An impact driver is a power tool that provides high torque to loosen or drive-in screws that are jammed due to rust or over-torqued.
In this guide, you are going to learn all you need to know about impact drivers.
I will explain how impact driver works, the advantages and disadvantages over cordless drill/driver and buyers guide explaining what to look for while picking up a new impact driver.
When you think of iconic, must have power tools that you will find in every garage, what do you usually think of? Most people will probably say cordless drills, circular saws, etc., tools like that. What most people probably would not name, are impact drills/drivers. Although they are not a well-known tool, at least when compared with cordless drills and saws, they are a very useful tool to have around.
What is an Impact Driver and why should I get one?
Impact drivers are small, cordless drill like tools, that are used to loosen screws and nuts that are unable to be taken out by a traditional screwdriver. They are also used to tighten screws and nuts that need to be tightened with more torque than can be provided by a screwdriver.
Impact drivers are stubby with a shorter head. The major difference, when compared to a standard drill/driver, is that it has a special impact driving mechanism that kicks-in, when the force exerted by the motor is not enough. Another key difference is that the impact drivers have hexagonal-shaped collets instead of a traditional 3 jaw chuck.
You can also use the impact drill/driver for drilling holes. But you must get drill bits with hexagonal shanks which usually are not available in smaller increments in diameter.
This powerful tool was once considered a specialty tool, only used by serious contractors and professional carpenters. However, with the rising popularity of DIY (do it yourself) home repair, it has become more common to keep a cordless impact driver around the house.
Uses of Impact Drivers
They can be used on a wide array of jobs; everything from building decks to tightening some screws around the house can be made easier by having an impact driver. But there are some cases where impact driver performs exceptionally well.
- To drive-in self-threading screws.
- Loosen over-torqued and corroded screws, bolts and nuts.
- Driving long and thick fasteners into hard material
- Remove car break-drums.
Impact drivers are highly useful for construction workers, cabinet makers and jobs that require the use of a large number of fasteners.
How do Impact Drivers work?
Impact drivers essentially work by combining the rotational motion with a hammering action to generate high torque. If you have no idea what that means, picture it this way. Imagine while you are turning a screw, you started tapping it with a hammer in the direction of rotation. The screw would go in faster. That is essentially what an impact driver does.
When the motor alone is unable to provide torque to fasten or unfasten a screw, the spring-loaded hammering mechanism actuates. The hammer mechanism lifts-up and rotates around and then is pushed down by the spring. It then hammer hits the output shaft transferring the rotational torque to it and this is repeated. This concussive blows to the spindle results in very high torque to the spindle.
Here is a video that explains the working principle of an impact driver.
In the video, you can see that when the spring forces the hammer down it releases with an impact on to the output shaft. As a result, the energy stored in the spring is also transferred to the head along the linear axis.
An impact driver gives a blow to the screw around 50 times a second, which produces upwards of 5 times more torque than your average cordless drill. So, if you are having issues getting a screw through tough material, then you may want to try swapping out a cordless drill for an impact driver.
Note: Do not get confused impact driver with a hammer drill. In the latter, the hammering action is applied only at the rear end of the drill and not in the rotational direction. You can see more details in the impact driver vs hammer drill article.
Keep in mind that there is no option to change the torque on an impact driver. The only control you have is on speed which you can vary using the control trigger. This is the reason why impact drivers are primarily used for loosening nuts, bolts, and screws. If you want more accurate torque control, get a drill/driver or a combi drill.
Advantages of Impact Drivers compared to Cordless Drills
Impact drivers sound very similar in concept to cordless drills, so you may be asking “what is the point of using an impact driver when I can just use a cordless drill to do most of the same jobs?” Well, there are certain advantages and disadvantages when it comes to using an impact driver versus a cordless drill.
- Higher Torque: As discussed before, impact drivers are much more powerful (about 5 times as powerful) when compared to cordless drill/driver. So, when you need drive screws in tough material, you will be able to do them faster and better with an impact driver.
- Fits in tight spaces: Impact drivers are compact and easier to hold for long periods of time. If you have seen an impact driver before, then you know that the head-length is shorter than the average cordless drill. This means impact drivers can be used to squeeze into tight spaces that you might not be able to comfortably maneuver a cordless drill into.
