An auxiliary arm (often referred to as a torque reaction arm or tool support arm) is a specialized, smaller-scale manipulator used to support hand-held power tools like nut runners, screwdrivers, and drills.

While the primary pneumatic manipulator arm handles the “bulk” lifting of heavy parts, the auxiliary arm is the “precision partner” that manages the forces generated during the final assembly stage.

The Primary Function: Torque Absorption
The most critical role of an auxiliary arm is to neutralize torque reaction. When a high-torque tool tightens a bolt, the tool tries to spin in the opposite direction.
Without an arm: The operator’s wrist and shoulder must absorb this force, leading to repetitive strain injuries or carpal tunnel syndrome.
With an arm: The rigid structure of the auxiliary arm absorbs 100% of the rotational force, transferring it into the workbench or floor mount instead of the worker.

How it Complements Manipulator Arms
In many industrial cells, you will see both a large pneumatic manipulator and a smaller auxiliary arm working in tandem:
The Manipulator Arm: Picks up a heavy engine block (150kg) and positions it on a jig.
The Auxiliary Arm: Holds the 5kg high-torque nut runner. The operator pulls the tool down, and the auxiliary arm ensures it stays perfectly aligned while absorbing the 80 Nm of torque required to secure the bolts.

Key Benefits for the Workstation
1. “Weightless” Tooling
Like their larger counterparts, auxiliary arms use gas springs or pneumatic cylinders to counterbalance the tool’s weight. A 10lb (4.5kg) tool feels like it weighs nothing, allowing the operator to guide it with one finger.

2. Precision and Alignment
Auxiliary arms often feature 90-degree adapters and locking pivots. This ensures that every screw or bolt is driven in perfectly straight, eliminating “cross-threading”—a major cause of product rework in automotive and electronics manufacturing.

3. Integrated Sensors (Smart Arms)
Modern “Smart” auxiliary arms are equipped with encoders. They can track the tool’s exact position in 3D space to ensure the operator:
Tightens bolts in the correct sequence
Doesn’t skip a bolt
Applies the correct torque for that specific location