TimkenLL639249Tapered Roller Bearing Cone Only, 7.7500 in Bore x 0.9062 in Inner Ring Width, Inch Series – Mating Cup Not Included

Product Description

What this part is

This is the cone half of a single-row tapered roller bearing — the inner ring with its ground tapered raceway, the full complement of tapered rollers, and the cage that retains them, supplied as one non-separable assembly. It is the Timken LL639249 cone from the LL639200 inch series, with a 7.7500 in (196.850 mm) bore and a 0.9062 in (23.017 mm) inner ring width. The cone is the half that presses onto the shaft.

What is and is not included

This listing is the cone only. The mating cup is not included. The cup for this cone is the Timken LL639210, and without it you do not have a working bearing. A tapered roller bearing is two separately numbered halves: the cup (outer ring) presses into the housing, the cone (inner ring plus rollers plus cage) presses onto the shaft. They are sold apart because they wear at different rates and mount in different members, so a cone-only replacement is entirely normal practice — but if you are building up a complete bearing you must buy an LL639210 cup as well. Getting this wrong is the most common and most expensive mistake in this product family, so it is worth reading twice.

Decoding the designation

LL639249 — Timken cone part number. The LL prefix denotes a Timken inch (imperial) series. Within Timken inch numbering the cone and cup carry separate numbers in a common series; here the LL639249 cone pairs with the LL639210 cup.The cone number is what selects the bore. LL639249 gives the 7.7500 in shaft fit.“LL-639249-XX” appears in the Central Surplus source data. The -XX is not a Timken suffix and carries no Timken meaning — it is a distributor / internal notation. It is kept below as a cross-reference so buyers searching that string find the part, but the Timken designation is simply LL639249.No precision-class suffix is present on this cone, so it is a standard-class Timken tapered roller bearing cone rather than a Class 3 or Class 00 precision variant.

Published ratings and mounting data

Load ratings below are Timken’s own published figures. They describe the complete LL639249 / LL639210 single-row assembly, not the cone in isolation — a bare cone has no rating of its own, because capacity is a property of the roller set running between both raceways. Bore, inner ring width, weight and shaft abutment figures are cone-specific.

Cone bore (d): 7.7500 in / 196.850 mmInner ring width (B): 0.9062 in / 23.017 mmMating cup: LL639210Dynamic radial load rating C1 (1 million revolutions, ISO method): 38,800 lbf / 172,000 NDynamic radial load rating C90 (90 million revolutions, Timken method): 10,100 lbf / 44,700 NDynamic axial rating Ca90: 7,190 lbf / 32,000 NStatic radial load rating C0: 76,300 lbf / 340,000 NK factor: 1.4Effective centre location (a): 0.69 in / 17.5 mmMaximum shaft fillet radius cleared: 0.06 in / 1.520 mmShaft backing shoulder diameter, frontface (da): 7.99 in / 203 mmShaft backing shoulder diameter, backface (db): 8.07 in / 205 mmCage location relative to backface (Aa): 0.04 in / 1 mmCage location relative to frontface (Ab): 0.14 in / 3.6 mmG1 factor 443, G2 factor 230.2, geometry factor Cg 0.133Cone weight: 4.6 lb / 2.1 kg

What these specs mean in practice

The K factor of 1.4 is the figure that tells you what this bearing is for. K is the ratio of radial to thrust capability, set by the cup angle: a low K means a steeper angle and a bearing that carries proportionally more thrust for a given radial load. At 1.4 the LL639200 series sits toward the thrust-capable end of the tapered roller range, which suits it to shaft positions where a helical or bevel gear set is throwing significant axial load along with the radial reaction — large gearbox shafts, pinion positions, heavy machine spindles.

The distinction between C1 and C90 matters when you compare this bearing against another maker’s catalogue. C1 (38,800 lbf) is the ISO figure at one million revolutions; C90 (10,100 lbf) is Timken’s own figure at ninety million revolutions. They are not competing numbers — they are the same bearing described at two different life bases. Compare like with like or you will conclude one bearing is four times stronger than an identical one.

G1, G2 and Cg are the constants Timken publishes for its own life-adjustment arithmetic; Cg feeds the lubrication life adjustment factor a3l. They are of no use unless you are running the Timken method, but they are published here because they are almost never carried by distributor listings and an engineer doing a real life calculation needs them.

Quantity and configuration

Priced and sold per single cone. Eight are in stock, so a multi-position rebuild can be filled from one source. Single-row tapered roller bearings are normally mounted in opposed pairs — two bearings facing each other, in a back-to-back or face-to-face arrangement — because one row can only take thrust in one direction. Count your positions before ordering, and remember each position also needs its own cup.

Fitting notes

The cone is an interference fit on the shaft. Press it on square, bearing on the cone backface, never on the rollers or the cage; a load path through the roller set will brinell the raceway and the bearing will be audibly rough from the first hour of service. Respect the 0.06 in maximum shaft fillet radius at the shoulder or the cone will not seat flat, and keep the shaft backing shoulder within the published da / db window so the cone is properly supported.

A tapered roller bearing has no built-in internal clearance. The operating clearance or preload is created at assembly by how far the cone is drawn up against the cup, and that setting is the single largest determinant of service life in this bearing class. If you are fitting a new cone against an existing cup, re-set endplay to the machine builder’s specification rather than reusing the old shim stack — a new cone has an unworn raceway and changes the stack-up.

Interchange guidance

LL639249 is an industry-standard inch designation, not a Timken-proprietary code, and cones to this number are produced by several manufacturers. That means an LL639249 from another maker is dimensionally interchangeable, and it also means a buyer searching any maker’s version of the number is looking at the right part here. Searchable forms: LL639249, LL-639249, LL 639249, LL639249XX, LL-639249-XX, L639249. Mating cup: LL639210, LL-639210, LL 639210. Complete assembly designations: LL639249/LL639210, LL639249-LL639210.

Central Surplus also stocks other large-bore Timken inch-series cups and cones, including the M241500 series; if you are rebuilding a heavy gearbox or final drive it is worth checking the adjacent sizes.