Every now and then, we still come across someone who doesn't quite understand how an impact driver works. An impact driver is an essential tool for any professional. They allow you to apply more force (or torque) than the drill bit. When used in tandem, the cordless drill handles the holemaking, while the impact driver sets or sinks the fastener. For basic screwdrivers, an impact driver may be the only tool you need. If you've ever wondered how an impact driver works, this article should help answer your question.
How Impact Drivers Work Inside
First, if you want to know the difference between these two tools, check out our impact driver vs drill article. We don't want to repeat that here. Instead, we wanted to take a look at how an impact driver works internally to generate its impressive torque.
Constant pressure and shock
Common drill bits apply a static rotational force to the shaft, which in turn applies a static rotational force to the drill bit. In other words, it applies constant pressure to rotate the chuck. As the job gets harder, inertia kicks in. This drill fights against the user and wants to put as much force on your hands and arms as you put on the drill. If the bot binds, but the tool continues to provide all of its functionality, you could have some serious problems!
Impact drivers depend on something else entirely – which makes them a truly unique tool. An impact driver delivers a rotary impact when you need extra torque. It does this using a spring, hammer, and anvil.
When the motor turns the shaft, the spring compresses and then releases. This drives the hammer down forcefully until it drops to a position where it can rotationally strike the anvil. This action happened very quickly. In fact, most impact drivers deliver more than 50 impacts per second. This creates a force much greater than what a drill can typically muster in a similarly sized tool.
Push vs Quick Punch
Here's another way to think about it: using a drill is like putting your hand on an object and pushing. Using an impact driver is like making a quick hole. Think of it like the quick punches of the legendary martial king Ip Man… except less messy. You use the same muscles to generate both forces, but the overall power provided by the quick punch is much greater. The punch also only hits the surface for a short amount of time, while you can push for a longer period of time.
When and Where Impact Drivers Really Work
Like a punch, the impact mechanism creates a more violent action. That's why you'll see many pros shy away from impact drivers with twist and spade bits. While it gets the job done, the experience isn't as smooth.
On the other hand, this kind of violence is very effective for tightening screws. Impact drivers also tend to drive higher torque fasteners faster than drills. The speed of hammer/anvil impact combined with the added force allows you to drive longer and larger diameter screws or fasteners than you expect a drill to handle.
How Impact Drivers Provide More Torque
What an impact driver mechanism actually means comes down to how it delivers torque. Have long or larger ledger screws or lag bolts? An impact driver is the best tool for this type of work.
You can drive longer and larger bolts with standard drill bits. However, as you get closer to the bottom, torque requirements increase, forcing you to use the tool like hell for control. Compare that to using an impact driver to drive a ledger or lag screw all the way to the bottom with only one hand!
Smaller size impact driver
The icing on the cake is that impact drivers are typically smaller, lighter, and able to get into tighter spaces. The best impact drivers are less than 5 inches long! They also don't twist as violently as high-torque bits. If this all sounds impactful, you're not alone. Impact drivers are one of the most popular cordless tools on the job site.
Knowing how an impact driver works will also help you know when and where to choose it over a drill. These are tidbits of knowledge to help you transition from apprentice to seasoned professional.