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Table showing keyway / spline design factor Kd





Coupling Design Design Factor Kd
Fixed (close fit) loaded
No relative axial/radial movement of the hub and the shaft occurs.; the relative positions of the shaft and hub are fixed using a suitable bearing or constructional design e.g press-fit , Shaft nuts.
 1
Flexible/Sliding - Unloaded
Relative positions of the shaft and hub are not fixed; Axial movements of the hub along the shaft occur only when coupling is unloaded. The shaft is effectively fixed when loaded.
 3
Flexible/Sliding loaded
Sliding coupling with loading:relative positions of the shaft and hub are not fixed; axial shifts of the hub along the shaft occur in loaded couplings.
 9


Table showing spline application factors Ka



Power Source Type of Load
Uniform
Generators, Fans		 Light shock
Oscillating pumps		 Intermittent Shock
Actuators		 heavy shock
Presses, Shears
Application Factor (Ka
Uniform (Turbine, Motor) 1,0 1,2 1,5 1,8
light shock, (Hydraulic Motor) 1,2 1,3 1,8 2,1
Medium shock, (Internal combustion engine 2,00 2,2 2,4 2,8




Table showing splines distribution factors Km

This factor relates to reduction in strength as a result of misalignment of the spline



Misalignment (mm/mm Load misalignment factor (Km )
12mm face width 25mm face width 50mm face width 100mm face width
0,001 1,0 1,0 1 1,5
0,002 1,0 1,0 1,5 2,0
0,004 1,0 1,5 2,0 2,5
0,008 1,5 2,0 2,5 3,0


Table showing fatigue life factors for splines Kf



No of torque cycles
(stop/start cycles)		 Fatigue life factor (Kf )
Unidirectional Fully reversed
1 000 1,8 1,8
10 000 1,0 1,0
100 000 0,5 0,4
1 000 000 0,4 0,3
10 000 000 0,3 0,2


Table showing wear life factors for splines Kw



No revolutions of spline Life wear factor (Kf )
10 000 4,0
100 000 2,8
1 000 000 2,0
10 000 000 1,4
100 000 000 1,0
1000 000 000 0,7
10 000 000 000 0,5


Table showing Typical design strengths for selected materials



Material Hardness Ultimate
Tensile Strength		 Permissible
Compressive Strength		 Permitted
Shear Strength
Brinell Rockwell C MPa MPa MPa
Structural Steel 150-200 - 350 90 140
Carbon Steel 220-270 - 500 130 200
Alloy Steel 300-350 33-38 600 200 275
Surface Hardened Steel 650 45-53 650 250 275
Cast Iron
(Speroidal Graphite		 400 - 400 135 140



Sites Providing Relevant Information
  1. Mitcalc.com...Excel based programme allowing detailed design of shaft connection (19 Eur)
  2. Zakgear-Spline Stress Calculation... Calculator and associated equations of tables - Extemely useful - US units (not metric)
  3. Wikipedia _Spline Calcs in English Units... Extensive notes similar to Zakgear US units -not english
  4. Tasman industires...Supplier of keys
  5. Bonut Engineering...supplier of keys
  6. Technifast Ltd...Supplier of fasteners and keys.

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Last Updated 19/01/2013