Beveled Disk Cam to Rod Mechanism: How It Works, Diagram, Formula, and Uses Explained

An inclined face drives a guided rod

The shaft rotates a disk whose working face is inclined to a plane normal to the shaft. A follower at a fixed offset samples that face. As the high and low parts pass beneath it, the rod moves along its guide. Hiscox’s oblique-disc movement 1085 shows this arrangement with a guided rod and roller.

This calculator uses an ideal point-contact follower rather than calculating a finite roller envelope. The drawing includes a return spring to explain how contact can be maintained. Its shape is illustrative; it is not a calculated spring design. Adequate contact force is an assumption of the motion calculation.

Studying axial reciprocation

The arrangement is useful for understanding rotary-to-axial motion. A rotating inclined face and a stationary inclined plate with rotating followers are different constructions, even when related stroke equations appear. The animation here shows the former: the rod’s guide remains fixed while the disk rotates.

Stroke, velocity and acceleration

Let R = D / 2, where D is contact-track diameter, and let θ be the disk-face inclination from a plane perpendicular to the shaft. With shaft angle φ, displacement from the mean is z = R tan θ cos φ. The full stroke is therefore S = 2R tan θ = D tan θ.

At n revolutions per minute, ω = 2πn / 60. Velocity is −Aω sin φ and acceleration is −Aω² cos φ, where A = S / 2. Their peak magnitudes are Aω and Aω². Continuous contact is assumed; neither acceleration nor speed alone establishes the spring force needed to prevent separation.

Worked diameter-based example

Use a 40 mm contact-track diameter, 18° inclination and 90 rpm shaft speed. The radial offset is 20 mm. Full stroke is 40 tan 18° = 13.00 mm and amplitude is 6.50 mm. Angular speed is 9.425 rad/s, giving peak velocity about 61.2 mm/s and peak acceleration about 577 mm/s².

Using 20 mm in the diameter formula would incorrectly halve these results. Doubling speed doubles peak velocity and quadruples peak acceleration; it does not change stroke.

What the sinusoidal model omits

The model gives geometry and kinematics, not contact force, spring sizing, wear, friction, stiffness or a permissible operating speed. A finite roller or a follower inclined to the shaft requires its own contact geometry. The simple plane gives continuous rise and fall without a finite dwell.

Inclined-disk questions

Is the diameter the outside diameter of the disk?

No. It is twice the radial offset of the follower axis. The physical disk must cover that track through the complete rotation.

Where is the inclination measured?

From a plane perpendicular to the shaft. Zero inclination would give a flat normal face and no stroke.

Does the animation prove the follower stays in contact?

No. Maintained contact is assumed. Actual spring force, moving mass and external loads must be checked separately.

Does doubling speed double the stroke?

No. Stroke depends on diameter and inclination. Speed changes cycle frequency, velocity and acceleration.