There are many types of drills: some are powered manually, others use electricity (electric drill) or compressed air (
pneumatic drill) as the motive power, and a minority are driven by an
internal combustion engine (for example, earth drilling augers). Drills with a percussive action (
hammer drills) are mostly used in hard materials such as
masonry (brick, concrete and stone) or
rock.
Drilling rigs are used to bore holes in the earth to obtain water or oil. Oil wells,
water wells, or holes for
geothermal heating are created with large drilling rigs. Some types of hand-held drills are also used to drive
screws and other
fasteners. Some small appliances that have no motor of their own may be drill-powered, such as small pumps, grinders, etc.
Primitive Some forms of drills have been used since Pre-History, both to make holes in hard objects or as
fire drills. •
Awl – The shaft is twisted with one hand •
Hand drill – The shaft is spun by rubbing motion of the hands •
Bow drill – The shaft is spun by cord of a bow that is moved back and forth. •
Pump drill – The shaft is spun by pushing down on a hand bar and by a flywheel
Hand-powered Hand-powered metal drills have been in use for centuries. They include: •
Auger, a straight shaft with a wood-cutting blade at the bottom and a T-shaped handle •
Brace, a modified auger powered by means of a
crankshaft •
Gimlet, a small tool for drilling holes •
Bradawl, similar to a
screwdriver but with a drilling point •
Cranial drill, an instrument used throughout skull surgery • or hand drill, also known as an , as it is analogous in form to a hand-cranked
eggbeater with
bevel gears • Breast drill, a heavy duty subtype of eggbeater drill that has a flat chest piece in addition to one or more handles •
Push, such as
Yankee or Persian drills, which use spiral or
ratcheting mechanisms •
Pin chuck, a small hand-held jeweler's drill File:La_Tour.jpg|Painting by
Georges de La Tour of
St. Joseph operating an auger File:PalmercarpenterA.jpg|Carpenter using a hand-powered
brace to drill a hole File:drill004cropped.jpg|A traditional wheel brace or hand drill, with hollow wooden handle and screw-on cap used for storing bits
Power drills Drills powered by electricity (or more rarely, compressed air) are the most common tools in woodworking and machining shops. Electric drills can be
corded (fed from an
electric outlet through a
power cable) or
cordless (fed by
rechargeable electric batteries). The latter have removable battery packs that can be swapped to allow uninterrupted drilling while recharging. A popular use of hand-held power drills is to set screws into wood, through the use of
screwdriver bits. Drills optimized for this purpose have a
clutch to avoid damaging the slots on the screw head. •
Pistol-grip drill – the most common hand-held power drill type. •
Right-angle drill – used to drill or drive screws in tight spaces. •
Hammer drill – combines rotary motion with a hammer action for drilling
masonry. The hammer action may be engaged or disengaged as required. •
Drill press – larger power drill with a rigid holding frame, standalone mounted on a bench •
Rotary hammer combines a primary dedicated hammer mechanism with a separate rotation mechanism, and is used for more substantial material such as masonry or concrete. Most electric hammer drills are rated (input power) at between 600 and 1100 watts. The efficiency is usually 50–60% i.e. 1000 watts of input is converted into 500–600 watts of output (rotation of the drill and hammering action). For much of the 20th century, attachments could commonly be purchased to convert corded electric hand drills into a range of other power tools, such as orbital sanders and power saws, more cheaply than purchasing dedicated versions of those tools. As the prices of power tools and suitable electric motors have fallen such attachments have become much less common. Early cordless drills used interchangeable 7.2
V battery packs. Over the years battery voltages have increased, with 18 V drills being most common, but higher voltages are available, such as 24 V, 28 V, and 36 V. This allows these tools to produce as much
torque as some corded drills. Common battery types of are
nickel-cadmium (NiCd) batteries and
lithium-ion batteries, with each holding about half the
market share. NiCd batteries have been around longer, so they are less expensive (their main advantage), but have more disadvantages compared to lithium-ion batteries. NiCd disadvantages are limited life, self-discharging, environment problems upon disposal, and eventually internally
short circuiting due to
dendrite growth. Lithium-ion batteries are becoming more common because of their short charging time, longer life, absence of
memory effect, and low weight. Instead of charging a tool for an hour to get 20 minutes of use, 20 minutes of charge can run the tool for an hour in average. Lithium-ion batteries also hold a charge for a significantly longer time than nickel-cadmium batteries, about two years if not used, vs. 1 to 4 months for a nickel-cadmium battery.
