Metalworking
Metalworking is the craft and practice of working with
metals to create parts or structures. The term covers a wide range of work-from large
ships,
bridges and
oil refineries to delicate
jewellery and instruments. Consequently, this craft covers a wide range of skills and entails the use of many types of
tools.
Today, metalworking is a trade that borders the realm of
science. Metalworking has not always been such an exacting trade, however. Metalworking had its beginnings many centuries ago. Early
humans stumbled upon metal ores on the ground , and attributed religious significance to them. Precious metals were often used as adornments in religious rituals. Later on, metals began to be used to make artifacts, including weapons. Humans slowly learned to work raw metals through trial and error. Humans learned to harness the malleability of metals.
As time progressed metal artifacts became more useful, and ever more complex. The need to further acquire and work metals grew in importance. The skill of deep
mining began to evolve, and metalsmiths became more knowledgable. Metalsmiths became important members of society. Later, the fates of entire civilizations were decided by the availability of metals and metalsmiths.
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A manual milling machine with digital readouts |
Milling is generally done on a
milling machine, which is a power-driven machine used for the complex shaping of metal (or possibly other materials) parts, by removing unneeded material to form the final shape. Its basic form is that 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,
rebating,
routing, etc. Two common types of millers are the horizontal miller and vertical miller.
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Conventional metalworking lathe |
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. 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.
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 engineers
plan to the workpiece in preparation for the next step, machining or manufacture.
Metal cutting is preformed in various ways. There are many technologies availible to cut metal.
Laser,
plasma cutting,
water jet, and good old fashioned hand cutting.
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Three different types and sizes of taps |
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 tools 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.
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. This is in contrast with
soldering and
brazing, which involve melting a lower-melting-point material between the workpieces to form a bond between them.
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.
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 not be as efficient (time wise) as 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.
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Flick grinder with magnetic chuck |
Grinding uses an
abrasive process to remove material from the workpiece. A
grinding machine is a
machine tool used for producing very fine finishes or making very light cuts, using an
abrasive wheel as the cutting device. This wheel can be made up of various sizes and types of stones,
diamonds or of
inorganic materials.
