge of Metalworking
Image:Blacksmith-hammer-anvil-50x50.png Metalworking | |
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| Metalworking topics | Casting • CNC • Cutting tools • Drilling and threading • Fabrication • Forging • Grinding • Jewellery • Lathe • Machining • Machine tooling • Measuring • Metalworking • Hand tools • Metallurgy • Milling • Occupations • Press tools • Pipe and Tube bending • Smithing • Terminology • Welding |
es:Metalurgia hr:Metalurgija it:Metalmeccanica nl:Metaalbewerking ja:金属加工
