TimkenTapered Roller Bearing Cone 2-7/8 in Bore, Timken Class 3 Precision

Product Description

What this part is

A Timken 42683-3 tapered roller bearing cone — the inner ring complete with its tapered rollers and cage, 2-7/8 in bore, produced to Timken Class 3 precision. The cone is the half of a tapered roller bearing that goes onto the shaft.

Quantity and configuration

1 Pc. Cone only. The matching cup is the Timken 42620.

Decoding the designation

42683 is the cone number and fixes the bore, the cone width and the raceway angle together. The trailing 3, written as -3 or *3 or #3, is Timken precision Class 3 — tighter than Class 2 and tighter again than the standard commercial class, held on bore, raceway form and running accuracy. The Class 3 grade is marked on the cone and stated on the carton.

What these specs mean in practice

Class 3 is chosen where shaft runout and repeatable bearing setting matter more than they do in general service: machine tool tables and spindles, printing and converting rolls, gear test stands, and precision indexing drives. The tighter bore and raceway tolerances mean the set clearance lands in a narrower band on assembly, so the same shim stack reproduces the same setting from one rebuild to the next. The cone assembly is a unit — inner ring, rollers and cage are not separable, and the rollers are matched to that ring.

Fitting notes

The cone presses onto the shaft with the force applied to the inner ring back face only, never through the rollers or the cage. Once both races are seated, the bearing is set by moving one race axially against the other to reach the intended end play or preload, held to a tighter band than on a standard-class bearing.

Interchange guidance

A cone marked 42683 from another tapered roller bearing maker shares the bore, width and raceway angle and takes the same 42620 cup. A plain 42683 is standard class, so it is a related part rather than a substitution where the Class 3 grade is the reason for the specification. The 42688 and 42690 are different bores in the same numbering family and are related sizes.