Camdiameter

Camdiameter is a term used in cam mechanisms to denote the diameter of the driving cam surface that engages the follower. In radial and cylindrical cams, this diameter establishes the scale of the follower’s motion and the basic contact geometry between the cam and its follower.

The exact meaning of camdiameter varies by author and industry practice. In many classical references, camdiameter refers to the base circle diameter—the diameter of the circle tangent to the cam profile at the start of motion. In other contexts, it may be used to describe the outer diameter of the cam itself, which can differ from the base circle when lobes are present or when profile offsets are applied. Because conventions differ, it is important to consult the specific design documentation or CAD model for clarification.

Relation to design and analysis: The base radius rb = camdiameter/2 defines the reference circle from which the cam profile is drawn. The follower displacement at a given cam rotation angle θ is s(θ) = r(θ) − rb, where r(θ) is the radial distance from the cam center to the profile at θ. The camdiameter thus influences the potential lift, velocity, acceleration, and contact stresses in the mechanism, as well as the pressure angle and overall dynamic behavior.

Measurement and design practice: In CAD models, camdiameter is specified as the base circle diameter, with the profile built around rb. In manufacturing or inspection, measurements may use coordinate measurement equipment to verify the base circle and the actual profiling against the intended lift function.

See also: cam mechanism; base circle; cam profile; follower.