Introduction to Gear Rack Structure

Tooth (Teeth): Each protruding part on a gear used for meshing.

Generally, these protrusions are arranged radially.

The teeth on mating gears contact each other, resulting in continuous meshing and rotation of the gears.

Tooth Space: The space between two adjacent teeth on a gear.

Gear End Face - On a cylindrical gear or cylindrical worm, the plane perpendicular to the axis of the gear or worm.

Normal Plane: On a gear, the normal plane refers to the plane perpendicular to the tooth line.

Addendum Circle: The circle where the tooth tips are located.

Root Circle: The circle where the bottoms of the tooth spaces are located.

Base Circle: The circle on which the generating line of the involute rolls purely.

Pitch Circle: The reference circle within the end face for calculating the gear's geometric dimensions. For spur gears, the module and pressure angle are standard values on the pitch circle.

Tooth Surface: The side surface of a tooth located between the addendum cylinder and the root cylinder.

Tooth Profile: The intersection of the tooth surface with a specified surface (a plane for cylindrical gears).

Tooth Line: The intersection of the tooth surface and the pitch cylinder.

Circular Pitch (pt): The arc length on the pitch circle between two adjacent tooth profiles on the same side.

Module (m): The quotient obtained by dividing the circular pitch by π, measured in millimeters.

Diametral Pitch (p): The reciprocal of the module, measured in inches.

Tooth Thickness (s): The arc length on the pitch circle between the two tooth profiles on one tooth on the end face.

Space Width (e): The arc length on the pitch circle between the two tooth profiles of a tooth space on the end face.

Addendum (hɑ): The radial distance between the addendum circle and the pitch circle.

Dedendum (hf): The radial distance between the pitch circle and the root circle.

Whole Depth (h): The radial distance between the addendum circle and the root circle.

Tooth Width (b): The dimension of the tooth along the axial direction.

Transverse Pressure Angle (ɑt): The acute angle between the radial line passing through the intersection of the tooth profile and the pitch circle on the end face and the tangent to the tooth profile at that point.

Standard Rack: A rack whose base circle dimensions, tooth shape, whole depth, addendum, and tooth thickness all conform to standard spur gear specifications. A rack cut according to these specifications is called a standard rack.

Standard Pitch Circle: The reference circle used to determine the dimensions of various parts of a gear. It is equal to the number of teeth multiplied by the module.

Standard Pitch Line: A specific pitch line on a rack, or the tooth thickness measured along this line, which is half the pitch.

Action Pitch Circle: When a pair of spur gears mesh, each has a tangent rolling circle.

Standard Pitch: Based on a selected standard pitch, equal to the pitch of the standard rack.

Pitch Circle: The locus of the points of contact between the teeth of two meshing gears on the line connecting their centers.

Pitch Diameter: The diameter of the pitch circle.

Working Depth: The sum of the addendums of a pair of spur gears. Also known as working depth.

Addendum: The difference between the radius of the addendum circle and the pitch circle.

Backlash: The gap between the tooth surfaces when two teeth mesh.

Clearance: The gap between the addendum circle of one gear and the root circle of the other gear when the teeth mesh.

Pitch Point: The point of tangency between a pair of meshing gears and their pitch circles.

Pitch: The distance along the arc between corresponding points on adjacent teeth.

Normal Pitch: The pitch measured along a specific cross-section perpendicular to the tooth line of an involute gear.

Introduction to Plastic Gears: With the development of science, gears have gradually transitioned from metal gears to plastic gears. This is because plastic gears have better lubricity and wear resistance.

They can reduce noise, lower costs, and reduce friction.

Commonly used plastic gear materials include: POM, PTFE, PA, nylon, PEEK, etc. Gear structural design mainly determines the structural form and size of the gear rim, hub, and web (spokes).

Structural design usually considers factors such as gear geometry, material, usage requirements, processability, and economy to determine a suitable structural type, and then determine the structural dimensions according to the empirical data recommended in the design manual.