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 new takeouts from double-cup sets, removed unused from L521948 / L521910D two-row assemblies. A TDO assembly uses two cones and one double cup, so breaking sets down yields cones in pairs. Where the cup is still serviceable, with an unworn raceway and no spalling or brinelling, a cone-only replacement is the standard repair.

Decoding the designation

L521948 is the 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, so L521948 and L521949 are 4.250 in bore and L521945 is 4.000 in. On 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. Precision Class: Not specified. No precision-class suffix is present on this reference; Timken suffixes such as −3 and −2 denote Class 3 and Class 2.

Published ratings

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 mm. Cup outside diameter (D): 5.7500 in / 146.050 mm. Assembly width (T): 0.8438 in / 21.433 mm. Cone width (B): 0.8438 in / 21.433 mm. Cup width (C): 0.6563 in / 16.67 mm. Dynamic radial load rating C1 (1 million rev, ISO): 20,000 lbf / 88,900 N. Dynamic radial load rating C90 (90 million rev, Timken method): 5,180 lbf / 23,100 N. Dynamic axial rating Ca90: 3,480 lbf / 15,500 N. Static radial load rating C0: 39,400 lbf / 175,000 N. e factor 0.39, K factor 1.49, Y factor 1.53. Assembly 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 thrust is ignored 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.

Quantity and configuration

These are individual cones, not sets. The listing title carries “2 Pcs” because they came out of two-cone double-cup assemblies and are commonly bought in twos to rebuild a TDO unit; the stock is counted and sold as single cones. A two-row assembly rebuild takes two cones and one L521910D double cup; replacing one row of a single-row arrangement takes one cone.

Mounting data

Shaft backing shoulder diameter, frontface (da): 4.49 in / 114 mm; backface (db): 4.57 in / 116 mm. Housing backing shoulder diameter, frontface (Da): 5.57 in / 141.00 mm; backface (Db): 5.35 in / 135.89 mm. Maximum shaft fillet radius: 0.060 in / 1.5 mm. Maximum housing fillet radius: 0.06 in / 1.52 mm. Effective load centre: 0.19 in / 4.8 mm. Cage location relative to backface (Aa): 0.01 in / 0.3 mm; relative to frontface (Ab): 0.1 in / 2.5 mm. G1 Factor: 152. G2 Factor: 108. Geometry Factor Cg: 0.135.

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.

Interchange guidance

L521948 is an industry-standard inch cone designation, so an L521948 from any 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.