Impact drills Also known as impact wrenches, is a form of drill that incorporates a hammer motion along with the rotating motion of a conventional drill. The hammering aspect of the impact drill occurs when the power of the motor cannot turn the bolt it will begin exerting bursts of force to "hammer" the bolt in the desired direction. These drills are commonly used to secure long bolts or screws into wood, metal, and concrete, as well as loosening seized or over-tightened bolts. Impact drills come in two major types, pneumatic and electric, and vary in size depending on application. Electric impact drills are most often found cordless and are widely used in construction, automobile repair, and fabrication. These electric drills are preferred over the pneumatic driven because of their maneuverability and ease of use. Pneumatic impact drills rely on air and have to remain connected to an air source to maintain power. The chuck on impact drills is different from the conventional handheld power drill. The chuck acts more as a collet with a hexagonal shape in which the bits and drivers lock into. Impact drivers can also be used to bore holes like a standard pistol grip drill, but this requires a special bit that will lock into the hexagonal collet. The design of the impact drills are almost identical to modern pistol grip power drills with only one major difference. Impact drills have a shorter, skinnier, stubby receiver where the collet is located compared to the larger tapered chuck on a conventional drill. This allows the user to fit in smaller places that a normal drill would not. Impact drills are not great in regards to torque and speed control. Most handheld drills have a variable speed option, whereas most impact drills have a fixed torque and speed. Impact drills are not designed for precision work due to this lack of adjustability.
Hammer drill --> The hammer action of a hammer drill is provided by two cam plates that make the chuck rapidly pulse forward and backward as the drill spins on its axis. This pulsing (hammering) action is measured in Blows Per Minute (BPM) with 10,000 or more BPMs being common. Because the combined mass of the chuck and bit is comparable to that of the body of the drill, the energy transfer is inefficient and can sometimes make it difficult for larger bits to penetrate harder materials such as poured concrete. A standard hammer drill accepts 6 mm (1/4 inch) and 13 mm (1/2 inch) drill bits. The operator experiences considerable vibration, and the cams are generally made from hardened steel to avoid them wearing out quickly. In practice, drills are restricted to standard masonry bits up to 13 mm (1/2 inch) in diameter. A typical application for a hammer drill is installing electrical boxes, conduit straps or shelves in concrete.
Rotary hammer The rotary hammer (also known as a rotary hammer drill, roto hammer drill or masonry drill). Standard chucks and parallel-shank carbide-tipped drills have been largely superseded by
SDS chucks and matching (spline shank) drills, that have been designed to better withstand and transmit the percussive forces. These bits are effective at pulverising the masonry and drill into this hard material. Some styles of this tool are intended for masonry drilling only and the hammer action cannot be disengaged. Other styles allow the drill to be used without the hammer action for normal drilling, or hammering to be used without rotation for chiselling. In contrast to the cam-type hammer drill, a rotary/pneumatic hammer drill accelerates only the bit. This is accomplished through a piston design, rather than a spinning cam. Rotary hammers have much less vibration and penetrate most building materials. They can also be used as "drill only" or as "hammer only" which extends their usefulness for tasks such as chipping brick or concrete. Hole drilling progress is greatly superior to cam-type hammer drills, and these drills are generally used for holes of 19 mm (3/4 inch) or greater in size. A typical application for a rotary hammer drill is boring large holes for lag bolts in foundations, or installing large lead anchors in concrete for handrails or benches.
