PERCUSSIVE TOOLS

Post 604 by Gautam Shah 

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Percussive word derives from (Latin 1735) percuss, past participle stem of percutere. Percussive is a motion formed by striking, such as a beating, pounding or hammering, versus just vibration. In phonetics it is the sound of smacking the lips or gnashing the teeth. Percussive dances have highly rhythmic movement like tapping feet, clapping, or finger snapping, etc.

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Percussive tools deliver concentrated blows or impact. The delivery is in swift motion at specific location generating or transmitting a force. The tools can have ‘a nonspecific end’ or sharper point or edge as specific function end. The self weight of the impacting end delivers the mass, and the holding arm or the tool handle adds to the momentum while controlling the velocity. The ‘sharpness’ of the impact is determined by the type of task, which in turn is defined by the deformation required in the material. To beat flour dough or wet clay requires very little force, but to deform copper or iron greater impact is required.

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Roof-slate workers hammer > Wikipedia image by Antoine Taveneaux

The percussive hand tools operate on circular motion, where the handle or arm form a swinging arc to deliver the blow. In hand tools the length of an axis (radius) is formed by the combined measures of the handle and the operative arm. In case of machines, the handle is the ‘arm’. Percussive tools also use the pull of the gravity as a work force, such as for driving piles for foundation work.

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Old Australian Logging axes > Wikipedia image by Fir0002 at en.wikipedia

Percussive tools have been of basic two types: The impacting ones with own head formations (axes pounder, beetle, mallet, maul, pestle, sledge, or with separate work points or edges. Percussive tools work as combination of head weight and handle length. Different combinations are used for craft to industrial work. Goldsmiths use light-head and long-armed hammers. A stone mason uses a heavy metal-head and small handle. For metal forging, the hammers have heavy-head and long-arm. A long handle, even if not needed for impact, it helps to control the blows reduces work fatigue. Soft headed percussive tools are used for sheet metal fabrication, painted elements, fabric levelling, etc.

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Spears and Handles > Wikipedia image

HAMMERS: A hammer is a striking tool also known as a pounder, beetle, mallet, maul, pestle, sledge, etc. There are many trade specific hammers, like, the carpenter’s claw type, smith’s rivetting, boiler-maker’s, bricklayer’s, blacksmith’s, machinist’s ball peen and cross peen, goldsmiths’, smith’s stone (or spalling), prospecting, and tacks hammer. Each hammer has a distinctive form, with minor variations in terms of weight, length and angle of the handle, and the shape of the face. A pounder, or hammer stone, was the first tool to have a handle, marking a great technological advance. A long handle, even if not needed for dynamic effect (as in a tool used only for light blows), makes the tool easier to control and generally reduces operators’ fatigue. Club like pounders or mallet, with handles of the same material are widely used. The hammer as a tool, for nailing, rivetting, and smithing, originated in the Metal Age. For beating lumps of metal into strips and sheet, heavy and compact hammers with flat faces are needed, whereas lighter ones are more suited to rivetting and driving nails and wooden pegs.

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Few Hammer heads > Flickr image by denise carbonell

Hammers with dual heads are in use since Roman age. Hammers with dual heads include: clawed hammers for pulling out nails, hammers with a chisel or pointed ends to dig out shafts, toothed edges to smoothen the stone surfaces. Other special forms of the peen (-the end opposite the flat face) like hemispherical, round-edged, and wedge like shapes helped the metalworker stretch and bend metal or the mason to chip or break stone or bricks. A file maker’s hammer has two chisel-like heads, to score flat pieces of lead (file blanks) that were subsequently hardened by heating and quenching. Heavy hammers are used as part of power tools, and largest are the pile drivers. Trip-hammers are gravity impulse based but steam hammers use, besides gravity a downward thrust from a steam-pushed piston. Pneumatic hammers driven by air include the hammer drill, used on rock and concrete. The rivetting hammer is used in steel construction with girders and plates.

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Forging hammer > Wikipedia image by Vitold Muratov

Hammers’ heads are meant to impact the task pieces by striking over the head of a chisel, nails, shank, pins, bars, shaping dies, etc.

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Forging gang > Wikipedia image by Lord van Tasm

 CHISELS: Chisels have been the chief cutting tools often combined with a hammering device. Chipped flints were used in 8000 BC, till neolithic period. Rectangular flint and obsidian chisels were used on soft stone and timber. Chisels with concave heads were used to create deeper sections. Chisels and gouges of very hard stone were used to dig out the bowls out of soft stones such as alabaster, gypsum, soapstone, and volcanic rock. The earliest copper and bronze chisels were long compared to flint chisels, and were used by the Egyptians to dress limestone and sandstone for their monuments. Use of wooden handles saved the chisel metal to half length, while causing less damage to the mallet. The chisel has since then taken on many shapes, and is being put to many different uses.

