In the realm of linear motion and automation, the KR Series Needle Roller Bearing (commonly known as a Stud-Type Cam Follower) is a critical component that often goes unnoticed until it fails.
While it may look like a simple bolt with a wheel attached, the KR series is a sophisticated piece of engineering designed to bridge the gap between rotary and linear motion. Whether you are designing a high-speed packaging line or a heavy-duty conveyor system, understanding the specific mechanics of the KR series is vital.
Here is a technical breakdown of what makes the KR series unique.
1. The Anatomy: Stud-Type vs. Yoke-Type
The defining feature of the KR series is its "Stud-Type" construction. Unlike "Yoke-Type" track rollers (such as the NATR series) which require a separate shaft or pin for mounting, the KR series has a solid, threaded stud integrated directly into the bearing inner race.
- Why it matters: This allows for rapid installation. You simply insert the stud through a hole in your machine frame and secure it with a single nut.
- Engineering Note: The stud is specially heat-treated to withstand the shear stresses caused by cantilevered loads (since the load hangs off the side of the machine wall).
2. KR vs. KRV: The "Cage" Difference
One of the most common questions engineers ask is: "What is the difference between KR and KRV?"
- KR Series (Caged): The KR bearing contains a plastic or steel cage that separates the needle rollers. This reduces internal friction and heat generation, allowing the KR series to operate at higher speeds.
- KRV Series (Full Complement): The KRV series removes the cage and packs the race "full" of needle rollers. This maximizes load capacity but significantly lowers the maximum speed limit due to increased friction between rollers.
Selection Rule: If your application involves high-speed cam indexing or rapid transfer, choose the KR series. If you are moving massive loads slowly, choose KRV.
3. Mounting and Lubrication
Hex Socket: Modern KR series units typically feature a hexagonal socket in the stud head (and sometimes the tail) to hold the bearing in place while tightening the nut.
Lubrication: The stud contains internal oil paths with grease ports on the head and thread side, allowing for easy relubrication without disassembly.