Evaluation of handle design characteristics in a maximum screwdriving torque task

Area of Science:

• Ergonomics and Human Factors
• Biomechanics
• Product Design

Background:

• Understanding how tool design impacts user performance is crucial for developing effective and safe tools.
• Screwdriver handle characteristics, including shape and surface material, are known to influence grip and force application.

Purpose of the Study:

• To investigate the influence of screwdriver handle longitudinal shape, lateral shape, and surface material on torque performance, finger force distribution, and muscle activity.
• To determine optimal screwdriver handle designs for maximizing torque output in maximum screwdriving tasks.

Main Methods:

• Twelve male subjects performed maximum screw-tightening exertions with various screwdriver handles.
• Handles varied in longitudinal shape (circular, hexagonal, triangular), lateral shape (cylindrical, double frustum, cone, reversed double frustum), and surface material (rubber, plastic).
• Torque output, finger force distribution, and muscle activity were measured.

Main Results:

• Rubber handles yielded 15% more torque (5.73 Nm) than plastic handles (4.86 Nm).
• Vertical workpiece orientation produced higher torque (5.9 Nm) than horizontal (4.69 Nm).
• Circular or hexagonal cross-sectional shapes with double frustum and cone lateral shapes showed optimal torque performance and reduced finger force.

Conclusions:

• Screwdriver handle design significantly affects torque performance and user exertion.
• Optimal designs for maximum torque involve circular or hexagonal longitudinal shapes, specific lateral shapes (double frustum, cone), rubber surfaces, and vertical workpiece orientation.