Chapter 6 Design of Keys, Splines and Pins

Key terms:• Keys • Splines • Keyway, keyseat • Hub • Crush • Pin

6.1 Key Joints

• 1. Basic Concept A key is a fastening inserted into the keyway of two mating parts, it is used to transmit torque from a shaft to a hub or vice versa.

2. Types of Keys

• Straight keys

• Woodruff keys

• Taper keys

• Splines

3. Straight Key Joints

• 1) Principles clearance

2) Types

a. Plain flat keys 普通平键 (fixed joints)

A Key with rounded ends

B Key with square ends

C Key with one square and one rounded end

b. guided keys (sliding joints)

c. feather key joints (sliding joints)

4.Woodruff Key Joints

Greater depth of the key seat in the shaft.

5. Taper Key Joints

Gib-head taper key

Tangent Double-taper Key Joints

6. Strength Calculation of Straight Key Joints

1)Failure Modes: crush, wear, snip

T——torque

d——diameter of shaft

h——thickness of the key

l——working length of the key

[p]——allowable crush stress

2)Crushed Strength Condition

][dhl

T4p

3) Steps for Selecting Straight Keys

• a. According to the diameter of shaft, get section size

b h;

• b. Select proper key length L in key length series;

• c. Check the Strength Calculation (if necessary);

h

L b

4) Double-Keys Arrangement

6.2 Splines Joints • Splines can be dealt as multiple keys w

hich are integral with the shaft.Splines are classified as: Parallel-sided splinesInvolute splines

Advantages: 1) Greater carrying capacity; 2) Greater fatigue strength of a spline shaft; 3) More accurately centered and guided.

Disadvantages:

Requirements for special equipments and tools, which increase the manufacturing costs.

6.3 Pin Joints

Cylindrical pin Taper pin Pin for joining

safety pin

Key Standards

The endThanks!