Portable Electric Drills
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Revision as of 14:59, 26 October 2015 by DT Online
The Power Drill is the most popular and versatile of all power tools and most home toolkits will have at least one. With suitable attachments* they are capable of much more than simply drilling holes. Most modern drills have a Keyless Chuck with a capacity up to 10mm or 13mm.
Originally designed as a Pistol Grip mains electricity powered (or corded) device, but battery powered (or cordless) versions are becoming more common. They are more convenient and the tendency now is to use the same battery pack on different single-purpose machines rather than use power drill attachments. 18 Volt drills are the most common and, in general, the higher the voltage, the more powerful and useful the drill.
*Note: When using power tools in schools, battery powered, single purpose tools are preferred and the use of attachments avoided [Ref: BS 4163 2007].
Many Portable Electric Drills have some form of speed control (e.g. either a two-speed gearbox or an electronic variable speed control) and some have Torque Control and Clutch with reverse, which can be helpful when driving in woodscrews for example. Drills used for making holes in masonry often include a Hammer Action.
Safety Point! The drill Clutch is designed to slip if too much Torque is applied. This can help prevent screws breaking off but is most important when drilling large diameter holes in masonry (e.g. with a Core Drill) to prevent personal injury caused by the drill being twisted out of the user's hand.
Most power drills have chucks which accept Parallel Shank drill bits (also triangular and hexagonal) but some purpose-made and heavier duty Rotary Hammer Drills have a chuck which is designed to have SDS Shank bits simply slotted in.
SDS Drills are commonly able to rotate as normal, rotate with hammer action, or apply hammer action without rotating. For this reason, a range of chisels and bolsters are available as SDS tools, in addition to masonry drills.
Cordless power drills with speed and Torque Control can be very effective also as powered screwdrivers but, more conveniently, a separate powered screwdriver can speed up working by avoiding the need constantly to change bits when drilling a series holes to receive screws. Such Drill Drivers are excellent when a constant Torque for precision work is required.
The effectiveness of Powered Screwdrivers is enhanced if a hammer-type action is applied as the screw is turned. This is the case with an Impact Screwdriver but note that the hammer-action acts in the direction of rotation to increase torque and not along the axis of the chuck as is the case with a Hammer Drill. Impact Screwdrivers are popular with Joiners working on construction sites with long, modern wax-coated and self-countersinking screws which cut their own way through softwood building timbers avoiding the need for clearance or pilot holes. Instead of a keyless chuck, Impact Drivers have a collet which accepts drill bits with hexagonal shanks.