How much torque does an impact driver need? More is always better, right?
In today's power tool world, pushing the limits of more power isn't just a 1990s Tim Allen sitcom. When you see two impact drivers for the same price and one has more power than the other, you want more power, right?
Advantages of High Torque Impact Drivers
- High-torque impact drivers can replace the need for lightweight impact wrenches
- Fully capable of general screw driving at lower speeds
Disadvantages of High Torque Impact Drivers
- Requires an adapter that breaks easily on hard metal fasteners
In general, impact drivers with 1500-1800 inch-pounds of torque are more focused on higher rpm. It does 95% of the work faster than more torquey, slower tools.
Our experience is that if you need to use a socket adapter, you're better off grabbing an impact wrench.
The role of the impact driver
Most manufacturers expect their impact drivers to be able to drive screws. Self-tapping screws, deck screws, and structural screws (horizontal wood screws, or wood screws) make up the largest category of fasteners we use. Anything significantly larger than that will force us to switch from screwdrivers and nut drivers to sockets.
The most powerful impact driver in our best impact driver review article crushes 2,656 inch-pounds of tightening force and 4,200 inch-pounds of break-off torque. After a quick conversion to ft-lbs, these numbers are 221 and 350 ft-lbs, respectively.
In other words, they came out with a lightweight impact wrench number. With this kind of power, you can skip the 3/8-inch impact wrench. Just leave 1/2 inch of space for larger fasteners. There is no doubt that changing tools increases the value of your impact driver.
too much torque problem
But the growing number of broken 1/4" hex to 1/2" square drive adapters shows us the inherent problems of using an impact driver instead of an impact wrench. Especially when it comes to metal fasteners, you will quickly pass the adapter.
They may only be a few dollars each, but after a few dozen dollars, you'll be getting a new impact wrench paired with the batteries you already have.
We started breaking adapters on impact drivers that were spec'd 1700 in-lbs or larger. Higher torque impact drivers are definitely still available, though. Unless we were driving big screws into wood, we just dropped from full speed to one of the medium modes.
Generally speaking, a 1500-1800 in-lbs impact driver with more emphasis on higher RPM will do 95% of the work faster than an impact driver with more torque and slower speed.
Our rule of thumb: If you need to use a socket adapter, you better get an impact wrench!