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Hammering leather book for Gold leaf making Mandalay Myanmar > Wikipedia image by Adam Jones

Modern day machines incorporate percussive processes. Forging workshops use automatic forging machines. Construction sites use pneumatic pile driving devices. Industrial presses use percussion as metal cutting, shaping, forming device. Stamping machine impact shaping or forming dies to generate a shaped product like coins. Gold foil makers beat small pieces of gold between layers of leathers.

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Cricket bat a striking or percussive device > Street cricket Agra Uttar Pradesh India Flicker image by John Haslam

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MACHINE TOOLS and MACHINES

Post 297 – by Gautam Shah

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Machine tools are power driven utilities, and are of two basic types: Hand held or mobile tools and Stationary tools. Hand-held tools are apparently small, and lightweight. Whereas stationary tools often called, Machine tools, are large, fixed to a position. The large size requires stationary positioning. Both types of machine tools are classifiable into home or hobby machine tools and Industrial or Engineering machine tools.

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Machines and machine tools both are automated entities, and so have slightly overlapping categorization. A machine is a specific product entity which can be conducting several sequential or concurrent processes. A machine tool is a multi-purpose entity, and used for several processes. It can have attachments of (non-machine) tools, or it may be part of a machine. All machine-tools are a type of machine, but conversely all machines may not be called machine tools. To use a tool or machine tools some form adaptation, recognized as craftsmanship is required. Machines do not need personal creativity or craftsmanship except basic technical knowledge.

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Machines and machine tools are powered by human, animal, kinetic, hydraulic and pneumatic power, wind mills, steam and electric power. Machine tools need to be manipulated or the feed-stock requires positioning, adjustment, etc. When this input processes are guided or automated, a machine tool becomes a machine. The guidance or automation may be to free the hands, other limbs and sensory nodes. So, in this sense a machine can have several machine tools, each of which has time-space feeds mechanisms. Advance machines have feed-forward and feed back systems to reduce or correct errors.

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A machine-tool can take up various types of tools. Such as a drill can take different types of bits or a potter uses different shapes of spatulas to shape and finish the turned-clay item. A CNC machine, has predefined set of feed-guide processes controlled by the computer input. A machine tool that is handy will have to be very quite and vibration free. Very fine work tools like a dentist or orthopaedic surgical drills are operated through pneumatic or compressed air, rather then electric motors. The pneumatic technology offers vibration free and noiseless movement at very high speeds. Similarly Air-jet looms working on suction reduce the nominal noise associated with yarn bobbin shuttles.

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Machines were stationary entities due to the robust size, stability and power needs. This created batch production system, creating lots of cross traffic within the plant. Batch production with fixed machines required power locally. This was difficult proposition when steam or a large electric motor generated power was transferred through shafts and belts to the machine. Batch based products tended to be holistic in nature. The need for faster production forced rethinking of product design into component-based entities. Components were produced by machine tools or machines and brought to the assembly line. The assembly line was operated through handy machine tools.

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Assembly lines had many grey areas. A slowdown or stoppage affected the entire production systems. Processes, tasks, etc., were carefully apportioned in terms duration, speed and space. All these studies provided opportunities for automation of assembly processes. The automation allowed multiple operation at a station which drastically reduced the length of assembly lines. The automation is now seen in use of robots handling several processes at a station. A human assembler cannot go into narrow spaces, take difficult body postures and require rest or diversion, but a robot is beyond these difficulties. A robot is a machine with several machine tools.

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HAMMERS

Post by –Gautam Shah

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A hand tool is an instrument of various forms and purposes, traditionally operated by the muscular power of the user. Major section of hand Tools are of Percussive variety. These tools are used to deliver blows such as axes, adz, and hammers, etc. Other varieties include cutting, drilling, and abrading tools such as the knife, awl, drill, saw, file, chisel, and plane.

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Dent repair tools Image from Photobucket.com/user/afazz65/media/tools/drawer18

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Carvers hammers of wood > Flickr image by Danny Ayers

Percussive tools deliver concentrated blows or impact in swift motion and so are also called dynamic tools. The prime tools in this category are the Axe and Hammer. An axe is a cutting tool, but it has been used for striking, so a percussive tool.

