1 Complete Model & Code Explanation

Model: 7015 CDGA/HCP4A

Code Definition

7015: Basic dimension of 70 series light-duty single-row angular contact ball bearing

CD: 15° nominal contact angle, machined solid brass cage optimized for extreme rotational speed

HC: Hybrid bearing design, silicon nitride Si₃N₄ ceramic rolling elements with steel inner and outer rings

GA: Factory end-ground duplex set, DB back-to-back arrangement with preset light preload

P4A: ISO P4 super precision grade with upgraded control standard for radial and axial runout

Supply form: Matched duplex set of two bearings with exclusive matching serial number

Important reminder: The matched duplex set must not be separated randomly. Cross mixing with bearings from other matching groups is prohibited. After separation, matching accuracy and factory preset preload will be permanently lost and cannot be restored. Only complete set installation is supported; on-site modification to DB/DF/DT layout is unavailable.

Suffix Comparison within Series

7015 CD/P4A: Single bearing, 15° contact angle, all steel balls, P4A precision, without duplex matching

7015 CDGA/P4A: Duplex set, 15° contact angle, all steel balls, GA light preload DB pairing

7015 CDGA/HCP4A: Duplex set, 15° contact angle, HC silicon nitride ceramic balls, GA light preload DB pairing (this model)

7015 CDGB/HCP4A: Duplex set, 15° contact angle, ceramic balls, GB medium preload DB pairing

Core Basic Dimensions

Bore d: 75 mm

Outer diameter D: 115 mm

Width B: 20 mm

Structure: Single-row open-type angular contact ball bearing, supplied as two matched DB back-to-back units

Rolling element: Silicon nitride Si₃N₄ ceramic balls (HC hybrid ceramic design)

Ring material: High-carbon chromium bearing steel, ultra-precision mirror grinding on raceway

Cage: Machined solid brass cage

Outer ring feature: Standard plain outer ring without integrated oil-air lubrication grooves

Pre-filled lubricant: None

Delivery form: Packaged as complete duplex set, engraved with unique matching serial number

Note: Official dynamic load rating and limiting DN data can be requested from manufacturer.

Full Product Attributes

Contact form: Two-point contact

Number of rows: Single row, factory pre-assembled as DB back-to-back duplex set

Pairing property: Permanently matched via factory end grinding, GA light preload; separation and random mixing forbidden

Precision class: P4A enhanced ISO P4 super precision high-speed grade

Material: Inner & outer rings: high-carbon chromium bearing steel; rolling elements: Si₃N₄ silicon nitride ceramic (HC hybrid)

Seal structure: Open type, non-sealed

Special construction: Hybrid ceramic rolling elements reduce centrifugal force and heat generation under high speed; precision end grinding ensures stable factory preset preload

Note: CD represents 15° small contact angle with prominent radial rigidity and moderate axial load capacity, featuring superior maximum rotational speed. Compared with steel balls, HC ceramic balls have lower density, greatly reducing centrifugal load at high speed, lowering contact stress on raceways, suppressing heat generation and raising DN limit. GA means standard light preload DB back-to-back duplex set, suitable for low-vibration finishing. Open construction supports oil-air lubrication and circulating oil lubrication; long-term continuous high-speed grease lubrication is not recommended. Factory pre-matched design simplifies assembly and fits mass-production spindle projects.

2 Structure & Operating Characteristics

Japan NMT 7015 CDGA/HCP4A is P4A super precision pre-matched duplex angular contact ball bearing of 7015 series with 15° contact angle and HC hybrid ceramic balls. Inner and outer rings adopt high-carbon chromium bearing steel with stabilized heat treatment to eliminate residual stress. Raceways are processed by repeated mirror super-finishing to achieve excellent rotational accuracy and low vibration.

Rolling elements are silicon nitride ceramic balls with light weight, high hardness and outstanding wear resistance. Centrifugal load under high-speed rotation is far lower than steel balls, reducing friction heat on raceways and improving temperature resistance. Matched machined solid brass cage maintains structural stability and deformation resistance under temperature rise for long-term nonstop high-speed operation.

Two bearings are end-ground and assembled into a DB back-to-back set at factory with preset GA light preload. Each set carries exclusive matching serial number. Preload remains consistent after delivery. No additional spacer processing or selection is required during assembly, enabling direct installation of complete sets. The ceramic rolling element solution perfectly fits long-duration ultra-high-speed finishing, alleviating spindle thermal elongation, restraining temperature rise and improving continuous machining stability.

The outer ring is plain standard design without integrated lubrication grooves, compatible with spindles adopting built-in housing oil channels. Open non-sealed structure cooperates with external oil-air lubrication system for continuous oil supply and cooling.

