Heavy Duty Portable Drill

Tools and Machines

The portable electric drill consists of a housing with a handle, a motor, and a chuck.  Most of these electric drills have a key-type chuck.  These tools are made in a variety of shapes.  The most common shapes are the pistol-grip drill which usually will hold drill bits up to 1/4", and the spade handle drill which usually has a chuck capacity up to 1/2".

Safety for The Portable Electric Drill

  • Review general safety rules for use of portable electric tools.
  • Disconnect the power plug before installing or removing drills.
  • Make certain the drill is clamped securely in the chuck.
  • Be sure the key has been removed. 
  • Do not force the drill, always use an even steady pressure.
  • Never use a bit with a square tang or a lead screw.
  • When laying the drill down, always have the point away from you, even when it is "coasting" to a stop.
  • Never drill through cloth
  • Always clamp small pieces; do not hold them with your fingers when drilling.

Some drill housings are made of plastic in order to reduce the danger from shock.  Others have a built-in variable speed unit, with the speed varying directly with the amount of pressure exerted on the trigger switch.  The cutting tools can be twist drills, auger bits (if they have straight shanks), or spade (speed) bits.

The combination drill and countersink is a convenient tool for inserting wood-screws.  It is always necessary to drill the correct size holes for wood-screws to prevent splitting the workpiece and to get the maximum holding power.  This is usually a three-step procedure, if the screw is to be countersunk.  The combination drill, however, will drill the pilot hole, shank hole, and the countersink, all in one operation.

Drilling Holes

When drilling holes with your portable electric drill always use the correct bit or accessory. Make sure the tool (preferably of high-speed steel) is sharp. Apply just enough pressure to the drill to keep it cutting.  Too little pressure will make the drill dull;  too much pressure may cause it to stall or break. To prevent break-through splintering, clamp a piece being drilled. Always clamp the wood in a vise, or hold it securely with a clamp.  Hold the tool at right angles to the work when drilling a straight hole. This can be checked by using a try square to align the tool.  If the drill is equipped with a variable speed unit, it can be used as a powerful screwdriver by inserting a screwdriver bit. Start the screw slowly, increase the speed as the screw moves into the stock, and finish by slowing to a stop. On a standard-speed drill, a speed reduction ratchet attachment must be used for installing screws.