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Ancient tied Stone head hammers

HAMMERING TOOLS

A hammer is a striking tool also known as a pounder, beetle, mallet, maul, pestle, sledge, etc. There are many trade specific hammers, like, the carpenter’s claw type, smith’s riveting, boiler-maker’s, bricklayer’s, blacksmith’s, machinist’s ball peen and cross peen, goldsmiths’, smith’s stone (or spalling), prospecting, and tack hammers.

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Wood Hammer > Wikipedia image by Johan (GFDL)

Each hammer has a distinctive form, with minor variations in terms of weight, length and angle of the handle, and the profile of the face. A pounder, or hammer stone, was the second tool, after the axe to have a handle, marking a great technological advance. A long handle, is needed for striking effect such as in a tool used for light blows. It makes the tool easier to control, and generally reduces operators’ fatigue.

Splitting maul

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Stockhammer > Wikipedia Image by Reiner Flassig

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Forge trip hammer > wikipedia image by William F. Durfee

Club like pounders or mallet, with a handle of the same as well as different materials are widely used. The hammer as a tool, for nailing, riveting, and smiting, originated in the Metal Age. For beating lumps of metal into strips and sheet, heavy and compact hammers with flat faces are needed, whereas lighter ones are more suited to riveting and driving nails and wooden pegs.

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Old Pick Hammer > Wikipedia image by Vassil

Hammers with dual heads are in use since Roman age. Hammers with dual heads include, clawed hammers for pulling out nails, hammers with a chisel or pointed ends to dig out shafts, toothed edges to smoothen the stone surfaces. Other special forms of the peen (-the end opposite the flat face) like hemispherical, round edged, and wedge like shapes helped the metalworker stretch and bend metal or the mason to chip or break stone or bricks.

Hammer for upholstery work

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from a catalogue of suppliers to watchmakers and jewelers

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Ritual hammers from Early Bronze age to II Mil BC

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Dressing Hammer > Wikipedia image by Rasbak

A file maker’s hammer has two chisel-like heads, to score flat pieces of lead (file blanks) that are subsequently hardened by heating and quenching. Heavy hammers are used as part of power tools, and largest are the pile drives for foundation work. Trip-hammers are gravity impulse based but steam hammers use, besides gravity a downward thrust from a steam-pushed piston.

Pneumatic hammers are driven by air and include the hammer drill used for work on rock and concrete. The rivetting hammer is used in steel construction for flattening rivet heads over girders and plates.

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Pounding Rice Cake in Korea > Image by Cornell University @ Flickr Commons

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Making Rice Cakes > Flickr Image by A. Davey

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DRILLING

Postby Gautam Shah

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Drilling is a very old craft practised by various civilizations. Historically materials like shell, ivory, antler, bones, tooth and baked ceramics, have been pierced through to make adornments. Means and methods for drilling of hard materials like stones, glasses, metals, nodules and beads were developed by ancient people. Soft materials like skins (hides, leather) were punched for stitching or tying.

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Deep-set teeth like wisdom (third molar) of live patients were drilled during 7000 and 5500 BC. Skulls with signs of trepanation have been found in prehistoric human remains from Neolithic times onward. Trepanning, (trephination, trephining) or making a burr hole is probably the oldest surgical procedure, dating 40,000 years. It is a surgical intervention in which a hole is drilled or scraped into the human skull to cure epileptic seizures, migraines, and mental disorders. It was also done to remove shattered bits of bone from a fractured skull and clean out the blood that often pools under the skull after a head injury.

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Drills have been used for producing new holes, enlarging existing holes and also for shaping cavities to various forms of sections. Drills with special attachments are also used for creating threads inside cylindrical forms. Shallow depth drilling has been used for etching, engraving and carving on very hard surfaces like obsidian and for material removing and surface polishing.

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About 110,000 years back Neanderthal man began to use many different types of handled tools like axes, borers, knives and spears. In all these tools, the edges were heavily notched (due to chipping of the stone) but a toothed edge helped in carving, cutting and boring processes for materials like horn, bone, skins, wood, stones, etc. Wood, natural fibres and bones complimented the edge stones for handling and gripping. Approximately 35 000 years back, Cro-Magnon man devised newer tools. Burin, an engraving tool, was made from a sharp narrow flint blade, for incising and burrowing. This made it possible to work the horn and bone into combs, needles, beads and such other small items. Tools similar to a burin were used for cleaning and shaving hides.

Flint blades slimmed to a sharp point were used for piercing holes. Another method could have been to grind a hole with abrasive sand under the point of a stick. Diamond points (‘jeweled’) were used as drilling bits.

