Center-to-center Distance

Center-to-center distance, abbreviated as CC, also called center distance, is the distance between the axes (centers) of two gears that are meshing with each other.  It is the measurement from the center of one gear to the center of the mating gear.  This distance is critical in gear design and is used to determine the positioning of gears within a mechanical system.

key points about center-to-center distance in gear systems

• Meshing Gears  -  The center-to-center distance is a crucial parameter when designing gear systems because it influences the proper meshing of gears.  Gears need to be positioned at the correct distance from each other to ensure smooth and effective power transmission.
• Pitch Circles  -  The pitch circle is an imaginary circle used in gear design that represents the point where gears effectively mesh.  The center-to-center distance is measured along the line of action, which is the line along which the gears exert force on each other.
• Gear Ratio Consideration  -  The center-to-center distance is essential for maintaining the desired gear ratio between meshing gears.  The gear ratio is determined by the number of teeth on each gear, and the center-to-center distance influences the proper alignment for accurate transmission of motion.
• Axial Positioning  -  In addition to influencing the gear ratio, the center-to-center distance is important for proper axial positioning of gears.  The correct axial alignment ensures that the gears engage with each other smoothly and efficiently.
• Design Considerations  -  When designing a system with gears, engineers need to carefully consider the center-to-center distance along with other parameters such as the diameters of the gears, the number of teeth, and the overall layout of the machinery.

 

Center-to-center Distance formula
\( CC \;=\;  (PD_a + PD_b) \;/\; 2 \)     (Center-to-center Distance) \( PD_a \;=\; 2 \; CC - PD_b \) \( PD_b \;=\; 2 \; CC - PD_a \)
Symbol	English	Metric
\( CC \) = center-to-center distance	\(in\)	\(mm\)
\( PD_a \) = pitch diameter gear a	\(in\)	\(mm\)
\( PD_b \) = pitch diameter gear b	\(in\)	\(mm\)