Timken559-WTapered Roller Bearing Cone Only 2-1/2″ Bore 1.4440″ Wide Class 3 Series 555

Product Description

What this part is

This is a single-row tapered roller bearing cone — the inner ring, complete with its tapered rollers and cage, in the 555 series. It is not a complete bearing. A tapered roller bearing is a two-piece assembly: the cone (inner ring plus roller and cage set) and the cup (the separate outer race). This listing covers the cone only, and no cup is included. That is the single most important fact on this page, because a cone by itself will not carry load. If your housing bore already has a serviceable cup pressed into it, a cone-only replacement is exactly what you want. If the cup is spalled, brinelled or has a wear step at the large end of the raceway, you need to buy the matching cup as well.

Published cone dimensions

Bore (d): 2.5000 in / 63.500 mmCone width (B): 1.4440 in / 36.678 mmSeries: 555Cage: one-piece stamped steelMaximum shaft fillet radius (R): 0.14 in / 3.5 mmCone backing shoulder diameter (da): 72 mmCone backing shoulder diameter (db): 78 mmCone weight: 1.216–1.275 kg depending on published source

Which cups this cone runs against

Timken lists the 559 cone as matching the 552, 552A, 552B, 552D, 552DC, 553A and 553X cups. Those cups are not interchangeable with each other for setting purposes even though they share the family — they differ in outside diameter, cup width and therefore in the overall assembly width T. Identify the cup that is actually in your housing before ordering, either from the marking on the cup face or by measuring the housing bore. Getting this wrong is the most common cause of a taper set that cannot be brought to the correct endplay.

Assembly data when paired with the 552A cup

The 559 cone with a 552A cup is catalogued by Timken as assembly number 559-99401. Published data for that assembly:

Bore d: 2.5000 inCup outside diameter D: 4.8750 inAssembly width T: 1.5000 inCup width C: 1.1875 inEffective load center a: −9.4 mmHousing shoulder diameters: Da 116 mm, Db 109 mmHousing fillet radius r: 3.3 mmLoad factors: e 0.35, Y 1.73, K 1.69Dynamic radial rating C1: 226,000 NC90: 58,600 N — Ca90: 34,700 NStatic rating C0: 248,000 NAssembly weight: 1.98 kg
Published ratings for this set are not consistent across sources. Timken assembly data gives C1 226,000 N and C90 58,600 N, while at least one distributor (Simply Bearings) publishes C1 177,000 N and C90 45,800 N for the same pairing. We cite the Timken figures above and disclose the discrepancy rather than quietly picking one. If your calculation is anywhere near the margin, work from the lower number or get the rating confirmed by Timken engineering before you commit.

What the K, e and Y factors actually do for you:
These are not decoration. K is the ratio of radial to thrust load capability and is what you use to convert a measured or calculated thrust load into an equivalent radial load for life calculation. e is the threshold ratio of axial to radial load above which the thrust component starts to change how the load is shared among the rollers, and Y is the thrust factor applied above that threshold. In a two-bearing taper arrangement these factors are also how you work out how much of the thrust each row is actually seeing, which drives the setting you should be targeting. If you are simply replacing like for like on a machine that has been running correctly, you can ignore them. If you are re-rating a drive or increasing speed or load, they are the numbers that matter.

Why Class 3 is tighter than Class 2

Timken’s inch tapered roller bearing precision classes follow ANSI/ABMA Standard 19.2, and the numbering is genuinely counter-intuitive. The sequence from loosest to tightest is Class 4 → Class 2 → Class 3 → Class 0 → Class 00. So Class 3 is tighter than Class 2 and looser than Class 0. Buyers routinely assume a higher number means a tighter tolerance and order the wrong part on that assumption. Class 4 is the general-purpose commercial grade; Class 3 and Class 0 are precision grades used where running accuracy and controlled setting matter, such as machine tool spindles, precision gearboxes and instrument drives. The specific numeric bore, O.D., width and runout tolerance bands for each class are published inside ANSI/ABMA Std 19.2 and Timken’s engineering manual rather than on open product pages, so we are not going to quote numbers we cannot cite. What we can say plainly is the ranking above, and that a Class 3 cone is a precision part and should be handled and installed as one.

Decoding the designation

In Timken’s inch system the basic number identifies the cone (559), and a suffix following the basic number normally identifies the precision class — for example 559-2 is Class 2 and 559#3 or 559-3 is Class 3. There is no published Timken cone suffix “-W”. We searched Timken’s own catalog data and the major distributor databases and could not find any definition for a “-W” cone suffix. The most likely explanation is that the marking on the carton is a mis-transcription of a class or assembly suffix. We are deliberately not publishing an invented meaning for it. If the exact suffix matters for your application, ask us for a photo of the carton end label and confirm the marking before ordering. We have kept 559-W and 559W as searchable cross-references because that is what is printed on the box.

Fitting notes

Cones are an interference fit on the shaft and should be driven or pressed against the large end face using a tool that bears on the cone backface, never on the rollers or cage. Respect the maximum shaft fillet radius of 0.14 in / 3.5 mm and the backing shoulder diameters (da 72 mm, db 78 mm) — a fillet larger than 0.14 in will hold the cone off its shoulder and destroy the setting. After assembly the set must be brought to the endplay or preload the equipment maker specifies; taper sets are not “install and go” like a sealed ball bearing.

Do not mix production lots within a matched assembly:
Cones, roller-and-cage sets and cups from different production lots should not be intermixed inside a bearing that was supplied as a matched or controlled-setting assembly. Roller diameter and cage pocket geometry are held within a lot to produce a specific setting, and swapping members across lots can shift the assembly width enough to change endplay measurably. Replace the cone as a complete unit as supplied, and do not attempt to transplant rollers between cones.

Interchange guidance

The 559 cone basic number is an industry-standard inch taper number and is produced by multiple manufacturers to the same envelope. Search forms include 559, 559W, 559-W, 559 W, and the 559/552A and 559/552 set designations, plus Timken assembly number 559-99401. Confirm the cup half of the pairing before you order, and confirm precision class if your application is class-sensitive.