The Egyptians invented the circular trephine, made by of a tube with serrated borders (similar to the country tool used for punching a large size hole in masonry structure). It gives a round disk like cut called ‘crown’. The crown cut was worn by the patient to ward off evil.

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An awl and the needle were the first hole making tools. These create a hole by shifting or compressing the material to sides rather than removing it. Small, shallow holes in stone, concrete, brick, and similar materials are usually drilled by a hand star punch, (a steel rod with an X-shaped cutting point, which was held against the object to be holed and struck with a hammer or sledge while revolving slightly after each stroke). A hardened metal punch is used even today to push a hole in fragile materials like plaster, bricks. Paper leather, etc. Punch is also used to mark a small indentation, so that drilling bit has a homing mark. Metal sheets cannot be drilled properly so are holed by a pointed punch or a punching die.

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The bow drill is an ancient form of drilling tools. It was commonly used to make fire, and was also called a fire drill. However, the same principle also was used widely in drilling for wood and teeth. Bow drills were used since 4th C. BC to drill holes into lapis lazuli and cornelian.

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Augers are large size hole making tools. Initially in the Iron Age it was a simple cutting bar or plate joined at a right angle to an axle which could be rotated. Later it was like a short length split pipe. The auger was used for boring softer materials. It removed large quantity of material due to its wide size capacity, so had to be taken out to remove the cut material. Middle age Augers with spiral or helical flutes helped the evacuation of the cut material to the surface. Augurs are now used for pile foundation boring work, tree planting etc.

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Chinese, 2,250 years ago, used Augur based drilling device to drill shallow wells to tap brine aquifers for salt production. The rig was constructed from bamboos. The pile pipe with drill bit was allowed to drop by about one mt pulverizing the rock. By the beginning of the 3rd C. AD. wells were drilled up to 140 mts depth. In 1835 the Shanghai well was the first in the world to exceed a depth of 1000 mts in comparison, the deepest wells in the USA were about 500 mts deep.

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The other hand boring tools include the brace, a crank shaped device that can be held by one hand and rotated by another (action similar to car lifting jack), the push drill has a spiral flute along which a trunk moves down creating rotations but bounces back, on release of the compressed spring.

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The rotary hammer drill (masonry drill) combines a primary dedicated hammer mechanism with a separate rotation mechanism, and is used for more substantial material such as masonry or concrete.

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Table or platform drills are used in workshops for cutting holes in wood, metal, rock, or other hard materials. Table mounting is required where jobs are heavy, repetitive and precise. Platform mounting is used for simultaneous or multi drill operations. Tools for drilling holes in wood are commonly known as bits. A number of special forms of bits are also employed, including the expanding bit, which has a central guide screw and a radial cutting arm that can be adjusted to widen already drilled holes. For drilling metal, twist drills rotated by motor-drives are employed.

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Chucks are holding devices to drills of various sizes. Rock drills are hammered by pneumatic devices for creating holes to place explosive charges in mining and quarrying. A rotary drill consists of a single auger-like bit, or three inclined positioned circular sets of multiple bits moved by a toothed gear, and the gear rotated by a series of connected steel pipes. Rotary drills are used in drilling oil wells.

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Drilling and Boring Machines: Motorized drill machines not only drill new holes, and alter the existing holes by boring or reaming to enlarge it, cut screw threads by tapping it, or lap or hone a hole for accurate sizing (tolerances) and to provide a smooth finish. Drilling machines vary in size and function, ranging from portable to very large radial drilling machines, multi-spindle units, automats or automatic production machines, and deep-hole-drilling machines.

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Routers are machines with drilling spindles that move sideways to cut shallow to deep grooves with square or rounded sections to create engraved patterns in materials like wood, plastics and metals. Drilling machines are also operated with pressurized gas -pneumatically, to achieve very high speeds.

Common drills have a single cutting tip of steel made of hardened, carbon steel or tipped with cemented carbide or diamond. A carpenter’s hand held wooden drill takes forward and backward motion from the thong or bow-thread. The dual movement helps in drilling as well as evacuation of dust. Dual movement require double edged drilling bit, compared to a single direction movement bit, which are easy to make and re-sharpen. Drilling bits with spirally fluted columns came into practice much later, in 19th C.

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Drilling is done with a small diameter-axial movement so requires high speed and low torque. Drilling removes very little material per rotation. Boring is done with a large diameter so requires low speed but high torque. For finishing large bores grinding wheels are used. Grinding-wheel cutters have a planetary motion, rotating rapidly on their own axes, which in turn rotates on the internal face of the bore.

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