What is bearing steel and why is it used for wear-resistant precision parts?

Bearing steel (GCr15 in Chinese standard, equivalent to 52100/SUJ2/100Cr6) is a high-carbon chromium steel (C 0.95–1.05%, Cr 1.4–1.65%) specifically developed for rolling contact fatigue applications. After through-hardening and tempering, GCr15 achieves HRC 60–64 — the highest surface hardness achievable in standard steel without case carburising — combined with a fine, uniform carbide distribution that provides exceptional wear resistance. Compared to carburised alloy steel (20CrMnTi, HRC 58–62), GCr15 has superior through-hardness uniformity, better dimensional stability after heat treatment, and a harder martensitic matrix that resists micro-pitting under rolling contact. For non-bearing wear applications — guide shafts, pin shafts, bushings, and spindle parts — GCr15 is specified because its through-hardness and dimensional stability after heat treatment allow tighter tolerances to be maintained in service.

What tolerances can you achieve on hardened bearing steel parts?

OD tolerances on ground bearing steel parts: h5 (±0.003–0.005mm) for precision guide shafts and spindle parts; h6 (±0.005–0.008mm) for standard shafts and roller shafts. Bore tolerances: H6 for precision bushings and bearing ring bores; H7 for general bore fits. Cylindricity: ≤0.001mm for precision spindle parts; ≤0.002mm for pin shafts; ≤0.003mm for roller shafts and guide shafts. Roundness: ≤0.001mm for spindle noses. Surface finish: Ra ≤0.05μm for bearing raceway surfaces (superfinished); Ra ≤0.1μm for guide shaft ODs; Ra ≤0.2μm for roller shaft ODs standard. All tolerances are held after heat treatment — ground on precision cylindrical grinders after hardening, not before.

What is the heat treatment process for GCr15 bearing steel parts?

GCr15 bearing steel is through-hardened by austenitising at 840–860°C followed by oil quench and low-temperature tempering at 150–180°C. This achieves surface and core hardness HRC 60–64 — uniform throughout the cross-section, not just a surface case. The low-temperature temper maintains maximum hardness while relieving quench stress that would cause dimensional instability in service. For parts requiring dimensional stability over time (precision spindle parts, guide shafts used in measurement equipment), cryogenic treatment (-80°C to -196°C) after quench is available — this converts retained austenite to martensite, reducing long-term dimensional drift to <1μm over 10 years. Heat treatment record (process parameters, hardness test per piece) is included with every hardened part order.

What surface finishing operations do you perform after hardening?

After hardening, bearing steel parts are finish-ground on precision cylindrical grinders (OD grinding) or internal grinders (bore grinding). Cylindrical OD grinding achieves Ra ≤0.2μm and cylindricity ≤0.003mm as standard. For raceway surfaces, bearing ring bores, and precision spindle surfaces, superfinishing (honing or lapping) follows grinding to achieve Ra ≤0.05μm. Superfinishing removes grinding marks and grinding-induced residual tensile stress from the surface layer — critical for rolling contact fatigue life, which is directly related to surface roughness and stress state. For precision guide shafts requiring Ra ≤0.1μm, plunge grinding and spark-out cycle achieves this without separate superfinishing.

What is the difference between a guide shaft and a plain shaft?

A precision guide shaft (精密导向轴) is a hardened and ground shaft specifically optimised for linear bearing and ball bushing guidance — tight OD tolerance h5 (±0.003–0.005mm), cylindricity ≤0.003mm, straightness ≤0.01mm/m, and Ra ≤0.1μm surface finish. These specifications are required for the linear bearing inner diameter to maintain consistent radial clearance along the full shaft length. A plain shaft (光轴) is a smooth cylindrical shaft for general support and rotation — typically h6 OD tolerance, Ra ≤0.4μm, without the cylindricity and straightness specifications that a guide shaft requires. For linear motion applications with recirculating ball bushings or needle roller bushings, a precision guide shaft is required — substituting a plain shaft typically results in bearing premature failure or excessive play.

What surface treatments are available for bearing steel parts?

