Finding the Best Pneumatic Impact Wrenches for You
Air Compressor
The first thing you must evaluate to decide on the correct impact wrench is the capacity of the air compressor. It is important to ensure that the compressor delivers enough power for the impact wrench to function properly.
The way to determine if the compressor has the appropriate power for the impact wrench that you want to buy is to first know the flow rate (measured in cfm or cubic feet per minute, or liters per minute) and the minimum pressure (measured in psi, bars, kg/cm 2 or kPa) of the air that the impact wrench needs to function.
Most pneumatic tools require 90 psi (6.2 bar or 620 kPa) pressure, and impact wrenches are no exception. Too high pressures cause excessive wear and failure of the tool after a certain time. Conversely, tools that operate with too low an air pressure are often lacking when operating at full power.
For its part, the flow is a significant factor, because the compressor must be able to supply the air at a higher speed than that consumed by the impact wrench. Otherwise, you will lose torque capacity in the tool. In other words, for good performance, the compressor must exceed the air pressure and flow requirements of the impact wrench.
Anvil Size
Many fall into the error of thinking that the larger the anvil size, the better the performance of the impact wrench will be, but this is not necessarily the case. For example, would you use a 1-inch wrench to always loosen 10mm screws? Sure not.
Therefore, you must consider the size of the nuts, bolts, and screws that you will typically use and accordingly search for impact sockets of that size, as well as the anvil sizes that are compatible with those sockets.
Commercially available pneumatic impact wrenches for light to moderate use have three main anvil sizes: 1/4 inches, ½ inches, and 3/8 inches. The most powerful heavy duty and very heavy duty (e.g. removing wheel lug nuts from tractors, combines or trucks) have anvil sizes of 1/2 inches, ¾ inches, and 1 inch.
Power Capacity
You must keep in mind that the maximum torque is greater than the working torque. So, it is vital to know the suggested torque value for the service that you have to perform and add an extra amount for the difference between the working torque and the maximum torque. Generally, the type of service required a response to three variables:
- Very heavy: automotive, naval, aeronautical, railway assembly plants, agricultural and construction equipment.
- Heavy: the assembly of large machinery.
- Normal: maintenance or repair work.