TimkenL521948Tapered Roller Bearing Cone Assembly, 4.250 in Bore x 0.8438 in Wide, L521900 Inch Series, Cone Only

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 matching cup (outer ring), which is a separate component and is not included here.

What is and is not included

Cone assembly only: inner ring, rollers, cage. No cup. These are described as new takeouts from double-cup sets, meaning they were removed unused from L521948 / L521910D two-row assemblies. That is worth understanding rather than glossing over, because it explains both the price and the quantity: a TDO 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; L521948, L521945 and L521949 are cones, L521910 and L521914 are cups.The cone number sets the bore. L521948 and L521949 are 4.250 in bore; L521945 is 4.000 in.L521910D — the trailing D marks a double cup, the single wide outer ring used in a two-row TDO assembly. Two L521948 cones plus one L521910D double cup make up a complete two-row unit.

Published ratings and mounting data

Figures below are Timken’s published data for the L521949 / L521910 single-row assembly, which shares this cone’s bore, section and internal geometry. A cone has no 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 rev, ISO): 20,000 lbf / 88,900 NDynamic radial load rating C90 (90 million rev, 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 mmMaximum 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 — a steeper cup angle than a pure radial-duty bearing, so it takes a useful axial component alongside its radial load. That is the combination gear-driven shafts need, and it is why the L521900 series appears 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

Forty pieces are on hand and they are individual cones, not sets. The listing title carries “2 Pcs” because these came out of two-cone double-cup assemblies and are commonly bought in twos to rebuild a TDO unit — but the stock is counted and sold as single cones. 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.

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, so an L521948 from any reputable maker is dimensionally interchangeable. Cross-references: L521948, L-521948, L 521948. Same-bore sibling cone: L521949. Mating cups: L521910, L521914 (4.250 in bore with 6.000 in outside diameter), L521910D double cup. Related assemblies: L521949/L521910, L521949/L521914, L521948/L521910D and L521949/L521910D.

Central Surplus also stocks the complete Timken 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.