For hardened GCr15 parts, surface treatment options are limited by the need to preserve dimensional accuracy and surface finish: hard chrome plating (10–30μm, HV 900–1200) is the standard wear enhancement for pin shafts and roller shafts — applied after grinding, then re-ground to final OD dimension; electroless nickel plating (3–5μm thin) for corrosion protection without significant dimensional change — suitable for guide shafts in humid or chemical environments; black oxide for very mild corrosion protection with zero dimensional change (< 0.5μm) — preserves all ground tolerances; and PVD TiN or TiAlN coating (2–4μm) for maximum surface hardness (HV 2300+) and reduced friction on guide shaft surfaces. Oil protection packaging is standard for all hardened parts during transit.

What is MOQ and lead time for bearing steel precision parts?

Minimum order quantity is 1 piece for custom precision parts. For small standard sizes (guide shafts, pin shafts below Ø20mm), production economics are better at 10+ pieces due to grinding setup time. Standard lead time: simple turned and hardened parts (pin shafts, roller shafts) without secondary operations: 7–12 working days (includes heat treatment time). Precision-ground guide shafts and bearing rings: 10–15 working days. Superfinished spindle parts and bearing ring raceways: 12–20 working days. For production quantities of 50+ pieces, lead times are quoted individually. We confirm exact lead time in every quotation.

Product Category

BRS — 001 to 012

Bearing Steel
Precision
Wear Parts

12 product lines machined from GCr15 bearing steel (52100/SUJ2/100Cr6) — bearing rings, roller shafts, guide shafts, needle roller guides, pin shafts, spindle parts, guide wheels, wear bushings, and linear motion components. HRC 60–64. Ground to h5/H6. Raceway Ra ≤0.05 μm.

Rockwell Hardness Scale — GCr15 Parts vs Common Grades

Q235
HRB85

45# N
HRC20

42CrMo
HRC32

40Cr
HRC42

GCr15
HRC60

GCr15
HRC64 ▶

SoftMediumHardVery HardBearing Grade

GCr15 through-hardened to HRC 60–64 — the standard for rolling contact wear applications

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GCr15 Bearing Steel Precision Parts Roller Shaft Guide

HRC 64

Max Hardness

Bearing Ring Spindle Wear Bushing Ground Superfinish

Ra 0.05μm

Raceway SF

Product Lines

HRC 60–64

GCr15 Hardness

h5 / H6

Ground Tolerance

Ra ≤0.05^μm

Raceway SF

24^hr

Quote Turnaround

Bearing Rings ✦ Roller Shafts ✦ Needle Roller Guide Parts ✦ Wear-Resistant Pin Shafts ✦ Precision Spindle Parts ✦ Guide Wheels ✦ High-Hardness Shaft Parts ✦ Wear-Resistant Bushings ✦ Precision Guide Shafts ✦ Linear Motion Parts ✦ Rolling Mechanism Parts ✦ Mechanical Wear Parts ✦ Bearing Rings ✦ Roller Shafts ✦ Needle Roller Guide Parts ✦ Wear-Resistant Pin Shafts ✦ Precision Spindle Parts ✦ Guide Wheels ✦ High-Hardness Shaft Parts ✦ Wear-Resistant Bushings ✦ Precision Guide Shafts ✦ Linear Motion Parts ✦ Rolling Mechanism Parts ✦ Mechanical Wear Parts ✦

Full Product Range

12 Bearing Steel
Precision Wear Product Lines

Select a category tab · GCr15 / 52100 / SUJ2 · HRC 60–64 · Ground post-hardening · MOQ 1 piece

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Product Categories

Four hardened and ground shaft product lines in GCr15 bearing steel — roller shafts, wear-resistant pin shafts, high-hardness shaft parts, and precision guide shafts. All OD ground after hardening to h5/h6 tolerance. Cylindricity ≤0.002–0.003 mm. Surface finish Ra ≤0.1–0.2 μm standard; Ra ≤0.05 μm lapped on precision spindle and guide applications.

