An inch-series tapered roller bearing is identified by a paired cone/cup set number, not a single assembly code, with a typical entry-level set such as LM11749/LM11710 measuring 0.68" bore x 1.57" OD x 0.545" width [S4].
The cone is the inner ring plus rollers and cage, the cup is the outer ring, and the set number printed on the bearing is the two halves joined by a slash, which is the convention used across the ABMA inch series carried by Timken, SKF, Koyo, NTN, and the major aftermarket brands [S1][S3][S6].
Why Inch-Series Tapered Roller Bearings Use a Two-Part Number
Each tapered roller bearing is a four-component assembly: cone (inner ring), cup (outer ring), tapered rollers, and a cage, and because the cone and cup are separable they have always carried individual Timken-style designations that the catalog then lists as a "set" [S3].
An inch-series set number such as LM67048/LM67010 is therefore not a single part code but a pairing: LM67048 is the cone half (1.25" bore), LM67010 is the cup half (2.32" OD, 0.625" width), and a maintenance buyer ordering spares will see both numbers on the original equipment drawing and on the surplus listing [S4][S6].
The convention exists because the cup and cone from two different bearings of the same series and the same manufacturer are usually interchangeable, so the catalog can list them either as a matched set or as separate components, which simplifies field replacement when only one half is worn [S2][S5].
Set Numbers, Component Codes, and the lm/l-M Suffix Logic
Imperial prefix letters are not decorative: the LM, L, M, and JL prefixes on common inch-series cones and cups encode bore range and cross-section family rather than a sequential size, which is why part numbers like L44643/L44610 (1.00" bore) and L44649/L44610 (1.06" bore) can share the same cup but need different cones [S4].
Concrete data points from a current aftermarket listing: LM11749/LM11710 at 0.68" x 1.57" x 0.545" wide, LM11949/LM11910 at 0.75" x 1.78" x 0.61", M12649/M12610 at 0.84" x 1.96" x 0.69", LM67048/LM67010 at 1.25" x 2.32" x 0.625", 15123/15245 at 1.25" x 2.44" x 0.75", LM501349/LM501310 at 1.62" x 2.89" x 0.77", and LM29749/LM29710 at 1.50" x 2.56" x 0.71" [S4].
The set number is the only practical identifier on the bearing itself, and a worn cup can be mated with multiple cones of the same series from the same manufacturer, which is why a cup such as LM11710 will reappear across several set listings and never on its own [S4][S5].
Metric 30200-Series vs Inch-Series Naming
The ISO 355 / DIN 720 metric series uses a single part number per assembly rather than a paired cone/cup set, with 30202 at 15 mm bore x 35 mm OD x 11.75 mm width, 30204 at 20 x 47 x 15.25, 30210 at 50 x 90 x 21.75, and 30220 at 100 x 180 x 37.00, all listed as single codes in supplier charts [S2].
For metric 30200-series sizes, the bore code logic is the only shortcut: for 04 and above, multiply the last two digits of the part number by 5 to get the bore in mm (30204 gives 04 x 5 = 20 mm; 30220 gives 20 x 5 = 100 mm), a rule that sanity-checks against every row in a verified supplier chart [S2].
Dynamic and static load ratings for the metric 30200 series scale cleanly with bore: Cr rises from 16 kN at 30202 to 255 kN at 30220, while C0r climbs from 14 kN to 330 kN over the same range, a roughly 16x capacity increase that designers can plot against shaft diameter [S2].
Cross-Brand Mating and Interchange Limits
A cone from one manufacturer generally should not be paired with a cup from another brand unless the manufacturer explicitly certifies cross-brand interchange for that size, because contact angle, roller profile, and crowning are tuned per maker and the catalog states this boundary plainly [S2].
Within a single brand, the practical rule from the workshop side is that a given cup can be mated with multiple cones of the same series, which is the engineering reason both halves are kept as separate part numbers rather than collapsed into one [S5].
The 8482.20.00.20 HTSUS sub-heading used by US importers treats "tapered roller bearings, cup and cone" as a single customs line, so the paired naming also has to survive freight classification on cross-border shipments, not just technical drawings [S7].
Decision Matrix: When to Order the Set vs Separate Components
For new equipment, wheel-hub duty, and gearbox shaft applications where the full unit is being replaced, ordering the hyphenated set (LM67048/LM67010 or 15123/15245, for example) is the cleanest path and matches what is printed on the OEM drawing [S4].
For rebuilds where only the cone is worn (typical on a shaft that has been reground undersize) or only the cup is damaged (typical after a housing distortion event), ordering a single half from the same series and same brand is supported by the catalog, with the cup as the most commonly re-used component [S4][S5].
For metric designs following roller bearing ISO 355 conventions, the single 30200-series code is the part number; there is no paired cone/cup set number on the bearing, and any apparent split designation in a supplier listing refers to inventory rather than a different part identity [S2].
Failure Modes and Procurement Pitfalls
The single biggest field failure on inch-series rebuilds is mismatched half-life: replacing only the cone while leaving a worn cup in service, or pairing a new cone with a cup from a different brand, both of which the catalog flags as invalid configurations [S2][S5].
Width is the dimension most often misread on a worn or relabeled bearing, because bore and OD are easy to confirm with calipers but the assembled stack height of cone plus cup plus rollers (T) gets missed when a cone and cup from different production runs are already stacked together [S2].
When mating surfaces, load cases, or tolerances matter for construction machinery and equipment and other heavy-duty hosts, the cup and cone should come from a single set number on the OEM data plate rather than from two separately sourced halves [S3][S4].
Sourcing Standards and Documentation
The four-component definition (cone, cup, rollers, cage) and the set-number convention are documented in the Timken tapered roller bearing catalog, which is the de facto reference for the ABMA inch series carried across the major brands [S3].
Metric 30200-series dimensions and load ratings follow DIN ISO 355 / DIN 720 as the controlling dimensional standards, and these are the lines that most Chinese, Japanese, and European makers publish against in their public charts [S2].
Customs classification under HTSUS 8482.20.00.20 treats cup and cone tapered roller bearings as one line, so a paired set number on the commercial invoice and a single paired OEM code on the parts list both clear the same tariff line without a separate ruling [S7].
For comparison with adjacent bearing-system decisions on the same kind of equipment, tapered roller bearings in wheel hub versus gearbox shaft duty covers the application-side split, while taper lock bush angle and taper ratio is the matching reference for the bushed-hub side of the same shaft. For metrology context on the bearings themselves, hard-bearing vs soft-bearing balancing machines sits next to this in the workflow.