Evaluation of handle shapes for screwdriving

Area of Science:

• Ergonomics
• Human Factors Engineering
• Biomechanics

Background:

• Screwdriving tasks are common in various industries.
• Handle design influences user comfort, force exertion, and task efficiency.
• Understanding the interplay between handle geometry and user biomechanics is crucial for tool design.

Purpose of the Study:

• To investigate the impact of screwdriver handle shape (longitudinal and lateral), surface material, and workpiece orientation on user discomfort and performance.
• To analyze finger and phalangeal forces during screwdriving to understand biomechanical contributions.
• To identify preferred handle designs that minimize discomfort and optimize force application.

Main Methods:

• Participants performed screwdriving tasks using handles with varied longitudinal (circular, hexagonal, triangular) and lateral (cylindrical, double frustum, cone) shapes, and surface materials (plastic, rubber-coated).
• Subjective discomfort, screw-tightening rotations, insertion time, axial force, and finger contact forces were measured.
• Phalangeal segment force distributions were analyzed to determine finger roles in force generation.

Main Results:

• Index and little fingers primarily guide and balance the screwdriver, while middle and ring fingers are key for gripping and turning.
• Preferred handle shapes included circular and hexagonal longitudinal, and double frustum and cone lateral designs.
• Handles with circular, cylindrical, and double frustum shapes, particularly the circular-longitudinal with double-frustum-lateral combination, resulted in the least total finger force and discomfort.

Conclusions:

• Screwdriver handle geometry is a critical factor in reducing physical strain and improving user experience.
• Optimized handle shapes, specifically circular-longitudinal with double-frustum-lateral, can enhance screwdriving task performance and user comfort.
• The findings provide valuable insights for designing ergonomic screwdrivers to prevent musculoskeletal discomfort.