Precision Guide Shaft GCr15 Hard Chrome h5 Cylindricity Linear Bearing

BRS-009

SHAFTS / 009 — FEATURED

Precision Guide Shafts

Hardened and ground precision linear guide shafts for recirculating ball bushings (linear bearings), needle roller bushings, and plain bush linear guides. GCr15 through-hardened HRC 60–64; OD tolerance h5 (±0.003–0.005 mm on nominal diameter); cylindricity ≤0.003 mm across the full shaft length — the critical specification because linear bearing inner diameter maintains radial clearance along the shaft, and any cylindricity deviation produces localized contact stress and bearing noise. Straightness ≤0.01 mm/m; Ra ≤0.1 μm standard, Ra ≤0.05 μm lapped for highest-precision linear stages. Hard chrome plating option (15–25 μm, HV 1000+) for maximum wear life on high-cycle, high-speed linear axes — chrome-plated guide shafts then re-ground to OD dimension after plating. Chamfered ends and centre-drilled for steady-rest during grinding. Diameter range Ø4–Ø80 mm standard; larger on request.

h5 OD · ≤0.003mm cyl. Ra ≤0.1μm Straight ≤0.01/m Hard chrome option

GCr15 · SUJ2 · 100Cr6 Get Quote

Roller Shaft GCr15 HRC 60-64 h6 Ground Ra ≤0.2μm

BRS-002

SHAFTS / 002

Roller Shafts

Hardened and ground roller shafts and cam follower shafts. GCr15 HRC 60–64; OD h6; cylindricity ≤0.003 mm; Ra ≤0.2 μm. Chamfered or radiused ends. Used for conveyor rollers, cam followers, and rolling element support shafts where journal hardness must match the rolling element hardness.

h6 · HRC 60–64Ra ≤0.2μm

GCr15 · 40Cr HTGet Quote

Wear-Resistant Pin Shaft GCr15 Hardened h6 Cylindricity

BRS-004

SHAFTS / 004

Wear-Resistant Pin Shafts

Hardened pin shafts and pivot pins for high-cycle articulation joints. GCr15 HRC 60–64; OD h6; cylindricity ≤0.002 mm. Ra ≤0.2 μm standard. Hard chrome plating option for additional corrosion and wear resistance. Chamfered leading end; retaining groove option.

h6 · Cyl. ≤0.002mm

GCr15 · SUJ2Get Quote

High-Hardness Shaft Part GCr15 Cr12MoV HRC 60-64 Press Tool

BRS-007

SHAFTS / 007

High-Hardness Shaft Parts

General-purpose high-hardness shaft and rod parts in GCr15 or Cr12MoV. HRC 60–64; OD h6; cylindricity ≤0.003 mm. Used in press tooling, cold forming dies, and machine elements where maximum hardness and wear resistance are required.

HRC 60–64Cr12MoV option

GCr15 · Cr12MoV · D2Get Quote

Materials: GCr15 · SUJ2 · 100Cr6 · 40Cr (HT) · Cr12MoV · D2

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Bearing ring blanks and finish-ground bearing rings in GCr15, and ultra-high-precision spindle bodies for machine tool and instrument applications. Bearing ring raceway superfinished to Ra ≤0.05 μm. Spindle OD h4/h5; roundness ≤0.001 mm. All bearing rings supplied with concentricity report. Spindle parts with dimensional stability option (cryogenic treatment) for long-term positional accuracy.

GCr15 Bearing Ring Ground Superfinish Raceway OD ID Concentricity

BRS-001

BEARING / 001 — FEATURED

Bearing Rings

GCr15 bearing ring inner and outer race blanks and finish-ground rings for custom and non-standard bearing sizes. Supplied in two states: (A) rough-turned + hardened HRC 60–64, ready for customer cylindrical and ID grinding — all surfaces with ±0.3 mm grinding allowance; (B) finish-ground — OD h5, bore H6, face parallelism ±0.005 mm, OD/bore concentricity ≤0.003 mm, raceway profile ground to ±0.005 mm. Raceway superfinishing to Ra ≤0.05 μm available — this removes grinding-induced surface tensile stress and marks that initiate subsurface fatigue cracks under rolling contact loading. Cryogenic treatment (-80°C) after hardening available for maximum dimensional stability. Hardness test per piece included.

