Notcher Belt Sander Wet or Dry Grinder The belt sander uses an endless abrasive belt driven by an  electric motor to sand down metal parts much like the disk  sander unit. The abrasive paper used on the belt comes in  different degrees of grit or coarseness. The belt sander is  available as a vertical or horizontal unit. The tension and  tracking of the abrasive belt can be adjusted so the belt runs  in the middle.  [Figure 4-30] The notcher is used to cut out metal parts, with some  machines capable of shearing, squaring, and trimming  metal.  [Figure 4-31]  The notcher consists of a top and  bottom die and most often cuts at a 90° angle, although some  machines can cut metal into angles up to 180°. Notchers  are available in manual and pneumatic models able to cut  various thicknesses of mild steel and aluminum. This is an  excellent tool for quickly removing corners from sheet metal  parts.  [Figure 4-32] Grinding machines come in a variety of types and sizes,  depending upon the class of work for which they are to be  used. Dry and/or wet grinders are found in airframe repair shops. Grinders can be bench or pedestal mounted. A dry  grinder usually has a grinding wheel on each end of a shaft  that runs through an electric motor or a pulley operated by a  belt. The wet grinder has a pump to supply a flow of water  on a single grinding wheel. The water acts as a lubricant for  faster grinding while it continuously cools the edge of the  metal, reducing the heat produced by material being ground  against the wheel. It also washes away any bits of metal or  abrasive removed during the grinding operation. The water  returns to a tank and can be re-used. Grinders are used to sharpen knives, tools, and blades as  well as grinding steel, metal objects, drill bits, and tools.  Figure 4-33  illustrates a common type bench grinder  found in most airframe repair shops. It can be used to  Figure 4-32.  Power notcher.  Figure 4-30.  Belt sander. Figure 4-31.  Notcher. Figure 4-33.  Grinder. Tool rest 4-12