Portable Electric Drills
From DT Online
Description
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].
Features and Applications
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.
*Note: The SDS bit was developed by Hilti and Bosch in 1975. The name comes from the German: "Stecken – Drehen – Sichern" (Insert – Twist – Secure) but Bosch marketing now uses "Special Direct System" for international purposes.