OD h5 · Bore H6 Concentric ≤0.003mm Ra ≤0.05μm SF Cryogenic option

GCr15 · SUJ2 · 100Cr6 Get Quote

Precision Spindle Part GCr15 h4 Roundness Superfinish Machine Tool

BRS-005

BEARING / 005

Precision Spindle Parts

High-precision spindle bodies for machine tool spindles, measuring instruments, and precision rotary stages. GCr15 HRC 60–64; OD h4/h5; roundness ≤0.001 mm; Ra ≤0.05 μm (superfinished). Cryogenic treatment for long-term dimensional stability. CMM roundness and cylindricity report included.

h4/h5 ODRoundness ≤0.001mm

GCr15 · SUJ2Get Quote

Custom Bearing Ring Non-Standard Size GCr15 Ground CNC

BRS-001B

BEARING / 001B

Custom Non-Standard Bearing Rings

Non-standard bearing rings for obsolete, large-diameter, and application-specific bearings unavailable from catalogue sources. Custom OD, bore, and width to drawing. GCr15 finish-ground in the same operations as standard bearing rings. MOQ 1 piece.

Non-standard sizeMOQ 1 piece

GCr15 · SUJ2Get Quote

Materials: GCr15 · SUJ2 · 100Cr6 / 52100

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Guide wheels and track rollers for linear profiled rail and circular track guidance applications, and needle roller guide cage parts for needle bearing linear and rotary assemblies. Guide wheel OD profile ground to ±0.005 mm; bore H6; GCr15 HRC 60–64. Needle guide rail profile ground to ±0.005 mm; surface Ra ≤0.1 μm for consistent needle contact.

BRS-006

GUIDES / 006 — FEATURED

Guide Wheels & Track Rollers

Hardened GCr15 guide wheels and track rollers for V-groove, flat track, and profiled rail linear and rotary guidance systems. OD profile ground to ±0.005 mm — profile tolerance directly determines tracking accuracy. Bore H6 for mounting on shaft; OD/bore concentricity ≤0.003 mm for uniform radial runout during rolling contact. Ra ≤0.2 μm on OD contact face. Two-flange, single-flange, and flat OD profiles available. Custom V-groove angle, flange diameter, and contact width to drawing. Applications: linear gantry guide rollers, cam track rollers, conveyor guide wheels, and automated storage/retrieval system carriage wheels. Hard chrome OD option for maximum rolling surface wear life.

OD profile ±0.005mm Bore H6 Concentric ≤0.003mm Custom profile

GCr15 · SUJ2 · Cr12MoV Get Quote

BRS-003

GUIDES / 003

Needle Roller Guide Parts

Precision needle roller cage guides and linear needle rail guides. GCr15 HRC 60–64; needle contact surface Ra ≤0.1 μm; profile tolerance ±0.005 mm. Used in flat-cage linear needle bearing assemblies and custom needle roller retainer guides where standard cage sizes are unavailable.

Ra ≤0.1μmCustom profile

GCr15 · SUJ2Get Quote

Custom Cam Track Roller Guide Profiled GCr15 CNC Ground

BRS-006B

GUIDES / 006B

Custom Cam & Track Rollers

Custom cam follower roller bodies and profiled track rollers with non-standard OD profile geometry (crowned, gothic arch, or custom curve). Profile ground to ±0.005 mm by CNC profile grinding. GCr15 HRC 60–64. Bore H6; stud thread option for stud-type cam followers.

Custom OD profileStud type

GCr15 · Cr12MoVGet Quote

Materials: GCr15 · SUJ2 · 100Cr6 · Cr12MoV

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Wear-resistant bushings, linear motion housing parts, rolling mechanism components, and custom mechanical wear-resistant parts in GCr15 and tool steel. Bushing OD/ID concentricity ≤0.003 mm; H6 bore ground after hardening. Linear motion housing bore H6; surface hardness HRC 58–64. All parts with dimensional report and hardness test record.

Wear-Resistant Bushing GCr15 HRC 60-64 OD/ID Concentricity H6 Bore Ground

BRS-008

BUSHINGS & LINEAR / 008 — FEATURED

Wear-Resistant Bushings

Hardened GCr15 bearing steel bushings for high-load, high-cycle applications where bronze or standard steel bushings have insufficient wear life. Through-hardened HRC 60–64 after rough turning; bore and OD ground after hardening to remove heat-treatment distortion. OD/ID concentricity ≤0.003 mm — ensures even wall thickness and uniform load distribution across the bushing bore, preventing localised stress concentration. Bore H6 ground to Ra ≤0.2 μm; OD k6 for interference fit into housing. Oil groove and lubrication hole options — machined before hardening at pre-agreed locations. Flange bushing versions. Applications: press tool guide bushings, injection mould guide elements, cam follower bushings, chain sprocket bushings, and articulation joint bushings in high-load machines. Supplied with CMM concentricity report and hardness test certificate.

