Timken6578Tapered Roller Bearing Cone Only 4-3/4 inch ID Straight Bore Inch Series (Cup Not Included)

Product Description

What this part is

A Timken 6578 tapered roller bearing cone: the inner ring complete with its tapered rollers and cage, for a 4-3/4 inch straight bore shaft. This is an inch-series industrial cone, the kind used in gearboxes, wheel ends, pinion shafts, conveyor heads and heavy machinery where combined radial and one-way thrust load has to be carried.

What is in the box

Cone only. A tapered roller bearing is a two-piece bearing — the cone (inner ring, rollers and cage) and the cup (the outer race). This listing is the cone. The cup is a separate part number and is not included, so unless the existing cup in the machine is sound and staying in place, a cup has to be bought as well.

What these specs mean in practice

Cone and cup are not independent parts. Timken publishes each cone against the specific cup or cups it is designed to run with, and the pair sets the contact angle, the load ratings and the internal setting of the bearing. Mixing a cone with a cup it was not designed for gives incorrect roller-to-raceway geometry and the bearing will not make its rated life, even if the parts appear to fit. A single tapered roller bearing carries thrust in one direction only, so the shaft normally runs two of them opposed.

Published specifications

Component: cone (inner ring with rollers and cage)Bore: 4-3/4 inch, straightSeries: inch, Timken 6578Rows: singleBearing type: tapered roller

Quantity and configuration

One cone. If the machine uses two opposed tapered roller bearings, both positions will need their own cone and cup.

Fitting notes

Check the number stamped on the cup already in the housing before ordering, and match this cone to that cup number rather than assuming. Heat the cone for mounting rather than pressing it cold onto a heavy interference fit, and never drive mounting force through the rollers. Tapered roller bearings are set at assembly: end play or preload has to be established to the machine builder’s figure using shims, a spacer or the adjusting nut, because the bearing has no built-in internal clearance until it is set. Handle the roller set carefully — a cone with a nicked roller or a bent cage is scrap.

Interchange guidance

Cross-references cover the 6578 designation in its spaced and hyphenated forms. Note the distinction that catches buyers out: a cone number, a cup number and a complete assembly number are three different things. Timken numbers with a -90xxx suffix are complete assemblies, not cones. If a full bearing is needed rather than a replacement inner, that is a different part number.