18-07-2013, 01:01 PM
Cordless Tools
Cordless Tools .docx (Size: 366.27 KB / Downloads: 20)
History
The lathe is the oldest power tool, being known to the ancient Egyptians (albeit in a hand-powered form). Early industrial revolution-era factories had batteries of power tools driven by belts from overhead shafts. The prime power source was a water wheel or (later) a steam engine. The introduction of the electric motor (and electric distribution networks) in the 1880s made possible the self-powered stationary and portable tools we know today.[4]
Energy sources
Currently an electric motor is the most popular choice to power stationary tools, though in the past they were powered by windmills, water wheels and steam. Some museums and hobbyists still maintain and operate stationary tools powered these older power sources. Portable electric tools may be either corded or battery-powered. Compressed air is the customary power source for nailers and paint sprayers. A few tools (called powder-actuated tools) are powered by explosive cartridges. Tools that run on gasoline or gasoline-oil mixes are made for outdoor use; typical examples include most chainsaws and string trimmers. Other tools like blowtorches will burn their fuel externally to generate heat. Compressed air is universally used where there is a possibility of fuel or vapor ignition - such as automotive workshops. Professional level electric tools differ from DIY or 'consumer' tools by being double insulated and not earthed - in fact they must not be earthed for safety reasons.
Safety
While power tools are extremely helpful, they also produce large amounts of noise and vibrations.[5] Using power tools without hearing protection over a long period of time can put a person at risk for hearing loss. The US National Institute for Occupational Safety and Health (NIOSH) has recommended that a person should not be exposed to noise at or above 85 dB, for the sake of hearing loss prevention.[6] Most power tools, including drills, circular saws, belt sanders, and chainsaws, operate at sound levels above the 85 dB limit, some even reaching over 100 dB.[5] NIOSH strongly recommends wearing hearing protection while using these kinds of power tools.[7]
Prior to the 1930s, power tools were often housed in cast metal housings. The cast metal housings were heavy, contributing to repetitive use injuries, as well as conductive - often shocking the user. As Henry Ford adapted to the manufacturing needs of World War II, he requested that A. H. Peterson, a tool manufacturer, create a lighter electric drill that was more portable for his assembly line workers.[8] At this point, the Hole-Shooter, a drill that weighed 5 lbs. was created by A. H. Peterson. The Peterson Company eventually went bankrupt after a devastating fire and recession, but the company was auctioned off to A. F. Siebert,[9] a former partner in the Peterson Company, in 1924 and became the Milwaukee Electric Tool Company.[10]
In the early 30's, companies started to experiment with housings of thermoset polymer plastics. In 1956, under the influence of Dr. Hans Erich Slany, Robert Bosch GmbH was one of the first companies to introduce a power tool housing made of glass filled nylon.
Operation
Older alligator shears were powered by a flywheel. These shears ran continuously, which posed a safety hazard. Now alligator shears are hydraulically actuated. When actuated, the piston arm extends and slowly closes the upper jaw of the alligator shear, which passes alongside the bed or lower jaw of the shear to perform the cut.
Uses
Alligator shears are used for cutting long-length metal stock or scrap, generally where accuracy is not an important consideration, and the size or shape of the material makes other cutting or shearing options impractical- often the only other cutting option is cutting with a torch. Alligator shears are often used in conjunction with large metal shredders in the metal recycling industry, to 'clean' or prepare scrap for shredding by removing unwanted fittings or other parts the shredder will not accept.
Safety
The safety requirements for other powered metalworking shears are contained in ANSI B11.4, but alligator shears are specifically excepted from that standard. Federal OSHA and various state OSHA programs have requirements for guarding alligator shears, and newly-manufactured alligator shears are provided with guards that adjust to the size of the stock or scrap being cut. The purpose of this guard, however, is to prevent pieces of metal from being ejected during cutting. Such a guard also prevents inadvertent exposure of the operator's hands, but does not conform to more stringent 'point of operation' guarding requirements.
Racing
Belt sanders were one of the first power tools used in the growing field of power tool drag racing wherein a pair of stock or modified[1] belt sanders are placed in parallel wooden channels and fitted with long extension cords. Each heat begins when a common switch or individual switches triggered by the racers energizes them, causing the sanders to race towards the end of the track spitting wood dust along the way. Stock sanders race down a 50 foot (15 m) track, while modified sanders race on a 75 foot (23 m) track. Sanders of all shapes and sizes can go very fast or very slow, depending on the power of the motor. For example, some can go as fast as 5mph.