Why use Impact Wrench with Limited Torque in Your Shop?

Impact wrenches with limited torque ensure secure tightening and prevent accidents. Understand this solution.

In the automotive sector, automakers have strict quality control of manufacturing processes, in order to apply torques according to engineering specifications. Once the vehicle is out on the road, repair and maintenance routines in workshops and tire stores do not always guarantee that these specifications are met. In many cases, the torque applied is defined by the machine stopping moment — in turn determined by the operator. No matter how competent and knowledgeable the professional may be, the quality of the grip will always be questionable: after all, achieving the necessary touch is humanly impossible without the proper technology. In this context, accidents can occur either by a touch inferior to the specified one or by overtorque. The most serious cases — little reported by the media — happen when the wheel is detached from the moving vehicle. Therefore, let's understand the effects of overtorque and find out how it is possible to perform this tightening safely.

The effects of overtorque

When the torque is greater than necessary, excess voltage can cause three types of failures:

The screw hits the plastic zone: Every screw acts like a spring. When turning the screw head (torque), a tension is generated in its rotation axis. This tension produces the binding force of the desired parts. Thus, when the bolt receives a torque greater than that determined in the specifications (overtorque), there may be excessive deformation. The screw material plastically deforms, that is, it no longer returns to its initial position. No longer acting as a spring, the bond strength between the parts is reduced. In vehicles, the consequences of this phenomenon can be serious, with a high risk of loosening of the wheels in motion.

Screw breaks: With overtorque, the excessive stress generated can push the screw material to the limit, leaving it fragile enough to break with vibrations along the way.

The driver cannot change the wheel with a manual wrench : The indicated torque wrench for a car wheel varies between 95 to 130 Nm, depending on the manufacturer. If the value applied is much higher than the specified torque, it can occur from the breakage of the screw to the impossibility of loosening the wheels with a traditional wheel wrench, in case of a tire puncture.

How to avoid these problems?

The solution to ensure vehicle safety after any type of tightening is to use impact wrenches with limited torque. These tools limit the maximum amount of torque to be applied, eliminating the possibility of process failure.

Typically, these tools operate with a torque force slightly below that specified by the assemblers so that the tightening is completed with a torquemeter, ensuring even more precision.

Within the Chicago Pneumatic portfolio, there are touch-limited impact wrenches to meet different needs — light and heavy vehicles.

Light vehicle solutions

The CP7748 TL impact wrenches is considered the most powerful on the market in its category, reaching 1250 Nm of maximum real torque in reverse mode. In tightening mode, with 1 second of tightening, a maximum torque of 96 Nm is reached. For operations that demand mobility and a cleaner environment, without scattered cables, there is the CP8849 TL model , unique on the market – it is the first wrench for Battery impact with automatic stop. It has 2 tightening positions - 50% and 100% of the maximum tool torque, respectively.

Solutions for heavy vehicles

For this need, the recommended model is the CP7782 TL, the only impact wrench on the market with torque limitation to 500 Nm, tightening 1sec. It was specially developed to prevent overtightening in heavy vehicle bolts.

If a tightening was performed with overtorque in your company, the customer may never find out. But in such a competitive scenario, it is important that the workshops themselves educate customers so that they know how to value differentiated work.

In addition to ensuring customer safety, Chicago machines provide more savings due to greater durability and reduced maintenance cost over the tool life.