Tool relted ergonomic factors affecting hand/arm safety.

1. Hand, Arm & Tool Safety
D. Rhodes, MSPH, CIH

2. Tool Grip
Body Grip Style Tools
• The grip is simply the
tool body.
• Diameter of grip may be
too large for best grip
• There is often no
protection from the
moving parts
• Poor at resisting high
torque forces on
hand/arm

3. Tool Grip
Body Grip Style Tools
• Some tool designs provide slender parts of tool bodies to grip or
a combination with attached in-line handle.
• A longer tool and spread out grips helps with resisting torque
• But, length puts the center of gravity father from the workers
body causing more torso strain and increases reaching

4. Tool Grip
Body Grip Style Tools
What are the safety advantages or disadvantages
of these pneumatic ratchets?
A B
C D

5. Tool Grip
Handle Size and Cross Sectional Shape
• Handle size affects grasping
force required
• High force increases muscle
fatigue and can contribute to:
– tendonitis
– carpal tunnel syndrome
– accidents from loss of or weak
grip
– blisters, calluses and hand
soreness

6. Tool Grip – Power Tools
Handle Size and Cross Sectional Shape
Tool handle length is important
for a comfortable safe grip.
• Select tools with handles a bit longer than
your bare hand – about 4.5 inches.
• When gloves are to be worn the handle
needs to be about 0.75 inches longer.
• For angled handles add an additional 0.75
inches to either of the above to a maximum
of about 6 inches.

7. Tool Grip –
Handle Size and Cross Sectional Shape
Handle girth is also important;
• For round handles, a
diameter of about 1.5 inches
causes the fewest problems
• For handles that are not
round, the perimeter
measurement should be
about 4.75 inches.
When gloves are to be used
both these measurements
should be slightly smaller.

8. Tool Handles –
Surface and Texture
A basic rule for handle
design is that they NOT
be fluted as in this
example.
The flutes rarely fit
individual users.
When they don’t fit, the
high spots create
pressure points that can
injure hands.

9. Tool Handles –
Surface and Texture
Other guidelines require a tradeoff because they are
contradictory.
When selecting tools, the work conditions need to be
considered and the best tool for MOST conditions
should be chosen.
– A knurled or rough surface helps reduce gripping force
especially when using gloves.
– BUT, deeply grooved or rough surfaces can collect
grime, chemicals, chips and particles which can irritate or
injure skin.
– A rubbery or soft handle can increase comfort of grasp and
improve grip but can absorb chemicals or trap sharp particles.