Special Tools For Hard Spots
For drilling in masonry, you will need carbide-tipped bits designed for the work. The least expensive cost less than $3 and are fine if you drill only a few small holes once in a while. If you have more holes to drill, it's worth looking for industrial-quality bits. They are machined, not twisted, and use higher grades of steel and carbide, both of which extend bit life. Although they only cost about $1 more than low-end models, they will last a lot longer. They are now available at some home centers (The Home Depot carries such a line) and hardware stores. If you don't find them, check with an industrial-supply house, which you'll find in the yellow pages. For large jobs, step up from your rotary drill and use a percussion drill, sometimes called a hammer drill (tool-rental outlets usually carry them). These tools combine a turning motion with a high-frequency hammering action. Because they combine rotation and vibration, percussion drills are faster and more effective in concrete. And typically, these tools can be used in either a hammer mode or a standard rotary mode. Bits for percussion drills have a slight back-bevel on the carbide tip -- called a negative angle -- which helps prevent chipping. Many bits designed for percussion drills also may be used in rotary drills. For the really heavy stuff, there are rotary hammers, industrial-grade tools that turn more slowly than rotary or percussion drills and pound more forcefully on the end of the shank. These tools require special bits. When drilling in an unusually hard or abrasive material, like red brick and some types of stone, ask for bits with extra-hard carbide tips.
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