- Self-driving Screws: This power tool is particularly convenient when you are using self-driving screws that don’t require you to drill a hole. Such operations demand higher torque than that of a regular drill/driver.
- Less recoil and less likely to strip screws: There is next to no kickback or recoil when using an impact driver. Anyone who has used a cordless drill can testify to how annoying kickback can be. There is nothing worse than drilling into something, only to lose control of the drill because of some unexpected resistance which the caused the drill to experience kickback. Because of their immense power, impact drivers pretty much never experience kickback.
- Easy on Your Wrist: Because they do not experience resistance, and because they are lighter, impact drivers do not wear out your wrist as fast as cordless drills. Try using an impact driver for a day, and then try using a cordless drill for a day; your wrist will feel much better after a day with an impact driver, trust me.
- They are not cheap. Despite their compact design, impact drivers may cost you a pretty penny, especially if you want extras like more batteries.
- You will need impact driver compatible bits. The impact drivers lack 3-jawed chucks. Basically, this means that your impact driver may not be able to hold most of your drill bits. Because they usually are fitted with ¼-inch hexagonal socket head. So you may want to purchase hexagonal shank bits that are meant to work specifically with impact drivers.
- Impact drivers lack torque control. Torque control is a feature on most cordless drills that lets you choose how much torque is going to be applied when you press the trigger on the drill. When used properly, it helps you stop your drill from damaging screws and the surface you are drilling into. Since they do not have torque control, you will have to be extra careful when using an impact driver; otherwise, you will have a lot of stripped screws and damaged surfaces on your hands.
Impact Driver Buyers Guide
If you are deciding to get an impact driver, either for yourself or as a present for someone else, but do not know where to start, do not worry, because I am here to help. I have written this guide to inform people about what to look for when buying an impact driver
In this section, I am going to tell you the key features you should look for when shopping, the top brands and where to buy.
What to look for when buying an impact driver
Now that you have understood the advantages of impact drivers, let us find out how to get the best impact driver for you. Following are some of the key factors to look for when choosing an impact driver.
So obviously you will want a powerful impact driver. Power is measured by looking at the torque and voltage.
Torque is normally rated in Newton-meter (Nm) or inch-pounds (in-lbs). The torque usually ranges between 100Nm to 200Nm (approximately 1800 in-lbs). Consider what you need the tool to do. Do you need maximum power? Well, then look for an impact driver with lots of torque and a high voltage battery.
However, keep in mind that once the impact mechanism kicks-in you can’t control the amount of torque.
If you are going to be working on a lot of screws in quick succession, go for an impact tool with a high RPM count. While speed may not be very important criteria for driving screws, RPM is important for drilling. If you are planning to use your impact driver for drilling, get one that offers multiple- variable speeds.
Cordless impact drivers run on rechargeable batteries. So try and look for impact drivers that have batteries that hold a charge for a long time. Or impact driver kits that come with multiple batteries. There is nothing more frustrating than being in the middle of a job and having your battery die.
The drive source of the electric impact driver is the electric motor. If you can afford it, get an impact driver with a brushless motor. They are more energy-efficient, do not heat-up like regular motors and draw less battery power.
Size, weight, and comfort
When buying an impact driver carefully evaluate how it feels in your hand, how much it weighs, and how much space it takes up. One of the reasons people buy an impact driver is that it is easy on your wrists. You will likely be holding an impact driver for long periods of time, so make sure it is comfortable to use.
Best Impact Driver Brands
Most of the top power tool brands produce impact drivers. Their performances are very close. Some of the popular brands include,
If you are going for a cordless version, then I suggest you to stick with your existing power tool brand. That way, you can often interchange the batteries between the cordless tools.
Impact drivers are highly useful power tool that you may want to add in your arsenal. When you buy an impact driver, look for power rating, RPM, weight, size, and battery life.
I suggest you check our list of best impact drivers where you can find our recommendations.
If you are a hobbyist doing small woodworking projects you may not need a powerful tool. Use the regular drill/driver for drilling and driving screws in softwood, plastic, plywood, and other softer material. You need an impact driver for work that requires you to drive long thick screws into hard material and to unfasten tight bolts and screws.