Single-row tapered roller bearings remain the dominant industrial configuration, with metric 30000-series examples such as the 32007 (35 × 62 × 18 mm, 2.0 kg) [S6] and 30244 (220 × 400 × 73 mm) [S8] covering the bulk of gearbox, automotive, and roll-mill applications. Double-row and four-row variants handle heavier combined loads in rolling mills and gear reducers, while thrust versions manage pure axial loads at higher speeds than cylindrical thrust equivalents [S9].
OEM catalogs published between 2024-11-05 and 2026-07-09 expose the full taxonomy: TIMKEN Europe breaks tapered roller bearings into TSF, TSU, TSL, TDI, TDO, TNA, SR, and 2TS-IM series [S1]; NSK Europe Ltd. lists No.2610, No.2612, thin-section, and Molded-Oil variants [S2][S3][S4]; CPM S.p.A. markets custom single- and double-row chrome-steel units from 10 mm bore to 800 mm OD [S5]. Standards governing geometry include ISO 355 for dimensional series, ISO 492 for radial bearing precision, and ABMA/ANSI Std. 19 for inch series tolerances. Reference reading on the broader roller bearing family clarifies where tapered units sit against cylindrical, spherical, and needle alternatives.
Row count and load-direction classification
Single-row tapered roller bearings carry combined radial and axial loads in one direction, with bore ranges documented from 22.23 mm up to 117.48 mm and OD 57.15–180.98 mm on current TIMKEN TSRB product lines [S1]. They are typically adjusted against a second bearing to locate the shaft axially and are the default choice in transmissions, transaxles, and gear reducers [S1][S3].
Double-row variants — TIMKEN TDI (double-row, industrial), TDO (double-row, industrial), TNA (radial double-row), and SR (double-row automotive) [S1] — and CPM S.p.A.'s custom double-row chrome-steel units [S5] handle heavier combined loads or moment loads without requiring a second opposed bearing. Four-row assemblies (e.g. 2TS-IM series) are specified for rolling-mill back-up and work-roll positions where radial load dominates and axial space is constrained. For mill-duty and conveyor applications, the related roller conveyor design pages give context on bearing-supported idler duty cycles.
Thrust and combined-load tapered bearings
Tapered roller thrust bearings use a shaft washer, housing washer, cage, and tapered rollers whose cones intersect on the bearing's central line, giving higher axial limit speeds than cylindrical roller thrust equivalents of the same size [S9]. They are specified where pure axial load is dominant — vertical shafts, crane slew rings, and rolling-mill screw-down mechanisms — and are often paired with a radial tapered-roller-bearing on the same shaft to react residual radial load.
NSK Europe's axial No.2610 (gearboxes) and No.2612 (mining and metallurgical) tapered roller lines [S2] sit in the same combined-load category, with stainless-steel material options for corrosive duty. TIMKEN TSF (axial single-row) and TSU (radial single-row) cover the lower-capacity end of the same combined-load spectrum [S1]. When axial load reverses direction, two single-row bearings are mounted in an O- or X-arrangement; designers should refer to the manufacturer-supplied adjustment procedures for preload and endplay.
Material, precision, and environmental variants
Standard tapered roller bearings use through-hardened carbon-chrome steel (DIN 100Cr6 / AISI 52100, China GB/T 18254 Gcr15) — the 30244 catalog entry explicitly lists Gcr15 as the bearing material [S8]. Case-carburized variants extend impact resistance for heavy industrial service, while NSK's Molded-Oil series uses stainless-steel construction with oil-impregnated polymer lubricant to deliver "operating life more than twice as long as grease lubrication, in water or dust-contaminated environments" [S2]. The Molded-Oil line covers ball, spherical roller, and tapered roller types with contact seals standard on ball versions [S2].
Precision grades follow ISO 492 (P0 / P6 / P5 / P4 / P2) with P2 reserved for machine-tool spindles; the 32007 bearing specifies P2 grade precision tolerance as standard [S6]. NSK's Quick Assembly Taper Roller Bearings target high-precision preload in automotive applications through improved roller stability after cup-and-cone assembly [S3]. Thin-section low-torque tapered roller bearings (NSK) are intended for low-friction, low-torque drives where envelope and drag losses dominate the duty cycle [S4]. Dimensional conformance on metric 30000-series is per ISO 355; inch series J-series follows ABMA/ANSI 19.1.
Size envelope and dimensional series
The bore envelope spans more than an order of magnitude in the published 2026-07-08/09 catalog set: 22.23 mm at the small end (TIMKEN TSRB) [S1], 35 mm for 32007 [S6], 117.48 mm at the high end of the TSRB catalog range [S1], and 220 mm for 30244 [S8]. CPM S.p.A. extends the envelope to 10 mm bore / 800 mm OD for custom mill-duty single- and double-row units [S5]. Width scales with series: 18 mm for 32007 [S6], 73 mm for 30244 [S8], and corresponding increases through the 30200, 30300, 32000, 32200, 32300 metric families.
