Over sixty product types are listed in this section, ranging from pliers to chipping hammers. Many occupational risk factors associated with upper extremity Cumulative Trauma Disorders (CTDs) are directly related to hand and power tool design. It is also estimated that hand tools are involved in approximately 9% of all disabling injuries (Ayoub, et al., 1975).

Nine Principles Of Hand and Power Tool Design

1. DIRECTION OF FORCE EXERTION.

   Forces should be applied perpendicular to the axis of the tool handle, rather than along the axis of the handle.

2. AVOID SHARP EDGES.

   The tool handle should be rounded to avoid compressive forces against the soft tissue of the hand

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3. THE HANDLE SHOULD BE THE RIGHT SIZE.

   The right size for a tool handle is dictated to a large degree by the task to be performed. There are some general guidelines that can be followed:

   1. A handle should be 4.5 to 5" long to extend beyond the palm.
      
   2. A cylindrical handle should be approximately 1.5 to 1.75" in diameter.
      
   3. Pivot handles (e.g., pliers) should not exceed a 2.5" span at the point of force exertion.
      
      

4. MINIMIZE FORCE REQUIREMENTS.

   There are several means available to minimize the force requirements associated with hand tool use:

   1. Use a tool balancer or fixture to support the tool.
      
   2. Use a power tool to replace a manual tool.
      
   3. Provide springs on pivot handle tools to eliminate force requirements when opening the jaws.
      
   4. Avoid single finger triggers.
      
   5. Provide properly-fitted gloves.
      
   6. Keep cutting edges sharp.

5. DESIGN FOR THE RESTING HAND.

   Handles of tools should be curved such that the concave surface formed by the fingers and the convex surface formed by the heel of the palm and thumb are accommodated.

6. PROVIDE LEFT-HANDED TOOLS.

   Don't forget that nearly 10 percent of the population is left handed.

7. BEND THE TOOL, NOT THE WRIST.

   In general, the tool that is selected should allow the hands and arms to adopt neutral postures. This will be a function of both the hand tool and work surface orientation.

8. MINIMIZE EXPOSURE TO VIBRATION.

   Select tools that have good vibration damping features, and try to avoid prolonged exposure to vibration.

9. MINIMIZE EXPOSURE TO COLD.

   Exhaust air from tools should be directed away from the worker's hands. Avoid (e.g.) bare metal handles in cold weather.