The  following  paragraphs  are  devoted  to  the identification  general  operating  practices,  and  care  of these  tools. DRILLS The portable electric drill (fig. 1-62) is probably the most frequently used power tool in the Navy. Although it is especially designed for drilling holes, by adding various accessories you can adapt it for different  jobs.  Sanding,  sawing,  buffing,  polishing, screw driving, wire brushing, and paint mixing are examples  of  possible  uses. Portable  electric  drills  commonly  used  in  the  Navy have  capacities  for  drilling  holes  in  steel  from 1/16 inch up to 1 inch in diameter. The sizes of portable  electric  drills  are  classified  by  the  maximum size straight shank drill it will hold. That is, a l/4-inch electric drill will hold a straight shank drill bit up to and including 1/4 inch in diameter. The  revolutions  per  minute  (rpm)  and  power  the drill  will  deliver  are  most  important  when  choosing  a drill for a job. You will find that the speed of the drill motor decreases with an increase in size, primarily because the larger units are designed to turn larger cutting tools or to drill in heavy materials, and both  of  these  factors  require  slower  speed. If you are going to do heavy work, such as drilling in masonry or steel, then you would probably need to use a drill with a 3/8- or 1/2-inch capacity. If  most  of  your  drilling  will  be  forming  holes  in  wood Figure  1-62.-1/4-inch  portable  electric  drill. or small holes in sheet metal, then a l/4-inch drill will probably  be  adequate. The chuck is the clamping device into which the drill  bit  is  inserted.  Nearly  all  electric  drills  are equipped  with  a  three-jaw  chuck.  Some  drills  have  a hand-type  chuck  that  you  tighten  or  loosen  by  hand, but most of the drills used in the Navy have gear-type, three-jaw  chucks,  which  are  tightened  and  loosened  by a chuck key, shown in figure 1-63. Do not apply further pressure with pliers or wrenches after you hand tighten the chuck with the chuck key. Always remove the key IMMEDIATELY after you  use  it.  Otherwise  the  key  will  fly  loose  when  the drill motor is started and may cause serious injury to you or one of your shipmates. The chuck key is generally taped on the cord of the drill; but if it is not, make sure you put it in a safe place where it will not get  lost. All  portable  electric  drills  used  in  the  Navy  have controls similar to the ones shown on the l/4-inch drill  in  figure  1-62. This drill has a momentary contact trigger switch located in the handle. The switch  is  squeezed  to  start  the  electric  drill  and released to stop it. The trigger latch is a button in the bottom of the drill  handle.  It  is  pushed  in  while  the  switch  trigger is held down to lock the trigger switch in the ON position. The trigger latch is released by squeezing and  then  releasing  the  switch  trigger. DISK  SANDER Electric disk sanders (fig. 1-64) are especially useful on work where a large amount of material is to be removed quickly, such as in scaling surfaces in Figure  1-63.-Three-jaw  chuck  and  chuck  key. 1-37