Bert spent 25 years working as a home-improvement and residential construction contractor in central Florida.
Anyone who attempts to drill into a cinder block with a twist bit from one of those cheap Chinese-made combo kits quickly realizes the importance of choosing the correct drill bit type for their particular project. The effects of using the wrong type of drill bit range anywhere from not cutting to burning up the bit's tip. Luckily most home projects require nothing more than one of the basic types of drill bits.
A drill bit consists of three main parts: the shank, point and body. The shank connects the bit to the drill's chuck. Two different shank styles fit most homeowner needs: round and 1/4-inch hex. Round shank drill bits work in drills with an adjustable chuck, while 1/4-inch hex shanks fit into impact drills with a 1/4-inch fixed chuck. The point initiates the hole and the body runs the length of the bit. Most bits use flutes that run the length of the body to channel debris out of the hole.
Twist Drill Bit
Many homeowners find the twist-style drill bit the most useful type of drill bit for use around the home because of its ability to work on a wide rage of materials, such as wood, plastic or metal. Choosing the right one becomes a bit more complicated when confronted with the many different styles and price ranges. Most projects simply need a general purpose or High-Speed-Steel drill bit, known as an HSS drill bit. Softer bits made from high-carbon steel perform okay on wood but dull quickly on metal and titanium covered bits last much longer, however they cost more. Some tasks, such as removing a broken bolt, do require a more expensive hard-metal twist bit. When using a hard-metal bit, maintain a low drill motor speed and keep the point lubricated with a light oil. This prevents the point from overheating.
A couple tips: To prevent drill bit wandering, dimple the metal with a center punch. Position the bit's point on the dimple and start the hole with the drill on low speed. When creating larger holes in thick metal, make a pilot hole with a small diameter drill bit and then work up to the desired size in stages.
Spade Drill Bit
Craftsmen commonly use a spade bit to quickly bore large holes in wood when the hole's appearance does not matter, such as during the construction phase of a major remodeling project. A spade bit, also known as a paddle bit, uses a pivot point to locate the hole exactly in its desired location. The spade bit's wide flat blade aggressively chews through wood. Unfortunately it often leaves a splintered exit hole. To improve the appearance of the exit hole, either clamp a sacrificial board to the back side or back the bit out once the pivot point breaks through and continue to cut the hole from the back side of the board.
Brad Point Drill Bit
Designed for use on woodworking projects needing an exact hole size and precise location, the brad-point drill bit looks like a cross between a spade and a twist bit. To prevent wandering, the tip's spade bit-like pivot point bites into the wood. The shape of the bit's cutting edge bores a clean hole, while the spurs located on the edge of the point reduce exit hole splintering. The body's flutes carry away debris when making the hole.
Carefully examining the points on a set of brad-point drill bits reveals two types of spurs: rounded and pointed. The rounded spurs work best with softwoods while the pointed spurs make excellent holes in hardwood. Rounded spurs slice through softwood grains without hanging up or tearing the wood fibers. A pointed spur sometimes snags softwood grains. However, the sharp pointed spurs make clean holes with minimal exit hole blowout when used on hardwoods.
Masonry Drill Bit
Contractors use a masonry bit to drill holes in cement, concrete, brick, masonry mortar, and some tile. Never attempt to use this type of bit on any kind of metal or the harder types of tile, such as porcelain or glass. A masonry bit's large triangle-shaped cutting point and thin shaft design make it easy to identify.
Craftsmen often pair a masonry bit with a hammer drill, especially when used on aggregate filled cement. A hammer drill pulsates the bit as it turns. This makes the bit act like a mini hammer. The rugged construction of the cutting point withstands a hammer-drill's pounding action. A masonry bit's thin shaft lessens friction during hole making. As the bit turns the shaft's flutes channel powdery debris out of the hole. Some commercial grade hammer drills employ an SDS-locking system. The SDS-locking system allows the bit to slide up and down as the drill rotates, creating a more forceful blow. Never use the hammer drill function when drilling through ceramic tile.
Tile Drill Bit
For some reason many DIY homeowners have difficulty choosing the correct drill bit for tile. It is amazing how many times I was called to replace a broken wall tile and install a shower door simply because the homeowner insisted on drilling the holes for a new shower door's anchors in wall tile with a regular twist bit. A regular twist bit easily penetrates the soft aluminum shower door frame, however, it simply scores the surface of the tile before either its tip overheats or the tile behind the frame cracks. A carbide-tipped masonry bit works well with most glazed ceramic tile. However, these bits tend to overheat when used on tile made out porcelain or glass. I have found that a Diablo-brand diamond-tipped drill bit easily cuts through any tile and the 1/4-inch size matches most shower door anchors. Some installers use a diamond-tipped hole saw to make larger holes, such as the hole for a shower arm. A spear tip drill bit also works with glass and other hard tiles.
To prevent the drill bit from wandering across the tile, place a piece of masking tape on the tile. Layout the holes on the tape with a pencil. Using variable-speed drill, start the hole on low speed and gradually increase the drill's speed to approximately medium as the bit digs into the tile; keep the drill on slow speed when using a spear tip on glass tile. The slower speeds keep the drill bit from overheating. Continue to apply moderate pressure until the bit pushes through the tile, then keep the drill running while pulling the bit from the hole.
This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.
© 2020 Bert Holopaw