TimkenClass 3 Precision Tapered Roller Bearing Cone Only, 4.2500 in Bore x 1.3750 in Inner Ring Width, Inch Series – Mating Cup Not Included

Product Description

What this part is

This is the cone half of a single-row tapered roller bearing: the inner ring with its ground tapered raceway, the tapered rollers, and the cage that retains them, supplied as one non-separable assembly. It is the Timken 48190 cone in Class 3 precision, 4.2500 in (107.95 mm) bore by 1.3750 in (34.925 mm) inner ring width. The cone is the half that presses onto the shaft.

Scope of supply

This listing is the cone only. The mating cup is not included. The cup for this cone is the Timken 48120, given on Timken’s catalogue entry for the 48190. A tapered roller bearing is two separately numbered halves: the cup (outer ring) presses into the housing, the cone (inner ring plus rollers plus cage) presses onto the shaft. The two halves mount in different members and wear at different rates, so they are catalogued and sold separately.

Decoding the designation

48190: Timken inch-series cone part number. The cone number selects the bore, and 48190 gives the 4.2500 in shaft fit.

48120: the mating cup number in the same series. Together they form the 48190 / 48120 single-row assembly.

-3, also written *3 or #3: a Timken precision class suffix denoting Class 3, not a variant or a revision.

Class 3 precision

Timken’s inch tapered roller precision ladder runs from standard class through Class 3 and on to Class 0 and Class 00, each step tightening the tolerances. Class 3 is the first precision step above standard. Class 00 is tighter still, so a Class 00 requirement is not met by a Class 3 part.

Class 3 tightens control on the bore diameter and on the raceway geometry, and tightens running accuracy: less radial and axial runout as the bearing turns. That matters in positions where the bearing sets the position of something rather than merely carrying it, such as machine-tool spindles, precision gearboxes, index and rotary tables, boring and grinding heads, and test and measuring equipment. Runout at the bearing transfers directly into the gear mesh or the workpiece.

A Class 3 cone takes extra grinding and gauging to produce and costs more than a standard-class 48190.

Published ratings

Load ratings below are Timken’s published figures. They describe the complete 48190 / 48120 single-row assembly rather than the cone in isolation, because capacity is a property of the roller set running between both raceways. Bore, inner ring width, weight and shaft abutment figures are cone-specific.

Cone bore (d): 4.2500 in / 107.95 mm.

Inner ring width (B): 1.3750 in / 34.925 mm.

Precision class: Class 3.

Mating cup: 48120.

Dynamic radial load rating C1 (1 million revolutions, ISO method): 43,200 lbf / 192,000 N.

Dynamic radial load rating C90 (90 million revolutions, Timken method): 11,200 lbf / 49,800 N.

Dynamic axial rating Ca90: 9,680 lbf / 43,100 N.

Static radial load rating C0: 69,200 lbf / 308,000 N.

K factor: 1.16.

Effective centre location (a): 0.15 in / 3.8 mm.

G1 factor: 180.

G2 factor: 44.7.

Geometry factor Cg: 0.156.

Cone weight: 5.2 lb / 2.3 kg.

Mounting data

Maximum shaft fillet radius cleared: 0.14 in / 3.560 mm.

Shaft backing shoulder diameter, frontface (da): 4.57 in / 116 mm.

Shaft backing shoulder diameter, backface (db): 4.8 in / 122 mm.

Cage location relative to backface (Aa): 0.09 in / 2.3 mm.

Cage location relative to frontface (Ab): 0.07 in / 1.8 mm.

The cone is an interference fit on the shaft.

A tapered roller bearing has no built-in internal clearance. The operating clearance or preload is created at assembly by how far the cone is drawn up against the cup, and that setting is the largest single determinant of both bearing life and spindle accuracy.

What these specs mean in practice

The K factor of 1.16 describes the duty this bearing was drawn for. K is the ratio of radial to thrust capability, fixed by the cup angle: the lower the K, the steeper the angle and the more thrust the bearing carries for a given radial load. At 1.16 the 48190 / 48120 is a comparatively steep-angle bearing, with a published Ca90 of 9,680 lbf against a C90 of 11,200 lbf, so it takes substantial axial load alongside the radial reaction. That is the profile of a bevel or helical gear shaft, or a spindle taking cutting thrust, rather than a plain radial support position.

C1 and C90 describe the same bearing at two different life bases: C1 (43,200 lbf) at one million revolutions on the ISO method, C90 (11,200 lbf) at ninety million revolutions on Timken’s method. G1, G2 and Cg are the constants for Timken’s own life arithmetic, with Cg feeding the lubrication life adjustment factor a3l.

Quantity and configuration

One cone, priced and sold as a single piece. The condition note records that this cone came out of a factory-new set and is factory-packed with grease: a new set was split and this is the cone half. It is unused rather than a pull.

Single-row tapered roller bearings normally work in opposed pairs, because one row resists thrust in one direction only. A typical shaft therefore takes two cones and two cups.

Interchange guidance

48190 is an industry-standard inch cone designation rather than a Timken-proprietary code, and cones to this number are produced by several manufacturers, so a same-number cone from another maker is dimensionally interchangeable in the standard class. The precision class does not interchange: a standard-class 48190 fits the same envelope but does not deliver Class 3 running accuracy, and a Class 00 requirement is not met by a Class 3 part.

Searchable forms: 48190-3, 48190 *3, 48190#3, 48190 #3, 48190*3, 48190 Class 3, and the unsuffixed standard-class 48190, plus 48-190, 48 190 and K-48190. Mating cup: 48120, 48-120, 48 120. Complete assembly designations: 48190/48120, 48190-48120, 48190/48120-3.