A drill and an impact driver are rotary driving tools that are helpful to have around the home, shop, or garage. An impact driver is also sometimes called an impact drill; however, a drill and an impact drill (or driver) are two distinctly different tools. They share some similarities and are often confused. A drill and an impact driver are different enough that it's worth having each tool on hand to cover a wide spectrum of building and repair needs.
What a Drill Is
Available in corded or cordless options, a drill rotates a drill bit clockwise to bore holes in materials by cutting and removing waste materials. A drill applies constant torque. Equipped with a driver bit, a drill can turn screws, bolts, and other fasteners into materials. The drill can reverse to remove the fasteners.
Users supplement the rotary power by pushing onto the drill from the back. Also, when drills bog down, one common trick to coax them along is to deliver short bursts by quickly pressing the trigger several times. It's these supplementary actions that relate the drill to the impact driver and that sometimes lead owners of drills to explore purchasing an impact driver.
Greater utility than impact driver
Can both drill and drive
Low-cost bits and drivers
Poor at driving long fasteners
Difficult fasteners require pre-drilling
Hard on the hand, wrist, and arm
What an Impact Driver Is
Shaped like a drill, an impact driver is usually shorter and smaller. It has many of the same features as a drill, such as a handle, trigger, and a type of chuck called a hex collet.
The difference between an impact driver and a drill is that an impact driver delivers more effectively the sequential bursts of power users often try to get with drills, which are achieved with the spring-loaded concussive force mechanism inside the tool. It delivers those bursts automatically, without the user having to do anything.
An impact driver also drills at a constant speed as needed and draws upon the bursting action when the driver senses resistance in the work material.
Impact drivers have long been used in the garage for vehicles. Small, cordless, lightweight impact drivers are a newer tool for home improvement.
Driving fasteners with great torque is the forte of impact drivers, not drilling holes. While you can use an impact driver in a pinch to drill a hole, that's not what it's best used for.
Easy on wrist and arm because torque is applied by the tool
Reduces chance of stripped screws
Smaller than most drills
High power ratio when compared to its size
No variable speeds
Poor for drilling
Not for hard, brittle materials like masonry
Requires special, expensive bits
More expensive than a drill
When to Use a Drill
Use a drill for boring holes with drill bits, for driving small fasteners into soft wood, and for drilling into masonry.
Owning an impact driver means that you can switch to using that for all fasteners except for the smaller ones. Because an impact driver is so powerful, it tends to draw in short screws faster than you might expect. This can result in pulling in the screw deeper than you want.
One application where this is particularly important is when driving drywall screws into drywall. You need to have precise control to prevent the screw head from drawing below the paper level and into the gypsum core. A drill will give you that level of control; an impact driver will not.
Use an impact driver for drilling into any type of masonry such as concrete, brick, or manufactured veneer stone.
When to Use an Impact Driver
Use the impact driver when you want to drive most fasteners, except for very short ones.
An impact driver is especially good for uses like driving 3-inch screws into wood, a task that is difficult for a drill even with pre-drilling the hole. Impact drivers excel at driving fasteners into dense or knotty wood.
You'll also want to use an impact driver for machine bolts or lag bolts.
Should You Buy a Hammer Drill?
A specialty type of drill you may want to consider is the hammer drill. A hammer drill combines rotational bursts with front-to-back movement (the hammering action) to bore into difficult masonry that presents an obstacle for ordinary drills.
If an impact driver has less utility than a drill, then a hammer drill has less utility than either of those two tools—at least for most homeowners. Purchase a hammer drill only if you anticipate doing a lot of drilling into masonry. Otherwise, consider renting or buying one.
Combination tools that offer both standard rotational action, as well as hammer drilling action, are now available. These can be useful for ceramic tile and light concrete block applications.
There are even combination tools available that offer all three forms of action: standard rotational drilling, impact driving with frequent rotational pulsing forces, and hammer drilling that adds linear hammering action to rotational hammering. Professional and advanced DIYers, however, usually prefer to have separate tools dedicated to each type of action. Several manufacturers offer tool kits that feature both a hammer drill and an impact driver.
Should You Buy an Impact Wrench?
An impact wrench is often confused with an impact driver, but while it looks somewhat like an impact driver, it has a different use. Rather than being to drive screws through wood, an impact wrench is more often used to secure or loosen machine nuts or bolts. They are more expensive, more powerful tools, but they operate at a slower speed than an impact driver. In automotive applications, the tool of choice is generally an impact wrench rather than an impact driver.
The hammering action of the tool is somewhat different. An impact wrench is designed to provide a sudden burst of rotational force, while an impact driver produces many short bursts of hammering force, which is necessary for driving long screws through wood. Impact wrenches are very often powered by air compressors, though electric and battery-powered types are also available.
Buy an impact wrench if you do a considerable amount of automotive work. Buy an impact driver if your main work involves carpentry-oriented construction.
Brushed vs. Brushless Motors
Increasingly, portable power tool designs are more likely to use brushless motors than the older more classic brushed style. Both corded electrical power tools and cordless battery-powered tools can use either design, though cordless tools are more likely to benefit from the brushless design.
All types of drills, hammer drills, impact drivers, and impact wrenches work by converting electrical current into rotating mechanical motion that spins a motor and attached spindle and chuck, but there is a considerable difference in how brushed motors and brushless motors accomplish this.
How Brushed Motors Work
In the classic brushed motor that was once the standard for power tools, the motor's components are found in a shell that contains permanent magnets. Inside this ringed shell of magnets, a series of wire coils (armature) is attached around a drive shaft that produces the mechanical motion. At the end of the armature coils, there is a component known as a commutator. As electrical current passes through this armature, it becomes magnetic, which begins to rotate as it is either attracted or repelled by the opposite polarities of the permanent magnet. This alternating attraction and repulsion cause the drive shaft to turn.
To keep the armature and drive shaft continually spinning, there are two wire brushes that rub against the commutator at the end of the armature, one carrying a positive charge, the other a negative charge. The polarity in the brushes switches rapidly between positive and negative, which causes the commutator, armature, and driveshaft to continue to spin in reaction to the fixed polarities in the permanent magnets on the outer shell.
Over time, these brushes experience wear and tear, which means they may need to be replaced, if possible. Or, if replacement isn't possible (as is the case with bargain tools), the tool may need to be simply discarded and replaced.
This classic design has been used in electric motors since its invention in the 1830s. It is a time-tested design that is still commonly used and has the advantage of being very inexpensive. Many bargain consumer-level tools use this design.
How Brushless Motors Work
In a brushless motor, the motor design replaces the commutator and metal brushes with an electronic circuit known as an inverter. This circuited component is responsible for generating the continuously revolving magnetic field that keeps the armature and rotor spinning in relation to the fixed magnets in the outer shell. Therefore, there is no need for the commutator or brushes in this design.
Thus, brushless motors are somewhat more efficient in their use of electricity, since they do not produce the friction, and resultant heat, caused by brushes rubbing against the other parts. This can be especially important for battery-powered tools, where charge life is a critical factor. And because there are no brushes to wear out, tools with brushless motors tend to last longer and require little or no maintenance.
And because they have fewer parts, tools with brushless motors can be more compact in design and quieter in operation. Further, they do not produce sparks that can potentially ignite flammable fumes. Finally, because of the reduced friction, tools with brushless motors produce more torque than brushed motors.
The downside of tools with brushless motors? There is only one: Tools with brushless motors can be as much as twice as expensive as those with traditional brushed motors. But when you consider that brushless motors provide better service for a much longer time than brushed motors, you're well advised to buy tools with brushless motors whenever possible.