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. The parts supplied are the inner ring, the tapered rollers and the cage. A complete bearing also takes the mating cup, an L521910 or L521914 single cup, or an L521910D double cup for a two-row arrangement. Cup and cone are separately numbered halves of one bearing.

These are new takeouts from double-cup sets, removed unused from L521948 / L521910D two-row assemblies. A two-row 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: L521945, L521948 and L521949 are cones, L521910 and L521914 are cups. The cone number selects 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 assembly, and two L521948 cones plus one L521910D double cup make 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

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, because a cone has no load rating in isolation.

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 revolutions, ISO method): 20,000 lbf / 88,900 N. Dynamic radial load rating C90 (90 million revolutions, 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. 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 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 and not pairs. 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 rather than a proprietary Timken code, so it is manufactured by several bearing makers and an L521948 from any source is dimensionally interchangeable. 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.