Dimensional selection is governed by load magnitude, speed factor (n × dm), and mounting envelope; ISO 355 defines seven dimension series (2, 3, 4, 5, 6, 7, 8) by increasing OD for a given bore. Weight follows from geometry: the 32007 weighs 2.0 kg [S6], while the 30244 weighs proportionally more given its 220 × 400 × 73 mm envelope [S8]. For a deeper view of bearing-supported rotation across industries, see the road roller application note covering compaction equipment drum bearings.
Selection criteria: load, speed, environment, adjustment
Selection of a tapered roller bearing type starts with load direction and magnitude: combined radial+axial → single-row or double-row; pure axial → thrust type [S9]; pure radial with high speed → consider cylindrical or crossed-roller-guide alternatives. Within combined load, row count scales with load capacity and moment reaction: single-row for most gearboxes, double-row TDI/TDO for industrial gear reducers, four-row 2TS-IM for rolling-mill work rolls [S1].
Speed is limited by the lubrication regime; thrust variants exceed cylindrical thrust speed limits because of the cone-geometry line contact [S9]. Environment drives material selection: Gcr15 / 52100 for general industrial, stainless with Molded-Oil for corrosive or wash-down duty [S2][S8]. Adjustment method matters operationally — single-row units require a second opposed bearing for axial location, while double-row TDI/TDO types are factory-set and pre-located [S1]. For related specification work on mechanical-power drivetrains, the roller chain encyclopedia entry covers the parallel decision space for chain drives versus geared bearing arrangements.
Specification comparison: principal tapered roller bearing types
The table below lines the main types up against four decision criteria based on the OEM catalogs cited: load direction, typical bore range, common application, and material/lubrication option. Sources are cited per row so engineers can pull the originating catalog page. [S1]
Single-row TSRB / 30000-series [S1][S6][S8]: combined radial+axial, bore 22.23–117.48 mm, automotive transmission and machine-tool spindle, through-hardened carbon-chrome steel with grease. Single-row thin-section low-torque [S4]: combined radial+axial at reduced drag, bore range within NSK thin-section envelope, low-friction drives, steel with optimized surface finish. Double-row TDI / TDO / TNA [S1]: combined heavy load, bore matches 30000-series envelope, industrial gear reducers and rolling mills, steel. Four-row 2TS-IM [S1]: heavy radial with axial component, mill-duty envelopes, rolling-mill work and back-up rolls, steel. Thrust tapered roller [S9]: pure axial high-speed, full envelope per ISO 355, vertical shafts and screw-down, steel with oil or grease. Molded-Oil stainless tapered [S2]: combined load in corrosive/dust service, NSK envelope, agriculture / chemical / food / mining, stainless steel with oil-impregnated polymer.
Common failure modes and sourcing signals
Premature tapered roller bearing failure traces to four dominant causes: contamination (the primary motivator behind NSK's Molded-Oil contact-sealed line [S2]), inadequate lubrication (Grease life is the limiting factor; Molded-Oil claims "more than twice" grease life in water/dust [S2]), misalignment (single-row units are particularly intolerant — even 0.001 rad of misalignment can shorten fatigue life), and overload (over-spec combined loads on a single-row rather than a double-row). Burnishing marks, spalling on the cup raceway, and roller-end scuffing are the diagnostic signatures.
Sourcing signals from the 2026-05 to 2026-07 catalog window point to active supplier activity in metric 30000-series (Tianjin Huaxin on 32007 [S6], Hubei Parts Service on 30244 [S8]) and a widening Molded-Oil / stainless option set from NSK [S2]. Wuxi Jianfa Bearing Technology (Wuxi, Jiangsu) lists brass-cage tapered roller bearings among its main products on Made-in-China.com [S10], and Linqing City Risheng advertises medium-to-large metric and spherical units with material/hardness guarantees [S7]. For spec selection that sits next to tapered roller bearings in driveline design, see the Self-Aligning Bearing Advantages, Disadvantages, and Spec-Driven Selection piece — it covers the alternative misaligned-shaft cases where a self-aligning bearing replaces a two-row tapered arrangement.
Trackable signals to watch over the next two quarters: ISO 492 precision-class updates in any newly cited TIMKEN TSF/TSU catalog reissues [S1], NSK Molded-Oil envelope expansion past the current 22 mm minimum bore [S2], and metric 30000-series supply stability from Tianjin and Hubei suppliers [S6][S8] — these three nodes will indicate whether the 2026 spec map shifts toward higher-precision or higher-environmental-resistance variants.