Technology and our changing world high Technology

METALS - CUTTING BAND SAWS
The metal - cutting band saw cuts continuously. Since it uses a thin blade it removes little material. Some types of band saws can also beused in either a horizontal or vertical position. The blades have from four to fourteen teeth pa^- inch. They should be selected so that at least two teeth are engaged at all times. Fine-tooth blades are used for cutting th in metal and light tubing. Coarser blades areused for larger diameter stock.
Here are some directions that should be followed when using this saw:

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  Be sure that the blade has enough tension to keep it from weaving and making a crooked cut.
  
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  The feed pressure should vary according to the size and kind of material being cut. A slow speed and a steady, feed pressure will cause blades to last longer. Heavy pressure will dull the blade. A light feed will cause theblade to slip over the work and wear theblade. Use a lightfeed о thin materials. Use a heavier feed on thicker ones. A sliding weight is used for the feeder control. Move the weight away from lhe motor and to increase the feed.
  
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  Check the fixed jaw to make sure that it is at right angles to the saw blade for cut-off work. Jaws can also be adjusted up to 45° for angle cutting. Opai the jaws so that toe material will just slip in. Then release toe catch and lower toe blade so it lines up with your length mark on toe stock. Tighten toe vise. Turn on toepower. Release toe catch, and slowly lower toe saw to toe work. After this point toe cutting will be automatic. On some machines toe power is automatically turned off after toe cut is complete. Power hacksaws with heavy blades (like hand-hacksaw blades) are also used.
  

Cold Chisels
The cold chisel is used for both shearing and cutting stock. The cutting edge of toe cold chisel should be ground to an angle of 60° to 70° with a slightly rounded cutting edge. The cutting can be done by placing toe stock over a soft metal or wooden surface to protect toe cutting edge of toe chisel. Hold a cold chisel at a slight angle. Tap it with a hammer to start toe cut. After you have traced toe area to be cut, strike toe cold chisel with firm, careful blows to cut through toe metal. The cold chisel can also be used for shearing metal in a vise, or for shearing rivet heads. Fix the metal in a vise with toe cutting line just above toe top of toe jaws. Hold toe cold chisel at an angle of about30° or 35°. Strike it with a hammer to shear off toe metal.