Bearing Inner Race: Roundness ≤ 0.003 mm

Component Specifications

Definition

The bearing inner race is a precision-engineered annular component that serves as the inner track for rolling elements (balls or rollers) in a bearing assembly. It is mounted directly onto the rotating shaft and provides the critical interface between the shaft and the bearing's rolling elements. Its primary functions include distributing radial and axial loads, maintaining precise alignment, reducing friction through rolling contact, and ensuring smooth rotational motion under various operating conditions. The inner race's geometry, surface finish, and material properties are optimized to withstand cyclic stresses, prevent premature wear, and maintain dimensional stability throughout the bearing's service life.

Working Principle

The bearing inner race operates on the principle of rolling contact mechanics. When mounted on a rotating shaft, it rotates with the shaft while providing a hardened, smooth raceway for the rolling elements. As the shaft rotates, the rolling elements roll between the inner race and outer race, converting sliding friction into significantly lower rolling friction. This reduces energy loss, heat generation, and wear. The inner race transfers loads from the shaft to the rolling elements, which then distribute those loads to the outer race and housing. Its precise geometry ensures proper contact angles and load distribution, while its interference fit with the shaft prevents relative motion that could cause fretting wear.

Materials

Typically made from through-hardened or case-hardened alloy steels such as AISI 52100 (chrome steel), AISI 440C (stainless steel for corrosion resistance), or AISI 8620 (case-hardening steel). Advanced applications may use ceramic materials (silicon nitride) for high-speed or high-temperature environments. Material specifications include hardness of 58-65 HRC for steel races, surface roughness Ra ≤ 0.2 μm, and strict control of microstructural properties like carbide distribution and retained austenite content.

Technical Parameters

Parameter	Typical range	Notes & selection driver
Roundness	≤ 0.003 mm
Concentricity	≤ 0.005 mm
Inner Diameter	Precision-ground to h5 or h6 tolerance
Outer Diameter	Ground to precise dimensions for proper clearance
Surface Finish	Ra ≤ 0.2 μm on raceway
Surface Hardness	58-65 HRC
Raceway Curvature	0.52-0.54 times ball diameter for deep groove bearings
Chamfer Dimensions	Specified per bearing type

Ranges are indicative industry figures for RFQ preparation, not a supplier commitment. Confirm every value and standard with the legal manufacturer before ordering.

Standards

ISO 15, ISO 492, DIN 620, ABMA 20, JIS B 1514

Parent Products

This component is used in the following industrial products

Drive Shaft & Bearings

A mechanical assembly that transmits rotational power from the motor to the centrifugal wheel while supporting radial and axial loads.

View Product Details

Engineering Analysis

Risks & Mitigation

Fatigue spalling from cyclic loading
Brinelling from shock loads
Fretting corrosion at shaft interface
Thermal cracking from overheating
Micro-pitting from inadequate lubrication
Electrical erosion in VFD applications

FMEA Triads

Trigger: Improper interference fit during installation
Failure: Cracking or fracture of inner race, loss of press fit leading to shaft rotation relative to race
Mitigation: Follow manufacturer's installation guidelines, use proper tools, verify fit tolerances, apply appropriate mounting force

Trigger: Inadequate lubrication or lubricant contamination
Failure: Surface distress, micro-pitting, accelerated wear, increased operating temperature
Mitigation: Implement proper lubrication schedules, use correct lubricant type and quantity, maintain clean lubrication systems, monitor lubricant condition

Trigger: Misalignment between shaft and housing
Failure: Uneven load distribution, edge loading, premature fatigue, increased vibration
Mitigation: Ensure precise alignment during installation, use alignment tools, verify runout tolerances, implement regular alignment checks

Industrial Ecosystem

Compatible With

Typical Suppliers & Equivalents

Compliance & Inspection

Tolerance

Inner diameter tolerance: ISO h5 or h6 (typically ±0.004-0.008 mm depending on size), raceway profile tolerance: ≤ 0.003 mm, surface roughness: Ra ≤ 0.2 μm

Test Method

Dimensional verification using coordinate measuring machines (CMM), surface roughness testing with profilometers, hardness testing with Rockwell or Vickers methods, microstructure analysis, non-destructive testing (magnetic particle or ultrasonic) for defects, rotational accuracy testing on precision spindles

Procurement Evaluation Criteria

A practical evidence checklist for RFQ preparation and supplier evaluation.

Technical documentation

Request current drawings, revision history, and a signed specification sheet.

Manufacturing capability

Verify equipment lists, process limits, capacity, and representative production evidence.

Inspection readiness

Confirm test methods, calibrated equipment, sampling plans, and traceable reports.

Supplier transparency

Check the legal entity, factory address, ownership, certifications, and direct contacts.

CNFX does not score or rank suppliers. Buyers must verify all claims and documents with the legal manufacturer before ordering.

Manufacturers of Bearing Inner Race

Manufacturer profiles associated with Bearing Inner Race.

Sourcing Bearing Inner Race from China?

Tell us your specification and target quantity — we will match it against manufacturer records and come back with the factories that fit.

Request manufacturers We manufacture this

Manufacturer listings support early research and capability understanding. They are not certification, ranking, or transaction guarantees.

Related Components

Chrome Plating

Hard chrome plating is an electroplating process that deposits a layer of chromium onto metal surfaces to enhance wear resistance, corrosion protection, and reduce friction for hydraulic cylinder piston rods.

Upper Tool (Punch)

Upper Tool (Punch) is the active forming component in metal plate bending machines that applies precise downward force to create bends in sheet metal.

Main Frame

The main frame is the primary structural component of a hydraulic press, providing rigidity and stability to withstand high compressive forces during metal forming operations.

Shaft Bearing

Precision component supporting rotating shafts in vibration motors to reduce friction and maintain alignment.

Frequently Asked Questions

What is the difference between bearing inner race and outer race?

The inner race rotates with the shaft and has an interference fit, while the outer race is stationary in the housing with a clearance fit. The inner race typically experiences higher stress concentrations due to its smaller diameter and direct connection to the rotating shaft.

How is the bearing inner race mounted on the shaft?

It is typically mounted using an interference fit (press fit) to prevent relative motion. Installation methods include hydraulic pressing, mechanical pressing, or thermal expansion (heating the race before mounting). Proper mounting force and alignment are critical to prevent damage.

What causes premature failure of bearing inner races?

Common causes include improper installation (misalignment, excessive force), inadequate lubrication, contamination ingress, excessive preload, fatigue from cyclic loading, corrosion, and electrical arcing in electrically charged environments.

Data Basis

Editorial classification, named public sources where available, and source-reviewed manufacturer records. See the editorial policy.

Preliminary Technical Classification

This page supports structured research, RFQ preparation, and supplier evaluation. It does not replace buyer-led supplier qualification, standards review, or technical approval.

Bearing Inner Race