OD/ID ≤0.003mm HRC 60–64 H6 bore · k6 OD CMM + hardness cert

GCr15 · SUJ2 · Cr12MoV Get Quote

Materials: GCr15 · SUJ2 · 100Cr6 · Cr12MoV · D2 Tool Steel

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Manufacturing Capability

What Bearing Steel Parts Require
Beyond Standard Hardening and Turning

💎

Superfinishing — Ra ≤0.05 μm After Grinding

Raceway surfaces and precision spindle ODs superfinished to Ra ≤0.05 μm — 8× better than ground Ra ≤0.4 μm. Superfinishing removes grinding marks and surface tensile stress that initiate rolling contact fatigue cracks. For bearing rings, this directly extends raceway fatigue life under rolling contact loading.

Ra ≤0.05μmRacewaysSpindle parts

❄

Cryogenic Treatment — Long-Term Stability

Cryogenic treatment (-80°C to -196°C) after quench converts retained austenite to martensite — reduces long-term dimensional drift to <1 μm over years. For precision guide shafts and spindle parts in measurement equipment or machine tools where dimensional stability over time is a specification, not an assumption.

-196°C treatment<1μm driftSpindle / guide

⚙

Ground Post-Hardening — h5/H6 Maintained

All GCr15 parts ground after hardening — not before. Hardening distorts dimensions by 0.05–0.2 mm. Pre-hardening grinding produces a part that meets tolerance before hardening but not after. Post-hardening cylindrical grinding restores OD h5/h6 and bore H6 to specification after distortion is eliminated.

Post-HT grindh5 / H6Cylindricity ≤0.003mm

📊

Hardness — 100% Per-Piece Test on All Parts

Every hardened bearing steel part hardness-tested on Rockwell tester before delivery. HRC 60–64 verified per piece — not sampled per batch. A batch average of HRC 62 could include individual parts at HRC 57 (too soft) that a sampling plan would miss. Per-piece testing is the only way to guarantee specification.

100% per pieceHRC 60–64Reported per order

◎

Concentricity ≤0.003 mm — OD to Bore

Bearing ring and bushing OD/bore concentricity ≤0.003 mm — measured by CMM after grinding. For a bearing ring, OD/bore concentricity determines raceway-to-housing eccentricity, which loads the rolling elements non-uniformly and reduces bearing life. Not assumed from grinding setup — measured and reported.

≤0.003mmCMM measuredPer piece report

📐

Guide Shaft Cylindricity — Full Length

Guide shaft cylindricity ≤0.003 mm measured over the full shaft length — not just at the ends. A shaft that is h5 at both ends but bends or tapers in the middle generates variable radial clearance in the linear bearing and causes binding at the deviation location. We measure and report cylindricity across multiple sections.

Full-length measure≤0.003mmMulti-section

Precision Specifications

Tolerances & Hardness Reference — Bearing Steel Parts

📐

Tolerances by Feature

Guide Shaft OD

h5 / ±0.003mm

Shaft OD Std

h6 / ±0.006mm

Bore (Bushing)

Spindle OD

h4 / ±0.002mm

OD/Bore Concentric

≤0.003 mm

Cylindricity

≤0.003 mm

Roundness (Spindle)

≤0.001 mm

Surface (Raceway SF)

Ra ≤0.05 μm

🔩

Hardness & Material Reference

GCr15 Hardness

HRC 60–64

Through-hardened. Uniform core and surface. Standard bearing steel specification.

Cr12MoV Hardness

HRC 60–62

High-carbon chromium tool steel. Higher carbon than GCr15. For die and heavy-wear parts.

Raceway Ra

≤0.05^μm

Superfinished bearing ring raceway. Removes grinding stress layer. Extended fatigue life.

Guide Shaft Ra

≤0.1^μm

Precision guide shaft OD. Standard for recirculating ball bushing linear guidance.

Cryogenic

-196°C

Optional post-quench treatment. Converts retained austenite. <1μm long-term drift.

