1 ISE 311 Handtools Extend the capability of the hand Selection criteria:  What the tool can do  How the tool is used

2 ISE 311 Guidelines 1: Use Special-Purpose Tools __________________ 2: Design Tools to Be Used by Either Hand __________________ 3: Power with Motors More Than with Muscles __________________ 4: Use the Proper Grip __________________ 5: Make the Grip the Proper Thickness, Shape, and Length __________________ 6: Make the Grip Surface Smooth, Compressible, and Nonconductive __________________ 7: Consider the Angles of the Forearm, Grip, and Tool 8: Use the Appropriate Muscle Group __________________

3 ISE 311 Guideline 1: Use Special-Purpose Tools Benefit: Performs well tasks that are repeated many times/week Costs: Capital, maintenance, utility Analysis:  Estimate years of use and usage/year  Divide total cost by usage  Compare to savings Tool Selection 1. Whether a tool is expensive depends on a detailed analysis, not just capital cost. 2. Benefits include savings beyond just labor savings (capability, quality, etc.)

4 ISE 311 Handtool Selection Steps 1. Do a job analysis. 2. Identify tool-use issues:  Operating forces  Repetitions per minute or per shift  Postures 3. Select the right tools.

5 ISE 311 Guideline 2: Design Tools to Be Used by Either Hand The tool should be in the user’s preferred hand. Strength, dexterity, and performance are greater for the preferred hand. Benefits:  Includes the 10% of the population that is left- handed.  Allows nonpreferred hand to be used when the preferred hand is engaged or resting.

6 ISE 311 Handgrip Strengths

7 ISE 311 Gloves Protect the hand against abrasion, impact, chemicals, heat, cold, cuts, infection, vibration. May decrease manual dexterity and increase assembly time. Decrease force grip.

8 ISE 311 Guideline 3: Power with Motors More Than with Muscles Mechanical energy is 10 to 1000 times cheaper than human. Motors extend capability and do not fatigue. Motors permit a larger percent of workforce to do the job. Reducing Hand–Arm Vibration Syndrome  Use a process with zero or low operator vibration.  Use equipment with low levels of vibration.  Use equipment with vibration-isolated handles.  Avoid resonance.  Furnish vibration-isolated gloves.  Encourage workers to follow VS-reducing practices.

9 ISE 311 Guideline 4: Use the Proper Grip Power grip  Tool handle perpendicular to the forearm axis.  Direction of force: Parallel to forearm At an angle to forearm Applied as torque about forearm Semipower grip  Fingers act as a group but thumb position changes.  Oblique or hook grip Hook grips are preferable to pinch grips. Precision grip  About 20% strength of a power grip.  Internal (table knife) or external (pencil) precision grip  Forearm or tool may be supported

10 ISE 311 Examples

11 ISE 311 Guideline 5: Make the Grip the Proper Thickness, Shape, and Length Hand Sizes  Are larger with gloves.  Tend to be larger for men than for women. Grip Diameter  For power grip, 35 mm to 45 mm is optimal.  For precision grip, use 9.5 mm to 12.7 mm.

12 ISE 311 Grip Shape Section Perpendicular to Grip Axis  Prevent rotation and slippage.  Use thumb conoid or noncircular cross-section.  Improve coefficient of friction of handle. Section Along Tool Grip Axis  Keeps tool from moving forward and backward in hand.  Allows force exerted along tool axis to be greater.  Can act as a shield. Length  For power grip, all fingers must make contact.  For external precision grip, shaft must be supported.  For internal precision grip, tool must extend past palm but not as far as wrist.

13 ISE 311 Guideline 6: Make the Grip Surface Smooth, Compressible, & Nonconductive Smoothness reduces pressure points. Compressibility minimizes pressure on the hand. Nonconductivity reduces heat and cold problems and risk of electric shock.

14 ISE 311 Guideline 7: Consider the Angles of the Forearm, Grip, & Tool Angle  Keep the wrist in neutral position.  Best angle varies with posture.  Consider changing the job to improve angle.  Consider pistol-grip or bent tools. Clearance  Increase distance from hot surfaces to reduce burns.  Provide shield from heat.  A narrow neck reduces heat transfer.  Avoid pinching risk with repetitive-use tools.

15 ISE 311 Examples

16 ISE 311 Guideline 8: Use the Appropriate Muscle Group Muscle Direction  Strengths and ranges of motion differ.  Consider normally-open tools.  Give muscle something to push against. Muscle Size  Consider moment arm.  Provide power grip.

17 ISE 311 Guideline 8 (cont.) Use the Appropriate Muscle Group One versus Many  Use fingers in combination.  Pinch types vary greatly in strength.  Consider trigger strips instead of buttons.  Consider alternate types of triggers. Rotate Inward  Right hand and arm can rotate 70º clockwise, 150º counterclockwise. Muscle Time  Reduce time the muscle is used.  Use clamping tools, locking triggers, discrete controls, straps.  Consider guides or funnels for positioning.