Properly applied torque is vital to ensuring the safety of a vehicle and its passengers. Torque limiting tools are essential in helping tighten wheel nuts to the correct torque.
But what is a torque-adjustable impact driver, how does it work, and which tool is best? Here's more information to make sure you're not over-tightening tire lug nuts and endangering lives.
A torque-adjustable impact wrench provides efficient torque level control with limited torque in the forward direction to prevent overtightening. The tool does not stop working, but the torque increases more slowly, ensuring you do not overtighten the nut.
There are two types of torque adjustment technologies, both designed to reduce forward power once a certain torque is reached:
Let's take a closer look at both to understand which one provides the best performance:
When you polarize the hammer, the anvil, or both, the two components "slide" over each other, and even if they are still, the impact of the impact is less strong.
There are two types of airflow modifications, both designed to slow the rotor and therefore provide less power. A better example is a drawing of an air motor without torque regulation:
On a standard non-torque hammer drill without airflow modification, the diameter of the air intake port is the same in the forward and reverse directions. As a result, it generally provides the same torque levels in forward and reverse directions. You can see this in the picture below:
Air motor without torque adjustment (forward position)
a: air flow
b: input port
c: engine (including blades, rotor and cylinder)
d: exhaust port
Torque adjustable air motor with reduced inlet port
Air passes through a smaller inlet port, which reduces airflow and allows less air to enter the rotor, so the rotor spins slower. As a result, the power of the rotor-driven impact mechanism is lower. See the picture below:
Torque adjustable air motor with reduced air intake port (forward position)
a: air flow
c: engine (including blades, rotor and cylinder)
d: exhaust port
e: reduced input port (smaller compared to tool without torque limitation)
Torque adjustable air motor with threshold exhaust port
In this case, the travel distance of the rotor from the start of rotation to the exhaust is shorter and therefore the rotor rotates slower. See the picture below:
Torque adjustable air motor with threshold exhaust port (forward position)
a: air flow
b: input port
c: bladed rotor motor
f: threshold exhaust port
Mechanically modified torque-limited impact wrenches are naturally exposed to vibration because they work dependent on a hammer and anvil in physical contact. They also experience more friction at the point of contact, which creates heat and acts as a potential source of failure. Here, choosing tools that make airflow modifications can be a great advantage. Tools with less inlet air flow consume less air and benefit significantly from less vibration compared to tools with mechanical modifications. Depending on the brand and manufacturer, tools with airflow modification may also reduce forward vibration compared to tools with a non-torque adjustable design. This helps protect workers from Hand-Arm Vibration Syndrome (HAVS), a common but disabling musculoskeletal disorder caused by intense and repeated exposure to vibration, which is often permanent but easily preventable. No matter what technology the tool uses, both mechanical modifications and airflow modifications ensure that the optimum torque level is not exceeded once it is reached. This helps avoid the risks associated with overtightening.
REMINDER - Air line installation
To get the most out of your pneumatic tools, make sure the air line is properly installed and maintained. Note that all manufacturer recommendations are based on 6.3 bar air inlet pressure. Read our guide to learn how optimizing overall equipment efficiency (OEE) can help you maintain productivity, ensure workplace safety and the best return on your investment.
Torque-controlled tools have a stop function that monitors forward torque to prevent overtightening. The tool stops working when the given torque is reached. In contrast, a torque adjustable impact wrench does NOT stop working, it just stops increasing the torque.