Hardness Test

100%

Every piece tested. HRC per piece report. Not sampled — verified.

Material Selection

Bearing Steel Grades for Precision Wear Parts

Bearing steel grade selection is driven by hardness uniformity, dimensional stability after heat treatment, and rolling contact fatigue life.

MAT / 01

GCr15 (52100 / SUJ2 / 100Cr6)

HRC 60–64 · C 0.95–1.05% · Cr 1.4–1.65%

The universal bearing steel for all bearing rings, guide shafts, roller shafts, and wear bushings. Best rolling contact fatigue life. Through-hardened uniformly to HRC 60–64. Excellent dimensional stability after proper heat treatment and cryogenic treatment.

All Bearing PartsStandard grade

MAT / 02

Cr12MoV (D2 equivalent)

HRC 60–62 · High carbon-chromium tool steel

For wear-resistant bushings, custom wear parts, and cam guide parts requiring higher carbide volume fraction than GCr15. Better wear resistance than GCr15 in sliding wear applications. Standard for die guide bushings, injection mould guide elements, and heavy-duty wear liners.

Wear BushingsDie Guides

MAT / 03

SUJ2 / 100Cr6 / AISI 52100

International equivalents to GCr15 · Same specification

International equivalent grades — SUJ2 (JIS, Japan), 100Cr6 (EN, Europe), 52100 (AISI, USA) — all meet the same chemical composition and performance specification as GCr15. We can source and certify any of these grades for export orders requiring specific country standards. Mill certificate with grade designation per customer requirement.

Export ordersAny standard

MAT / 04

D2 Tool Steel (Cr12)

HRC 58–62 · Best sliding wear resistance

Best sliding and abrasive wear resistance of common tool steels due to high vanadium carbide content. Used for custom wear liners, punch and die elements, and machine wear parts where abrasive wear (rather than rolling contact fatigue) is the primary failure mechanism.

Abrasive wearWear liners

MAT / 05

M2 HSS (High Speed Steel)

HRC 62–65 · Best hot hardness

< div class="dc">For custom wear parts and spindle elements requiring hardness retention at elevated operating temperatures (above 200°C) where GCr15 softens. Also used for spindle nose parts in high-speed cutting applications. HRC 62–65 achievable. Harder to machine than GCr15 — all features ground after hardening.< div class="tgs">High temp wearSpindle noses

Surface Treatments

Surface Finishing for Bearing Steel Precision Parts

Surface treatment for hardened bearing steel parts must preserve dimensional tolerance achieved by precision grinding — most coatings require tolerance allowance at DFM stage.

✦

Hard Chrome Plating

10–30 μm, HV 1000–1200. Applied after grinding, then re-ground to OD final dimension. Standard for guide shafts and roller shafts requiring maximum OD wear resistance and corrosion resistance. Chrome plating tolerance must be specified — plating thickness is controlled and allowance provided in pre-plate grinding.

Guide ShaftsRoller Shafts

🔲

Black Oxide

Zero dimensional change (<0.5 μm). Mild corrosion protection and rust prevention for oil-lubricated bearing steel parts. Applied after precision grinding — preserves all h5/h6 tolerances. Standard storage and transit treatment for ground bearing steel parts before assembly.

All ground partsTransit protection

💧

Electroless Nickel (3–5 μm)

Thin EN (3–5 μm) for corrosion protection of guide shafts and roller shafts in humid and chemical environments where hard chrome is over-specified. Tight dimensional control — thickness specified and confirmed at DFM. Applied after precision grinding; re-measured post-plating.

Humid env.Chemical contact

🌟

PVD TiN / TiAlN (2–4 μm)

Physical vapour deposition TiN (gold, HV 2300) or TiAlN (grey, HV 3500) coating. Near-zero dimensional change (2–4 μm per surface). Maximum surface hardness for guide shaft ODs in abrasive particle environments — coating is harder than the hard chrome it replaces without the thermal stress of chrome plating.

Abrasive env.PVD coated

❄

Oil Protection Packaging

All ground bearing steel parts packed with corrosion-inhibitor oil and individually wrapped in VCI (volatile corrosion inhibitor) film. Protects superfinished and ground surfaces during transit and storage. Ground Ra ≤0.05 μm surfaces are particularly susceptible to rust during transit if unprotected — we never ship unprotected hardened ground parts.

