TimkenNA56424A-3Tapered Roller Bearing Cone, 4.2500 in / 107.950 mm Bore, 1.4375 in Wide, Class 3 Precision, Cone Only

Product Description

What this part is

A Timken NA56424A single tapered roller bearing cone in Class 3 precision — the inner ring together with its tapered roller set and cage, one half of a tapered roller bearing. The cup (outer race) is the separate 56650 part number and is not included in this listing. At a 4-1/4 in bore this is a heavy industrial cone, the kind used in mill stands, large gearbox shafts, kiln and conveyor pulleys and press drives.

Decoding the designation

NA – Timken cone series prefix denoting the higher-capacity roller complement design within the 56400 sequence, as distinct from the plain 56425 cone in the same envelope.
56424 – cone number in the 56400 sequence, mating the 56650 cup.
A – design revision within the sequence.
-3 – Timken precision Class 3, tighter bore, width and runout than the standard Class 4 / K grade. Cartons often stamp this as a leading asterisk, so the part also reads NA56424A *3 and NA56424A3.

Published dimensions

Bore (d): 4.2500 in / 107.950 mm
Cone width (B): 1.4375 in
Mating cup: 56650 — O.D. 6.500 in, cup width 1.063 in
Rows: 1
Precision: Timken Class 3
Bore type: straight

What these specs mean in practice

Tapered rollers carry heavy combined radial and one-way thrust because roller and raceway apexes converge on a common point, so they are used in opposed pairs and the pair’s axial setting is dialled in at assembly. In this size range the cone is a big axially-stiff component and the abutment matters as much as the fit — a shoulder that is not square will cock the cone and show up as an uneven roller-end wear pattern within hours of running. Class 3 tightens bore, width and runout so the setting is repeatable, which is what large gear drives and roll positions need to hold a contact pattern.

Quantity and configuration

This listing is the cone assembly only — inner ring, rollers and cage as one non-separable unit. No cup and no spacer are included. The mating 56650 cup is ordered separately; cups and cones from the same sequence are frequently on the shelf here together and can ship as a complete bearing.

Fitting notes

Induction heat the cone or press against the backface only — never through the rollers or the cage, and never with an impact tool at this diameter. Check the shaft backing shoulder for squareness and full contact before pressing. Lubricate the roller set, then set endplay or preload to the machine builder’s figure and re-check once the housing has come up to operating temperature.

Interchange guidance

The standard assembly is NA56424A/56650, and the related two-row form is NA56425SW/56650CD. Inch tapered roller numbering is an industry standard, so Koyo NA56424A, NTN NA56424A and the shortened trade forms 56424A and 56424 all point at this cone. The plain 56425 shares the same bore and cup and is carried here as a dimensional cross-reference — it is the standard-complement cone in the same envelope, so ratings differ even though it will fit. A plain NA56424A without the -3 suffix is the same cone in standard Class 4 / K precision and substitutes wherever the tighter class is not called out.