Angular contact ball bearings — also called radial-thrust ball bearings — carry combined radial and axial loads through a nominal contact angle (α) between the ball-race contact line and the radial plane; LYC lists contact angle as the governing variable for axial capacity [S2].
Single-row units are the workhorse for machine-tool spindles, gearboxes, reducers and superchargers, and are virtually always installed in a back-to-back (DB), face-to-face (DF) or tandem (DT) pair rather than as a single bearing [S2]. Two-row axial angular contact variants from suppliers such as HIWIN are flanged or unflanged and are engineered specifically to mount ballscrews against a linear guide bearing seat [S3].
Contact Angle, Load Direction and the α-Series Trade-Off
Common nominal contact angles in production catalogues are 15° (C suffix in ISO 15:2017 nomenclature), 25° (AC) and 40° (B) — a larger α raises axial load capacity and axial rigidity but lowers the limiting speed and increases the radial-equivalent load factor, so high-speed spindles almost always pick 15° while heavy-axial machine tools pick 40° [S2].
For pure thrust applications where a crossed-roller guide would be too slow or too large, four-point contact geometries (e.g. QJ series) provide a single-row package that handles axial load in both directions, but at a lower radial capacity than a matched pair of single-row units at the same bore [S2]. HIWIN markets two-row axial angular contact ball bearings with and without a flanged outer ring to handle the bidirectional thrust from a preloaded ballscrew nut [S3].
Duplex Mounting, Preload and the DB/DF/DT Decision
Single-row angular contact bearings can only transmit axial load in one direction, so they are almost always supplied as a matched pair — DB (back-to-back) for moment rigidity and shaft expansion, DF (face-to-face) for shorter shaft spans and lower moment stiffness, or DT (tandem) for pure one-direction thrust paired with a third bearing for the opposite direction [S2].
Preload class (light, medium, heavy) is the next decision: LYC warns that any angular misalignment between inner and outer rings in a preloaded pair is amplified — balls and cage take additional load and bearing life drops — so paired sets demand tighter mounting tolerances than standalone deep-groove ball bearings [S2]. Solid Bearings lists the 7234 B/DF (170×310×104 mm) as a back-to-back machine-tool main-spindle configuration, illustrating the DB convention for heavy radial + axial spindle duty [S5].
Bore Series, Boundary Dimensions and Standard Stock
ISO 15 dimension series drive bore/diameter/width — 719 (extra-light), 70 (light), 72 (medium), 73 (heavy) — and a typical 70xx stock part on Made-in-China lists a 1000-piece minimum order with claimed 500,000-piece monthly supply, which is the volume tier for commodity Chinese supply [S4].
7019 (95 mm bore, 145 mm OD) is a common spindle size and is widely stocked as both single-row and matched-pair sets in 2026 wholesale catalogues [S4]. For larger spindle main shafts the 7234 B/DF at 170×310×104 mm is a published back-to-back unit, with the old designation 366234 carried for cross-reference to legacy papers [S5]. Buyers sourcing from wholesale portals can expect price ranges starting near US$1.00 per piece for low-precision automotive-grade SUV angular contact bearings and scaling up with tolerance, material and ABEC class [S1].
Limiting speed is the headline reason a 15° C-series contact angle is chosen over a 40° B-series for high-speed spindles; LYC publishes both oil and grease limiting-speed columns in their product finder, and the grease figure is typically 60–70% of the oil figure for the same bearing [S2].
HIWIN's two-row axial angular contact units are typically grease-packed for the life of the ballscrew assembly because they sit in a sealed bearing seat; field re-lubrication paths are integrated as grease nipples and lubrication adapters in the surrounding linear-axis accessory line [S3].
Material, Cage and Application Fit
Standard materials are through-hardened chromium steel (AISI 52100 / 100Cr6) rings plus steel balls, with brass, pressed steel or PEEK/phenolic cages selected for the temperature and noise envelope; precision grades ABEC-3 (P6) through ABEC-7 (P4) are commonly offered, and machine-tool main spindles usually require P4 or better paired with controlled-cleanliness assembly [S2][S5].
Application fit is straightforward: machine-tool main spindles and ballscrews pair angular contact units with a linear guide for axial support; gearboxes and reducers use matched sets in DB configuration to react combined gear-mesh loads; superchargers and pumps use single-row or paired sets where one direction of thrust dominates. The class of single-row deep-groove angular-contact-bearing is NOT a drop-in for a thrust-only needle or crossed-roller bearing when the axial-to-radial ratio is very high — use a dedicated thrust or crossed-roller assembly instead.
Sourcing on B2B Portals in 2026
Chinese B2B portals continue to dominate generic angular contact supply: Made-in-China lists hundreds of 70xx and 72xx SKUs with FOB pricing tiers starting near US$1/piece for non-precision auto-grade units and scaling into the US$10–US$20 range for precision spindle units, with TT or LC payment terms and Shanghai as a common loading port [S1][S4]. Okorder lists a 7019 product with a 1000-piece MOQ and 500,000-piece monthly supply capability — the volume tier for OEM-sized buyers [S4]. Solid Bearings is one of many small-stockists carrying 7234 B/DF matched pairs at 170×310×104 mm for spindle rebuilds [S5].
For a related comparison on how a ballscrew-driven axis is mounted against a linear-motion system, the Metal Stamping Part Selection guide walks through the spec-first sourcing discipline that pairs cleanly with bearing selection. Process engineers sourcing complete motion packages typically follow a similar spec-first sheet — contact angle, bore, tolerance class, lubrication and pairing — when comparing ball bearing SKUs across portals.
Selection Checklist Before Issuing the PO
Confirm five values before ordering: (1) bore and OD from the ISO 15 dimension series; (2) contact angle — 15° / 25° / 40° — matched to the load/speed trade; (3) tolerance class — P0/P6/P5/P4/P2 — matched to spindle precision; (4) duplex configuration — DB / DF / DT / QJ — matched to load direction and moment; (5) cage and lubrication — grease-packed sealed for ballscrew seats, oil-mist for high-speed spindles [S2][S3].
Verify the supplier publishes dynamic (Cr) and static (Cor) load ratings, oil and grease limiting speeds, and matches ISO 15 boundary dimensions; if a 7019 single-row is quoted at the same price as a matched 7019 DB pair, the latter should be a 2-piece set and the supplier should confirm matched bore and preload class on the certificate [S2][S4].