I. Core Features and Identification of HK Bearings
Structure: Only ball bearings and cages, without inner rings and outer rings.
Code rule: The code is usually HK + size number, for example, HK 1012.
HK represents the metric series of needle roller bearings without inner rings.
10 represents the inner diameter (i.e., the diameter of the shaft) and d = 10 mm.
12 represents the outer diameter, D = 12 mm.
Core value: Despite the extremely limited radial space, achieve extremely high radial load-bearing capacity.
II. The Outstanding Advantages of HK Bearings
Exceptional Compactness (Core Advantage): Due to the elimination of the inner ring, at the same shaft diameter, the cross-sectional height of HK bearings is the smallest among all rolling bearings. This makes it an ideal choice for applications with limited space.
High radial load capacity: By using needle rollers as the rolling elements, which are in line contact, the radial load capacity of this type of bearing is much greater than that of ball bearings of the same size.
Lightweighting: Simple structure, few parts, and low weight.
Economy: The cost is relatively low by itself, and since it allows the use of thicker shafts, it sometimes enables the simplification of the design of adjacent components.
III. Limitations of HK Bearings (Installation Requirements)
The use of HK bearings comes with a cost. They have very strict requirements for their installation environment:
Unable to withstand any axial load: HK bearings can only bear pure radial loads. Any axial load must be borne by other bearings (such as deep groove ball bearings).
The requirements for the shaft and the bearing housing are extremely high (the most crucial point):
The hardness of the shaft: Since there is no inner ring, the shaft neck surface will serve as the raceway directly. Therefore, the shaft neck must be hardened to a hardness of no less than HRC 58, and the surface needs to be ground to have the same hardness and finish as the inner ring of the bearing.
The accuracy of the bearing housing: The bearing housing hole needs to serve as the raceway for the outer ring, so its diameter tolerance, roundness, cylindricity, and surface roughness must also meet the requirements of a precision bearing housing.
Sensitive to skew: Due to the long length of the balls, even a slight misalignment of the axis can lead to stress concentration, thereby affecting the lifespan.
The maximum rotational speed is relatively low: typically lower than that of ball bearings of the same size.
IV. Typical Application Scenarios of HK Bearings
HK bearings are suitable for situations where space is limited, they need to withstand heavy radial loads, and the rotational speed is low.
Automobile sector:
Piston pin: This is the most classic application. The small end hole of the connecting rod serves as the bearing seat, the piston pin acts as the shaft, and the HK bearing connects the two, resulting in an extremely compact structure.
Washing machine: The deceleration clutch of a top-loading washing machine.
V. User Guide for HK Bearings (Selection and Installation Steps)
Step 1: Determine if HK bearings are suitable for use
Ask yourself the following questions:
Is the radial space extremely crowded? (Yes → Suitable)
Is the load purely radial? (Yes → Suitable)
Can I quench and grind the journal to a hardness of HRC 58 or above? (Yes → Suitable)
Is the rotational speed requirement high? (Not high → Suitable)
If the answers above are mostly "yes", then HK bearings are an excellent choice. Otherwise, standard needle roller bearings with inner rings or deep groove ball bearings should be considered.
Step 2: Selection of Components and Tolerance Matching
Choose the inner diameter of the bearing based on the shaft diameter d: The inner diameter code of the HK bearing (such as 10) is the shaft diameter (10mm) that you need to design.
Based on the space of the bearing housing, select the outer diameter of the bearing: The outer diameter D (e.g. 12) determines the size of the bearing housing hole.
Determine the tolerances of the shaft and the seat: This is the technical core. The tolerance of the shaft is usually selected as k5 or j5 to achieve a slight interference fit, preventing sliding wear between the shaft and the needle rollers. The tolerance of the bearing seat hole is usually selected as H6 or G6.
Step 3: Installation Precautions
Cleaning: Before installation, ensure that the shaft neck, bearing seat holes, and the bearings themselves are absolutely clean.
Lubrication: Before installation, sufficient lubricating grease must be applied to the shaft neck and the rolling pins of the bearing. HK bearings usually require oil lubrication or grease lubrication.
Smooth insertion: Use a special tool to insert the bearing smoothly into the bearing housing hole. Do not strike the bearing directly to avoid damaging the cage.
Post-installation inspection: After installation, the shaft should be able to be rotated easily by hand without any resistance.
Summary
HK bearings are high-performance components specifically designed for extremely compact spaces. Their application is more akin to a "precise design" rather than a "simple replacement". By elevating the installation base (the shaft and the bore) to become part of the bearing raceway, they maximize the utilization of space. If you can meet their demanding requirements for hardness and precision, it will bring unparalleled performance advantages; if not, forcing their use will result in rapid failure.
Key tip: When using HK bearings, make sure to properly handle your shaft and housing first.
Shell Bearings
CAGE GUIDED NEEDLE ROLLER
BEARING SERIES
Drawn cup
Combined inch and metric sizes
Open for through shafts
Closed for shaft ends
For details on part numbers, descriptive suffixes and various technical references, please refer to front of this section.
For engineering or technical information contact your local sales representative or call Distributor Sales (800)523-6572.