All ground partsStandard

💎

Superfinish (Ra ≤0.05 μm)

Not a coating — a surface finishing operation. Honing or vibratory superfinishing after cylindrical grinding to Ra ≤0.05 μm. Removes grinding marks and surface tensile residual stress. Standard for bearing ring raceways and precision spindle ODs. Extends rolling contact fatigue life significantly compared to ground-only surfaces.

RacewaysSpindle OD

Production Workflow

From Drawing to Superfinished, Certified Bearing Steel Part

DFM Review

Grade, HT process, grinding allowance, cryogenic spec, and superfinish scope confirmed. 24hr response.

Material

GCr15 billet or bar receipted with mill certificate. Chemical composition per heat number verified.

Rough Turning

Rough turned to ±0.3mm grinding allowance on all surfaces. Raceway profiles pre-turned.

Hardening & Cryo

Through-harden HRC 60–64. Cryogenic treatment (-196°C) if specified. Per-piece hardness test recorded.

Precision Grinding

OD cylindrical + bore ID grinding post-HT. Raceway superfinish to Ra ≤0.05μm where specified.

CMM & Delivery

CMM concentricity + cylindricity report. Per-piece HRC record. VCI oil pack. Mill cert enclosed.

Our Advantage

Why Precision Engineers Specify Our Bearing Steel Parts

Superfinish Ra ≤0.05μm — Raceway Grade

Bearing ring raceways and spindle ODs superfinished to Ra ≤0.05 μm — bearing-manufacturer surface quality. Grinding marks that remain at Ra ≤0.4 μm initiate subsurface fatigue cracks under rolling contact loading. We remove them. The difference between a bearing ring that lasts 10 million cycles and one that fails at 1 million.

100%

Hardness Per Piece — Every Single Part

Every hardened bearing steel part Rockwell-tested before delivery. HRC 60–64 verified per piece — not sampled per batch. A batch with one under-hardened part at HRC 55 is a field failure. Per-piece testing eliminates this risk. HRC recorded and reported per part number.

POST

Ground After Hardening — Not Before

All OD and bore features precision-ground after hardening and cryogenic treatment. Hardening distorts by 0.05–0.2 mm. Pre-hardening grinding is meaningless for a precision part. Post-hardening grinding restores h5/H6 tolerance after distortion is complete and will not recur.

❄

Cryogenic Treatment — Dimensional Stability

Cryogenic treatment available for precision guide shafts and spindle parts where long-term positional stability matters. Converts retained austenite to martensite. Reduces dimensional drift to <1 μm over years. Not offered as a premium — offered as the solution to retained austenite instability that most suppliers ignore.

Frequently Asked Questions

Bearing Steel Precision Parts — Common Questions

Technical questions about bearing steel grades, tolerances, superfinishing, and the hardening process for precision wear parts.

GCr15 (52100/SUJ2/100Cr6) is a high-carbon chromium steel (C ~1%, Cr ~1.5%) through-hardened to HRC 60–64 — the highest hardness achievable in standard steel without surface carburising. The uniform fine carbide distribution provides exceptional rolling contact fatigue resistance and wear resistance. vs carburised alloy steel (20CrMnTi, HRC 58–62): GCr15 has superior through-hardness uniformity, better dimensional stability, and a harder martensitic matrix — which is why all bearing manufacturers use it for ring and rolling element production.

OD: h4 (±0.002mm) for spindle parts; h5 (±0.003–0.005mm) for guide shafts; h6 for roller shafts. Bore: H6 for bushings and bearing rings. Cylindricity: ≤0.001mm for spindle parts; ≤0.003mm for guide shafts and roller shafts. OD/bore concentricity: ≤0.003mm. Surface finish: Ra ≤0.05μm superfinished raceways; Ra ≤0.1μm guide shafts; Ra ≤0.2μm standard ground. All tolerances held after hardening — ground post-HT.

GCr15 is through-hardened by austenitising at 840–860°C then oil-quenched to achieve uniform HRC 60–64 through the cross-section. Low-temperature tempering at 150–180°C relieves quench stress while maintaining hardness. Cryogenic treatment (-80°C to -196°C) after quench converts retained austenite to martensite — important for dimensional stability in precision guide shafts and spindle parts. Heat treatment record (process parameters + hardness test per piece) included with every order.