Drill press A drill press (also known as a pedestal drill, pillar drill, or bench drill) is a style of drill that may be mounted on a stand or bolted to the floor or
workbench. Portable models are made, some including a magnetic base. Major components include a base, column (or pillar), adjustable table, spindle, chuck, and drill head, usually driven by an electric motor. The head typically has a set of three handles radiating from a central hub that are turned to move the spindle and chuck vertically. The distance from the center of the chuck to the closest edge of the column is the throat. The swing is simply twice the throat, and the swing is how drill presses are classified and sold. Thus, a tool with 4" throat has an 8" swing (it can drill a hole in the center of an 8" work piece), and is called an 8" drill press. A drill press has a number of advantages over a hand-held drill: • Less effort is required to apply the drill to the workpiece. The movement of the chuck and spindle is by a lever working on a
rack and pinion, which gives the operator considerable
mechanical advantage • The table allows a
vise or
clamp to be used to position and restrain the work, making the operation much more secure • The angle of the spindle is fixed relative to the table, allowing holes to be drilled accurately and consistently • Drill presses are almost always equipped with more powerful motors compared to hand-held drills. This enables larger drill bits to be used and also speeds up drilling with smaller bits. For most drill presses—especially those meant for woodworking or home use—speed change is achieved by manually moving a belt across a stepped
pulley arrangement. Some drill presses add a third stepped pulley to increase the number of available speeds. Modern drill presses can, however, use a variable-speed motor in conjunction with the stepped-pulley system. Medium-duty drill presses such as those used in machine shop (tool room) applications are equipped with a
continuously variable transmission. This mechanism is based on variable-diameter pulleys driving a wide, heavy-duty belt. This gives a wide speed range as well as the ability to change speed while the machine is running. Heavy-duty drill presses used for metalworking are usually of the gear-head type described below. Drill presses are often used for miscellaneous workshop tasks other than drilling holes. This includes sanding, honing, and polishing. These tasks can be performed by mounting sanding drums, honing wheels and various other rotating accessories in the chuck. This can be unsafe in some cases, as the chuck arbor, which may be retained in the spindle solely by the friction of a
taper fit, may dislodge during operation if the side loads are too high.
Geared head A geared head drill press transmits power from the motor to the spindle through
spur gearing inside the machine's head, eliminating a flexible drive belt. This assures a positive drive at all times and minimizes maintenance. Gear head drills are intended for metalworking applications where the drilling forces are higher and the desired speed (RPM) is lower than that used for woodworking. Levers attached to one side of the head are used to select different gear ratios to change the spindle speed, usually in conjunction with a two- or three-speed motor (this varies with the material). Most machines of this type are designed to be operated on
three-phase electric power and are generally of more rugged construction than equivalently sized belt-driven units. Virtually all examples have geared racks for adjusting the table and head position on the column. Geared head drill presses are commonly found in
tool rooms and other commercial environments where a heavy duty machine capable of production drilling and quick setup changes is required. In most cases, the spindle is machined to accept Morse taper tooling for greater flexibility. Larger geared head drill presses are frequently fitted with power feed on the quill mechanism, with an arrangement to disengage the feed when a certain drill depth has been achieved or in the event of excessive travel. Some gear-head drill presses have the ability to perform
tapping operations without the need for an external tapping attachment. This feature is commonplace on larger gear head drill presses. A clutch mechanism drives the tap into the part under power and then backs it out of the threaded hole once the proper depth is reached. Coolant systems are also common on these machines to prolong tool life under production conditions.
Radial arm A radial arm drill press is a large geared-head drill press in which the head can be moved along an arm that
radiates from the machine's column. As it is possible to swing the arm relative to the machine's base, a radial arm drill press is able to operate over a large area without having to reposition the workpiece. This feature saves considerable time because it is much faster to reposition the machine's head than it is to unclamp, move, and then re-clamp the workpiece to the table. The size of work that can be handled may be considerable, as the arm can swing out of the way of the table, allowing an
overhead crane or
derrick to place a bulky workpiece on the table or base. A vise may be used with a radial arm drill press, but more often the workpiece is secured directly to the table or base, or is held in a
fixture. Power spindle feed is nearly universal with these machines and coolant systems are common. Larger-size machines often have power feed motors for elevating or moving the arm. The biggest radial arm drill presses are able to drill holes as large as four inches or 100mm diameter in solid steel or cast iron. Radial arm drill presses are specified by the diameter of the column and the length of the arm. The length of the arm is usually the same as the maximum throat distance. The radial arm drill press pictured to the right has a 9-inch diameter and a 3-foot-long arm. The maximum throat distance of this machine would be approximately 36 inches, giving a maximum swing of 72 inches (6 feet or 1.8m).
Magnetic drill press A
magnetic drill is a portable machine for drilling holes in large and heavy workpieces which are difficult to move or bring to a stationary conventional drilling machine. It has a magnetic base and drills holes with the help of cutting tools like
annular cutters (broach cutters) or with
twist drill bits. There are various types depending on their operations and specializations, like magnetic drilling / tapping machines, cordless, pneumatic, compact horizontal, automatic feed, cross table base etc.
Mill Mill drills are a lighter alternative to a
milling machine. They combine a drill press (belt driven) with the X/Y coordinate abilities of the milling machine's table and a locking collet that ensures that the cutting tool will not fall from the spindle when lateral forces are experienced against the bit. Although they are light in construction, they have the advantages of being space-saving and versatile as well as inexpensive, being suitable for light machining that may otherwise not be affordable. ==Surgical==