Measuring Torque Output for Electric Screwdrivers

An electric torque screwdriver is a precision torque control instrument and should be handled with care at all times. There are different methods for testing the torque output of an electric screwdriver. Each method has a key purpose. The video below provides a brief overview of the different methods.

In a calibration lab, you want to set the torque and verify the repeatability of the tool. When setting the torque value for an assembly power tool, you need a torque tester or torque sensor along with  a run down adapter. Make sure the torque capacity of the testing equipment fits within the torque range of the electric screwdriver.

When using a torque tester, place a run down adapter in-line between the drive of the tool and the transducer. Perform run downs and adjust the torque setting as needed for the electric driver. This serves as a simulated method.

The electric torque screwdriver typically features a scale on the torque adjustment nut, which lists a set of reference numbers. These numbers determine the approximate torque setting. Review the torque reference charts listed in the operation manual.

When the power tool is placed into the assembly station, you should verify the actual torque output on the actual fastening application. Use a rotary torque sensor to audit the power tool’s performance on the assembly application. Make sure the torque capacity of the testing equipment fits within the torque range of the electric screwdriver.

Connect the rotary sensor between an electric torque screwdriver and the fastening application. Monitor the torque being applied from the power tool to a fastener. There are items within the joint application that can impact the actual torque, like a soft rubber gasket or a plastic component.

Overtime, assembly tools start to drift out of tolerance. The best practice for monitoring this is to implement a torque testing system to be used as a tool checker. Routinely verify and audit the torque output of the electric screwdriver. Simple torque tests can be performed daily, weekly or monthly.

Torque Verifications & Audit Options

• A torque analyzer is placed in the assembly area and serves as a production line checker.
• Have a quality auditor routinely visit each assembly station. Use a rotary torque sensor with a torque testing display and verify the torque output.
• Use a mobile testing system in the production area. The cart is equipped with all the necessary torque measuring equipment. It provides a convenient verification process to ensure assembly tools are within tolerance.

Measuring torque is a continuous process. Testing and auditing an electric screwdriver should be part of the assembly process. As part of the overall quality control process, manufactures should include a “Torque Auditing” program.

Using quality torque measuring equipment makes a safer world through accuracy and precision. Measuring torque is essential for companies to ensure their product’s quality, safety and reliability isn’t compromised. The failure of a three-cent fastener that isn’t properly tightened can lead to catastrophic or latent failures. Fasteners that are insufficiently fastened can vibrate loose and excessive torque can strip threaded fasteners.