For gears to mesh properly, what must they have in common?

For gears to mesh properly, they must have the same diametral pitch and pressure angle. The diametral pitch refers to the number of teeth per inch of the gear's pitch diameter, which directly affects the size of the teeth and how well they interlock. The pressure angle is the angle between the line of action (the path along which the force is transmitted between the gears) and a line perpendicular to the line connecting the centers of the gears. When gears share the same diametral pitch, it ensures that their teeth will properly align and mesh without slipping or binding.

Additionally, having the same pressure angle is crucial for maintaining smooth engagement and disengagement of the gear teeth during operation. If gears with different pressure angles are used together, they may not mesh correctly, leading to increased wear, potential damage, and reduced efficiency in the gearing system.

While characteristics like size, shape, color, and material can influence gear performance and compatibility, they are not the primary technical requirements for proper meshing. Instead, focusing on the diametral pitch and pressure angle ensures the mechanical relationship necessary for effective gear operation.