Splines
Splines
• A spline is a series of axial keys on a shaft, with
corresponding grooves on the bore of the mating part.
• Splines transmit torque from the shaft to the mating
element, similar to keys.
• Advantages of splines over keys include more uniform
torque transfer, lower loading, no relative motion
between spline and shaft, and controlled fit between
internal and external splines.
• Splines are accurately machined to provide a controlled
fit between mating internal and external splines, and
the surface is often hardened to resist wear
POWER AND FORCE FOR SPLINE
Bearing Stress for a Spline
Spline Shear Stress
Formulas for SAE Straight Splines
• The torque capacity for SAE splines is based on the limit of 1000
PSI bearing stress on the sides of the splines, for which the
following formula is derived
A 10-spline shaft ( d= 0.91D, w= 0.156D, h= 0.045D ) and permanent fit has a diameter of 70
mm. Find the shearing stress if force applied is 2000 lbs. Hub length is 120 mm.
Specify a suitable spline having a B fit for a gear to be mounted on a shaft with a 2.00 in
diameter. The gear transmits 3100 lb-in of torque and has a hub length of 4.00 in.
𝟐 𝟐
Pinning
• With the element in position on the shaft, a hole can be drilled through
both the hub and the shaft, and a pin can be inserted in the hole.
Pinning
The straight, solid, cylindrical pin is subjected to shear over
two cross sections.
Set Screws
• A set screw is a threaded fastener used to secure a shaft.
• The point of the set screw can have different shapes and
bears on the shaft's surface.
• Torque is transmitted through friction or shear
resistance between the point and the shaft.
• Torque transmission capacity varies based on shaft
hardness and clamping force.
• Set screws may loosen due to vibration and should be used carefully.
• Some set screws have plastic inserts or can be secured with liquid adhesive to
resist loosening.
• Set screws can cause damage to the shaft surface, making disassembly difficult.
• Machining a flat surface on the shaft can reduce damage and improve
assembly consistency.
Set Screws
• When set screws are properly assembled on typical
industrial shafting, their force capability is
approximately as follows
