Cam Follower Selection Guide: Loads & Stress Formulas

Figure 1: Standard Stud Needle Roller Cam Follower anatomy.

Needle Roller Cam Followers

Needle Roller Cam Followers feature a heavy outer ring cross-section and a full complement of needle rollers. They provide high dynamic and static load-carrying capability and anti-friction performance in a compact footprint. These components are essential as track rollers, cam followers, and in a wide array of linear motion systems.

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• Standard Stud: Threaded stud mounting for moderate loads. Available with crowned outer rings to mitigate misalignment.
• Heavy Stud: Enhanced stud strength for high-shock or heavy-duty loading applications.
• Yoke Type: Ideal for loads exceeding stud capabilities. Clevis mounting provides dual-side support via a high-strength pin.
• CamCentric®: Adjustable design for precision positioning; perfect for eliminating backlash.
• Crowned Outer Rings: Optimized for curved tracks or skewed travel directions to minimize thrusting.

Technical Comparison: Cam Followers vs. Standard Bearings

1. Structural Differences

Standard ball and roller bearings are typically mounted in rigid housings that support the entire circumference. Consequently, forces are transmitted directly into the housing without significant ring deformation.

In contrast, cam followers are supported at a single point. Individual roller forces generate bending moments on the outer ring around this contact point. This results in ring deformation, reversed bending stresses, and a concentrated load zone (see Fig. 2).

Figure 2: Load zone distribution and contact stress concentration.

2. Capacity and Load Limits

Service life evaluation for cam followers must account for rolling element capacity, outer ring deformation, track capacity, and stud bending stress. For best results, operating loads should not exceed 50% of the dynamic capacity.

2.1 Track Capacity

Track capacity is the load a track can withstand without plastic deformation. The standard baseline is HRc 40.

Figure 3: Understanding Hertzian stress distribution in point-contact loading.

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Table 1: Track Capacity Modification Factors
Track Hardness [HRc]	Tensile Strength [psi]	Capacity Factor
26	128,000	0.45
32	146,000	0.61
36	165,000	0.79
40	180,000	1.00
44	208,000	1.24
50	247,000	1.58
54	281,000	1.94
58	312,000	2.35
60	335,000	2.60

2.2 Stress Equations

Steel-on-Steel Contact Stress (RBC Standard):

σ_{c max} = 3237 × √

F

l_eff × D

[psi]

General Hertz Contact Stress (Roark):

σ_{c max} = 0.591 × √

F × E

D × w

2.3 Bending and Shear Stresses

Assuming a tight mount, the concentrated force F generates a bending moment M_b:

M_b = F × (

B

2

+

1

32

)

Figure 4: Bending moment diagram for stud type cam follower.

2.4 Yoke Roller Pin Shear Stress:

τ_shear =

2 × F

π × PD²

Source: RBC Bearings

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Advanced Cam Design Resources

• Timing Diagram (Part 1)
• Acceleration Analysis
• Cycloid Cam Profiles
• Polynomial Functions
• Fifth-degree Derivation
• Polynomial Excel Tools