TimkenL521948Tapered Roller Bearing Cone Assembly 4-1/4 in Bore, 0.8438 in Wide, Inch Series — Cone Only, No Cup

Product Description

What this part is

This is a tapered roller bearing cone assembly — the inner ring complete with its tapered roller set and cage. It is the L521948 cone from Timken’s L521900 inch series, with a 4.250 in (107.95 mm) bore and a cone width of 0.8438 in (21.433 mm). The cone runs inside a mating cup, which is the outer ring and a separately numbered component.

What is and is not included

This listing is the cone assembly only. There is no cup. You receive the inner ring, the tapered rollers and the cage — nothing else. If you need a complete bearing you must also source the mating cup, which is an L521910 or L521914 single cup, or an L521910D double cup for a two-row arrangement. This is the single most expensive mistake made when buying tapered roller bearings: cup and cone are separately numbered halves of one bearing, and an order for a cone number brings you half a bearing.

These are new takeouts from double-cup sets, meaning they were removed unused from L521948 / L521910D two-row assemblies. That explains both the price and the quantity: a two-row assembly uses two cones and one double cup, so breaking sets down yields cones in pairs. If your cup is still serviceable — unworn raceway, no spalling, no brinelling — a cone-only replacement is the standard and considerably cheaper repair.

Decoding the designation

L521948 — Timken inch-series cone number in the L521900 series. Cones and cups are numbered separately within a series: L521945, L521948 and L521949 are cones, L521910 and L521914 are cups.The cone number selects the bore. L521948 and L521949 are 4.250 in bore; L521945 is 4.000 in. If the bore is what you are matching, the cone number is the number that matters.L521910D — the trailing D marks a double cup, the single wide outer ring used in a two-row assembly. Two L521948 cones plus one L521910D double cup make a complete two-row unit.No precision-class suffix is present on this reference, so it is a standard-class cone. Timken suffixes such as −3, −2 and −00 denote tighter precision classes and are absent here.

Published ratings and mounting data

The figures below are Timken’s own published data for the L521949 / L521910 single-row assembly, which shares this cone’s bore, section and internal geometry. They describe the bearing as a pair, not the cone alone — a cone has no load rating in isolation, because capacity depends on the roller set running between both races.

Bore (d): 4.2500 in / 107.95 mmCup outside diameter (D): 5.7500 in / 146.050 mmAssembly width (T): 0.8438 in / 21.433 mmCone width (B): 0.8438 in / 21.433 mmCup width (C): 0.6563 in / 16.67 mmDynamic radial load rating C1 (1 million revolutions, ISO method): 20,000 lbf / 88,900 NDynamic radial load rating C90 (90 million revolutions, Timken method): 5,180 lbf / 23,100 NDynamic axial rating Ca90: 3,480 lbf / 15,500 NStatic radial load rating C0: 39,400 lbf / 175,000 Ne factor 0.39, K factor 1.49, Y factor 1.53Shaft backing shoulder diameter, frontface (da): 4.49 in / 114 mm; backface (db): 4.57 in / 116 mmHousing backing shoulder diameter, frontface (Da): 5.57 in; backface (Db): 5.35 inMaximum shaft fillet radius cleared: 0.06 in / 1.5 mmEffective centre location: 0.19 in / 4.8 mmCage location relative to backface (Aa): 0.01 in / 0.3 mmAssembly weight, cone plus cup: 2.2 lb / 1 kg

What these specs mean in practice

A K factor of 1.49 puts this series in the middle of the tapered roller range. K is the ratio of radial to thrust capability set by the cup angle, so a mid-range K means a steeper cup angle than a pure radial-duty bearing and a useful axial component carried alongside the radial load. That is the combination gear-driven shafts need, and it is why the L521900 series turns up in industrial gearboxes, wheel hubs and pinion positions.

The e factor of 0.39 is the load-ratio threshold in the equivalent-load equation: below an axial-to-radial ratio of 0.39 you ignore thrust in the calculation, above it the equation changes. Together with K = 1.49 and Y = 1.53 that is everything needed to run a bearing life calculation, and all three are published above rather than estimated.

Quantity and configuration

Sixty-two pieces are on hand and they are individual cones, not sets and not pairs. If you are rebuilding a two-row assembly you need two cones and one L521910D double cup; if you are replacing one row of a single-row arrangement you need one cone. Order the count you actually need and do not assume a piece is a pair. A quantity this deep from one source is worth knowing about if you have several identical positions to rebuild, because it lets you fit the whole machine from one production vintage.

Fitting notes

The cone presses onto the shaft, and the 0.06 in maximum shaft fillet radius must be cleared at the shoulder or the cone will sit cocked and the roller set will run with a skewed load line. Heat the cone or use a fitting tool that pushes on the inner ring face — never drive against the cage or the rollers.

Tapered roller bearings carry no built-in internal clearance. Operating endplay or preload is created at assembly by how far the cone is drawn against the cup, and that setting governs bearing life more than any other single variable. Fitting a new cone against a used cup changes the stack-up, so re-measure and re-set endplay to the machine builder’s figure rather than reusing the old shim pack.

Interchange guidance

L521948 is an industry-standard inch cone designation rather than a proprietary Timken code, so it is manufactured by several bearing makers and an L521948 from any reputable source is dimensionally interchangeable. That widens your options considerably if Timken stock is unavailable. Cross-references: L521948, L-521948, L 521948, K-L521948. Same-bore sibling cone: L521949. Mating cups: L521910, L521914, L521910D double cup. Related assemblies: L521949/L521910, L521949/L521914, L521948/L521910D, L521949/L521910D.

Central Surplus also stocks this same L521948 cone as a separate lot under SKU BAY3#3VA4EO, and the complete L521948 / L521910D double cone-and-cup assembly under SKU B-AO5B4#ONPOPU. If you need the cup as well as the cone, buy the assembly rather than sourcing the cup separately.