Components used to securely mount power transmitting elements on a shaft'

1
Shafts Accessories

• Components used to securely mount power
  transmitting elements on a shaft.

• Axial
• Rotational

2
Keys

• Allow torque to be transferred from a shaft to a
  power transmitting element (gear, sprocket,
  sheave, etc.)

3
Key Design

• Use a soft, low strength material
• (ie, low carbon steel)
• Standard size HW1/4 D
• Design length
• based on strength

4
Standard Key Sizes
5
Key Design

• Key Shear
• Failure Theory
• Length

6
Example

• Specify a key for a gear (grade 40, gray cast
  iron) to be mounted on a shaft (AISI 1144, hot
  rolled) with a 2.00 in. diameter. The gear
  transmits 21000 lb-in of torque and has a hub
  length of 4 in.

7
Retaining Rings

• Also known as snap rings
• Provides a removable shoulder to lock components
  on shafts or in bores.
• Made of spring steel, with a high shear strength.
  
• Stamped, bent-wire, and spiral-wound.

8
Retaining Ring Selection

• Based on shaft diameter thrust force

9
Set Screws

• Setscrews are fasteners that hold collars,
  pulleys, or gears on shafts.
• They are categorized by drive type and point
  style.

10
Standard Set Screw Sizes
11
Set Screw Holding
12
Pins

• A pin is placed in double shear
• Holds torsion and axial loads

• Hole is made slightly smaller than the pin (FN1
  fit)

13
Example

• Specify a pin for a gear (grade 40, gray cast
  iron) to be mounted on a shaft (AISI 1144, hot
  rolled) with a 2.00 in. diameter. The gear
  transmits 21000 lb-in of torque and has a hub
  length of 4 in.

14
Roll Pins

• Easier disassembly

15
Collars

• Creates a shoulder on shaft without increasing
  stock size.
• Held with either set screw or friction (clamped)

16
Mechanical Couplings

• Couplings are used to join two shafts
• Rigid couplings are simple and low cost. But they
  demand almost perfect alignment of the mating
  shafts.
• Misalignment causes undue forces and accelerated
  wear on the shafts, coupling, shaft bearings, or
  machine housing.

17
Mechanical Couplings

• In connecting two shafts, misalignment is the
  rule rather than the exception. It comes from
  such sources as bearing wear, structural
  deflection, thermal expansion, or settling
  machine foundations.
• When misalignment is expected, a flexible
  coupling must be used.

18
Mechanical Couplings

• Selection factors include
• Amount of torque (or power speed)
• Shaft Size
• Misalignment tolerance