Understanding Gear Addendum

In gear terminology, the addendum refers to the radial distance from the pitch circle to the top land (outermost surface) of a gear tooth. It's a crucial dimension in gear design that determines the overall height of the tooth above the pitch line.

Explaining the Standard Addendum Value

The size of a gear tooth is often related to its module (m). The module is a measure of the tooth size, defined as the pitch diameter divided by the number of teeth.

For standard spur gears, the addendum is typically defined as being equal to one module. This standard convention simplifies gear calculations and ensures interchangeability between gears made by different manufacturers.

Mathematically, the addendum ($a$) is related to the module ($m$) by the formula:

$a = 1 \times m$

Therefore, the standard value of the addendum is 1 module.

Analyzing the Options

Let's look at the given options:

• 1. 2 module
• 2. 1.157 module
• 3. 1 module
• 4. 3 module

Based on standard gear design practices, the addendum is equal to the module. Option 3 correctly states this standard value.