3 Core Performance Advantages

1. CD 15° small contact angle design: Excellent radial rigidity, low friction loss, optimized for maximum rotational speed under light to moderate axial loads.

2. HC silicon nitride hybrid ceramic ball structure: Lighter rolling elements cut centrifugal force at high speed, reduce raceway heat generation, lift limiting DN value and extend service life.

3. GA factory end-ground light preload DB duplex set: Uniform preload controlled by manufacturer, easy assembly without on-site spacer grinding, high consistency for mass production.

4. P4A enhanced super precision grade: Strict control over radial and axial runout, guaranteeing surface finish and dimensional stability during high-speed machining.

5. Open non-sealed construction: No seal friction loss, fully compatible with oil-air forced lubrication and circulating oil cooling lubrication systems.

5 Assembly Specifications & Usage Guidelines

5.1 Assembly Environment & Operation Standards

P4A super precision matched bearings must be assembled in constant-temperature dust-free clean workshops. Remove all burrs and metal debris on shaft and housing mating surfaces. Controlled thermal mounting method is recommended; open-flame heating is forbidden. Never strike bearing rings to avoid raceway indentations and damage to matching precision.

Important reminder: 7015 CDGA/HCP4A is factory permanent duplex matched set. Splitting two bearings for individual use or interchanging with same-model bearings from other batches is strictly prohibited. Once separated, end matching accuracy and preset preload cannot be recovered permanently.

5.2 Pairing & Preload Instructions

Supply condition: Duplex set of two bearings in DB back-to-back layout, GA light preload, marked with matching serial number.

Fixed mounting form: DB back-to-back fixed by factory assembly; conversion to DF/DT layout on site is impossible.

Selection tips:

Continuous ultra-high speed, strict temperature control, mass-production spindles, housing built-in oil channels → Prioritize 7015 CDGA/HCP4A;

Higher axial rigidity required, medium rotating speed with larger load → Select 25° contact angle ceramic ball duplex bearings;

Prototype development requiring flexible preload and layout adjustment → Choose single ceramic ball bearing 7015 CD/HC/P4A;

Medium speed range, limited budget, no extreme temperature control demand → Adopt all steel duplex set 7015 CDGA/P4A.

Selection reference:

① Single bearing, 15°, all steel balls →7015 CD/P4A

② Duplex DB light preload, 15°, all steel balls →7015 CDGA/P4A

③ Duplex DB light preload, 15°, HC ceramic balls →7015 CDGA/HCP4A(this model)

④ Duplex DB medium preload, 15°, HC ceramic balls →7015 CDGB/HCP4A

5.3 Lubrication Matching Scheme

No pre-filled grease. Oil-air forced circulation lubrication is preferred; circulating oil lubrication is also acceptable. Long-duration continuous high-speed grease lubrication is not recommended. High-precision filters must be installed in lubrication pipelines. Hard particles will easily scratch mirror raceways and ceramic rolling element surfaces. Mixing lubricants of different base oils or brands is forbidden. Ceramic rolling elements demand higher lubricant cleanliness than all steel bearings; filter elements should be replaced regularly to maintain clean lubrication medium.

5.4 Speed Parameter Note

HC silicon nitride ceramic balls effectively reduce high-speed centrifugal load and deliver far superior limiting DN performance compared with same-size all steel duplex bearings. This model is equipped with GA light preload, more suitable for continuous high-speed light-load finishing. Specifications with higher preload grade are recommended for heavy-duty impact working conditions. The complete machine must be equipped with efficient cooling system and sufficient speed safety margin. Open bearings have no built-in dust protection. Bearing housing must adopt reliable external sealing against dust and cutting fluid to prevent damage to rolling elements.

6 Daily Maintenance & Fault Troubleshooting

After full set assembly, perform multi-stage low-speed running-in, continuously monitor temperature rise and vibration data. Only raise rotating speed to rated working speed once all indicators stabilize. Track spindle temperature variation closely during running-in. Regularly inspect external housing sealing condition, lubrication pipeline pressure and flow rate to maintain stable continuous oil supply.

If persistent abnormal noise, rapid temperature rise or growing vibration occurs, check sequentially: lubricant cleanliness, assembly coaxial precision, excessive axial locking force, external impact load, cutting fluid or dust intrusion into bearing interior.

Typical failure modes of hybrid ceramic matched bearings include abrasive wear of raceways, surface spalling of ceramic rolling elements, local overheating caused by insufficient lubrication, edge loading from misalignment, preload overload due to over-tightening. Establish regular online monitoring of temperature and vibration to detect early damage and avoid unexpected spindle shutdown.