Cylindrical grinding produces Ra ≤0.4 μm but leaves surface tensile residual stress and micro-grinding marks. Under rolling contact loading, these are the initiation sites for subsurface fatigue cracks that propagate and cause spalling. Superfinishing (honing or vibratory finishing to Ra ≤0.05 μm) removes the stressed surface layer and marks — dramatically extending rolling contact fatigue life. For bearing rings that will see 10+ million contact cycles, the difference between ground-only and superfinished raceway life can exceed 3×.

Yes — two supply states: (A) Rough-turned + hardened HRC 60–64 with ±0.3mm grinding allowance on all surfaces — ready for your grinding operations; (B) Finish-ground to OD h5, bore H6, concentricity ≤0.003mm, raceway profile ±0.005mm, with optional superfinish to Ra ≤0.05μm. Custom non-standard bearing ring sizes available with MOQ 1 piece. Mill certificate and hardness test report standard on all bearing ring orders.

A precision guide shaft (精密导向轴): OD h5, cylindricity ≤0.003mm across full length, straightness ≤0.01mm/m, Ra ≤0.1μm — all ground post-HT GCr15 HRC 60–64. Required for recirculating ball bushing linear bearing guidance. A plain shaft (光轴): typically h6 OD, Ra ≤0.4μm, without tight cylindricity or straightness specs. Substituting a plain shaft for a guide shaft in a linear bearing application typically causes variable radial clearance, bearing noise, and premature failure at the points where cylindricity deviation concentrates contact stress.

For hardened GCr15 (dimensional preservation priority): Black oxide — <0.5μm change, mild protection, preserves all ground tolerances, standard transit protection; Hard chrome — 10–30μm, HV 1000+, applied post-grind then re-ground to OD final dimension, for guide shafts and roller shafts requiring maximum wear life; Thin EN — 3–5μm electroless nickel, corrosion protection for humid environments; PVD TiN/TiAlN — 2–4μm, HV 2300–3500, abrasive environment coating. All coatings with thickness specified and post-plate dimension verified.

MOQ: 1 piece for custom sizes. Standard lead times: simple hardened and ground parts (pin shafts, roller shafts): 7–12 working days (includes heat treatment time). Precision-ground guide shafts and bearing rings: 10–15 working days. Superfinished spindle parts and bearing ring raceways: 12–20 working days. Production quantities 50+ pieces: quoted individually. Exact lead time confirmed in every quotation.

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Every enquiry includes a DFM review — tolerance feasibility, material confirmation, and process approach confirmed before production starts. MOQ 1 piece.

24hr

Quote Response

MOQ 1

Prototypes OK

ISO

9001:2015

📐

DFM Review on Every Enquiry

Tolerance feasibility, fixturing strategy, and material confirmation. Specific, actionable feedback — not generic pushback.

🎯

First Article Inspection — Standard

FAI report on every new run. Material certs and surface treatment certs included with every shipment.

🔄

Same Process: Prototype to Production

Process plan from your prototype applies to production batches. No re-qualification when you scale.

⚙

3 / 4 / 5-Axis CNC + Turning

Complex structural parts, shafts, housings, and transmission components. Metals and engineering plastics.

ISO 9001:2015 3/4/5-Axis Milling CNC Turning CMM Inspection Global Delivery

Name

Company

Material

Surface Finish

Additional Requirements

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Bearing SteelPrecisionWear Parts

12 Bearing SteelPrecision Wear Product Lines

What Bearing Steel Parts RequireBeyond Standard Hardening and Turning

Tolerances & Hardness Reference — Bearing Steel Parts

Bearing Steel Grades for Precision Wear Parts

Surface Finishing for Bearing Steel Precision Parts

From Drawing to Superfinished, Certified Bearing Steel Part

Why Precision Engineers Specify Our Bearing Steel Parts

Bearing Steel Precision Parts — Common Questions

Send Your Drawing.Get a Quote.

Bearing Steel
Precision
Wear Parts

12 Bearing Steel
Precision Wear Product Lines

What Bearing Steel Parts Require
Beyond Standard Hardening and Turning

Send Your Drawing.
Get a Quote.