What are some common methods for axially positioning 68 series bearings on a shaft and in a housing bore- Cixi Bao Li Bearing Manufacturing Co., Ltd.

The 68 Series Deep Groove Ball Bearing is distinguished by its thin-section design (a high bore-to-outside-diameter ratio) and suitability for high-speed operation where radial space is limited. Ensuring its precise axial positioning on both the shaft and in the housing bore is paramount to achieving the required system running accuracy, rigidity, and service life. The choice of locating method is a critical engineering decision, directly impacting the bearing's performance under dynamic and complex loading conditions.

I. Inner Ring Axial Locating Methods on the Shaft

The inner ring, typically subject to a tight fit (interference fit) on the shaft due to rotating load, still requires mechanical features to prevent axial creep and ensure stability, especially under high-speed or reversing axial loads.

1. Shaft Shoulder and Locknut Assembly

The shaft shoulder is the most reliable and fundamental axial datum. The inner ring is abutted against a precisely machined radial face on the shaft.

Professional Advantage: Provides a rigid and stable reference plane. The shoulder height must be specified to clear the inner ring's corner chamfer radius (), ensuring full contact with the ring face. This setup is ideal for supporting significant unidirectional axial loads.
Application: Machine tool spindles, gearbox input/output shafts where high stiffness and precise alignment are essential.

The Precision Locknut (often paired with a locking washer or special anti-rotation device) is used on the opposite side to clamp the inner ring against the shoulder.

Professional Advantage: Delivers extremely high axial clamping force and allows for precise control of the bearing's axial preload, a necessity for optimizing the rigidity and running accuracy of a paired bearing set (e.g., DB or DF configurations).
Technical Consideration: Thread pitch and torque specifications must be strictly followed to achieve the designed preload without damaging the bearing or thread.

2. Spacer Rings and Labyrinth Seals

Spacer Rings are positioned between the inner rings of adjacent components (such as two bearings, a bearing and a gear, or a bearing and a sealing device).

Professional Advantage: Used to precisely establish the distance between bearing sets or components, ensuring accurate axial location when multiple parts are clamped together by a single end cap or locknut. They are critical for achieving the correct contact angle and load distribution in adjusted bearing arrangements.
Application: Multi-bearing arrangements where dimensional stack-up control is vital.

Labyrinth Seals often feature a wide flange or ring that also serves as a locating element, sitting against the inner ring and being held in place by an end component.

Professional Advantage: Combines axial location with non-contact sealing for high-speed operation, minimizing friction and heat generation.

II. Outer Ring Axial Locating Methods in the Housing Bore

The outer ring, often subject to a loose fit (clearance fit) in the housing to allow for thermal expansion or ease of assembly, requires robust means to restrict its axial movement within the bore.

1. Housing Shoulder and End Cover Retention

The Housing Shoulder provides the primary axial stop for the outer ring on one side. This machined step in the bore limits the ring's travel.

Professional Advantage: Offers high stiffness and reliable positioning, suitable for guiding the shaft and supporting external bi-directional axial forces (when used with an end cover on the opposite side). The bore diameter tolerance and perpendicularity of the shoulder face are crucial for overall system alignment.
Application: General industrial machinery, pump housings, and any system using the 68 Series as the designated locating bearing.

The Bearing End Cover (or Housing Cap) secures the outer ring from the open side of the bore, clamping it against the housing shoulder.

Professional Advantage: Facilitates a through-bore design in the housing, simplifying machining. Bolt torque control is necessary to ensure uniform clamping pressure and prevent outer ring distortion, which could compromise running precision.

2. Snap Rings (Retaining Rings) in Grooves

Snap Rings (or Circlips/Retaining Rings) are spring steel rings that sit in a pre-machined internal groove in the housing bore.

Professional Advantage: Highly space-efficient and cost-effective, particularly for the thin-section 68 Series where compactness is key. They offer a reliable axial stop without requiring bulky end covers.
Technical Consideration: Snap rings are primarily suited for light to moderate axial loads and should not be used in applications with heavy shock loading or high alternating axial forces, as they can deform or fail the groove. The groove depth and location must be precisely controlled relative to the outer ring face.

3. Threaded Rings and Adjusting Shims

A Threaded Ring (or Retaining Ring Nut) is screwed into a corresponding thread in the housing bore.

Professional Advantage: Allows for precise axial adjustment of the outer ring position during assembly. This method is often used to establish or fine-tune the running clearance or preload in a pair of mounted bearings.
Application: Housings where precise field adjustment is necessary, or where dimensional tolerance stack-up needs correction.

Adjusting Shims (Gaskets) are thin, flat rings of precise thickness placed between the outer ring face and an end cover or housing shoulder.

Professional Advantage: Simple, low-cost means to achieve fine axial tuning and ensure proper end play. They are particularly useful for compensating for manufacturing tolerances in the housing or shaft assembly.

III. Locating Bearing vs. Non-Locating Bearing Principles

A key design principle, especially relevant for the 68 Series in multi-bearing systems, is the distinction between the locating bearing and the non-locating bearing.

Locating Bearing: One bearing in the system is fully locked in the axial direction (both inner and outer rings are fixed), guiding the shaft and absorbing all external axial forces. The robust methods described above (shoulders, end covers, locknuts) are used.
Non-Locating Bearing: The second bearing must allow for axial float to compensate for the differential thermal expansion between the shaft and the housing. For the 68 Series, this is typically achieved by using a clearance fit for the outer ring in the housing, where the outer ring is restrained only by the friction of the fit or a very small gap between the end cover and the ring face. This freedom prevents the creation of detrimental internal stresses and premature bearing failure.