Sawing machines are primarily used to part material such as rough-cutting excess material away before machining or cutting curved patterns in sheetmetal. Sawing machines substitute mechanical or hydraulic powered motion for arm motion to achieve the speed necessary for production operations. The cutoff operation is usually one of the first requirements in any production process before any machining, welding, or forging is done. The saw blade has individual teeth that “track” through the workpiece, each tooth deepening the cut made by the preceding tooth in the direction of feed. The saw or work may be fed and by controlling the direction of feed, either straight or curved cuts can be made. The width of the cut (also known as “kerf”) is approximately equal to the thickness of the saw blade and because of this saw blades are made as thin as possible but with adequate tool strength and rigidity.

There are three common types of sawing machines, reciprocating or hack saw, band saw, and circular saw. These machines all perform the same operation but vary in capability, capacity, and application. Power hacksaws use a reciprocating stroke where on the cutting stroke the saw blade teeth are forced into the metal either by gravity or hydraulic pressure while on the return stroke the pressure is automatically removed to prolong saw blade life. Most of the machines come equipped with a chip tray and a cabinet base which contains the coolant reservoir and its circulating pump. Heavy duty power hacksaws come with automatic bar feeds where the stock is loaded on a carriage which automatically moves forward the necessary distance when the cutting is finished. Hydraulic pressure automatically operates the vise jaws, gauges the material, and raises and lowers the saw blade.

After being set up for cutting material to a specified length, the power hacksaw will operate automatically without need for an operator until all the material loaded on the carriage has been cut. Horizontal band saws are one of the most widely used sawing machines for cutoff operations. These band saws range from small manually operated machines to large, fully automatic production machines. Vertical band saws are also used but are primarily manually controlled machines used in tool rooms and shops for maintenance and low production work.

Band saws have several advantages over other kinds of cutoff machines. The saw blade cutting width or kerf is 1/16 in (0.16 cm) compared to 1/8 in (0.33 cm) for power hacksaws and abrasive disc circular saws, and 1/4 in (0.64 cm) for cold saws. This can represent a sizable savings especially when cutting large or expensive material. The thinner saw blades also require less power to cut through material making them more economical to operate. Because bandsaws have endless blades (band saw blades are welded together to create an endless loop) which cut continuously, the cutting rates are much higher.

Two of the most popular circular saws are the cold saw and the abrasive disc cutoff saw. Cold saws are low rpm circular saws for metal cutting. These saws range in size from hand-operated bench-top models with 8 in (20 cm) blades to fully automatic machines with blades of 3 in (7.6 cm) diameter and larger. Light duty manual or automatic machines are sometimes equipped with a swivel head which enables cuts to be made at different angles. These saws are mostly used for cutting structural shapes such as I-beams, angles, and channel sections because the circular blades can complete their cuts with less travel than straight blades. Heavy duty machines are available with bar feeds and can be used for cutting solid bars up to 10 in (25 cm). Material larger than this size would require excessively large blade diameters, which must be more than double the cutting capacity, which would become too costly along with the machine necessary to drive them. Different speed ranges are provided for cutting metals of different hardness and toughness, and built-in coolant systems help produce better finishes and prolong blade life.

Abrasive cutoff saws utilize an abrasive disc to separate material by using a grinding action. Abrasive cutoff saws are built for either manual operation or with power feeds, with either fixed or oscillating wheel heads. Oscillating wheel heads are used when cutting thick sections of tough materials such as titanium, nickel-based super-alloys, and other high alloy steels. Sizes range from small bench-top machines with 8 in (20 cm) wheels to bigger machines with 20 in (50 cm) or larger wheels. Abrasive cutoff saws are very useful for rapidly cutting small sizes of bar stock, tubing, and structural shapes and also for cutting tough or hardened materials that cannot be cut efficiently with other types of saws.

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Article Source: http://science.jrank.org/pages/4043/Machine-Tools-Sawing-machines.html