Timken390A-3Tapered Roller Bearing Cone, 2.5000 in / 63.500 mm Bore, 0.8660 in Wide, Class 3 Precision, Cone Only

Product Description

What this part is

A Timken 390A single tapered roller bearing cone in Class 3 precision: the inner ring with its full tapered roller set and cage, one half of a tapered roller bearing. Cone only. The matching cups are Timken 394A, 394AS and 3920. The 390A is one of the most widely used inch cones in the 2-1/2 in bore range, appearing in gearboxes, trailer and axle hubs, agricultural drives and general industrial shafting.

Decoding the designation

390: Timken imperial TS cone sequence. A: design revision within the sequence. -3: Timken precision Class 3, a tighter bore, width and runout grade than the standard Class 4 / K tolerance. Cartons stamp it with a leading asterisk, so the part also reads 390A *3 and 390A3.

Specifications

Manufacturer: The Timken Company. Part Number: 390A-3. Base Number: 390A. Cone Part Number: 390A. Bearing Type: tapered roller bearing cone, single row, TS series. Series: Timken imperial TS tapered single, 390 sequence. Bore (d): 2.5000 in / 63.500 mm. Cone Width (B): 0.8660 in. Bore Type: straight. Number of Rows: 1. Precision Class: Timken Class 3. Bearing Class: Class 3. Cage Type: stamped one-piece roller cage. Cage Material: steel. Bearing Material: case-carburized steel. Closure Type: open. Cone Backface To Clear Radius: 0.06 in. Cone Frontface Backing Diameter: 2.76 in. Cage-Cone Frontface Clearance: 0.11 in. Cage-Cone Backface Clearance: 0.05 in. Effective Center Location: -0.03 in. Design Units: imperial (inch). Harmonization Code: 8482.20.00. Mating Cups: 394A, 394AS, 3920.

What these specifications mean in practice

The 390A is a relatively narrow cone for its bore: moderate thrust capacity, good radial capacity, compact axially. Tapered rollers carry combined radial and one-way thrust because the roller and raceway apexes meet at a common point, so they are fitted in opposed pairs and the pair’s axial setting is established at build. Class 3 tightens bore, width and runout, which makes a dialled-in endplay repeatable and keeps a gear contact pattern stable.

Quantity and configuration

Cone assembly only: inner ring, tapered rollers and cage as one non-separable unit. Unit Quantity: 1 Pc.

Interchange guidance

Standard assemblies are 390A/394A and 390A/3920. Inch tapered roller numbering is an industry standard rather than a brand code, so Koyo 390A, NTN 390A, SKF 390A, Bower/BCA 390A and Federal-Mogul 390A describe the same cone. Timken 390A without the -3 suffix is the same cone in standard Class 4 / K precision.