Portable drills
PURPOSE AND TYPES
The portable drill is a hand-supported, power-driven machine tool that rotates twist drills, reamers, counterbores, and similar cutting tools. The portable drill may be electrically powered by means of an internal electric motor or may be pneumatically powered . Portable drills are rated by the maximum size hole that can be drilled in steel without overtaxing the motor or drill.
Therefore, a 1/4-inch-capacity drill is capable of drilling a 1/4-inch diameter hole or smaller in steel. Portable electric and pneumatic drills rated at 1/4 to 1/2-inch maximum capacities are usually equipped with geared drill chucks for mounting straight, round shank twist drills or other similar tools by using a chuck key . Heavier portable drills (Figure) having a 3/4- to 1 1/4-inch capacity use taper shank chucks to mount drills and other similar tools.
Portable drills have many different characteristics depending on how the job is to be done. They may be set for one speed or they maybe variable speed drills. A variable speed drill is an excellent tool for use as a power screwdriver.
Portable drills may be equipped with a reversing switch to allow a screwdriver attachment to reverse bolts and screws out of holes. Special 90° angle portable drills are available for drilling in confined spaces where a standard size drill will not have sufficient clearance. For corners and tight spots, a 360° angle portable pneumatic drill is available which can be swiveled to any desired angle and locked into position. Most portable drills have a lock button near the on-off switch which allows for continuous operation without holding the trigger. Side handles and rear spade handles can be attached to most drills to stabilize drilling and to allow for better control. Special devices. such as a vertical stand or feed screw , can be used on some of the portable drills to make a job easier or more proficient.
The size, type. and power capacity of portable drills selected depends on the job to be performed. Before attempting a drilling job, check the capabilities of the portable drill with the manufacturer’s instruction manual.
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