Timken48190-3Class 3 Precision Tapered Roller Bearing Cone Only, 4.2500 in Bore x 1.3750 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 tapered rollers, and the cage that retains them, supplied as one non-separable assembly. It is the Timken 48190 cone in Class 3 precision, 4.2500 in (107.95 mm) bore by 1.3750 in (34.925 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 48120, confirmed on Timken’s own catalogue entry for the 48190, 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. Selling them apart is normal — they mount in different members and wear at different rates — but a buyer expecting a complete bearing and receiving a bare cone is the single most common and most expensive mistake in this product family. If you need the whole bearing, order a 48120 cup as well.

Decoding the designation

48190 — Timken inch-series cone part number. The cone number is what selects the bore; 48190 gives the 4.2500 in shaft fit.48120 — the mating cup number in the same series. Together they form the 48190 / 48120 single-row assembly.-3 (also written *3 or #3) — this is a Timken precision class suffix, not a variant or a revision. It denotes Class 3. See below for what it buys.

What Class 3 precision actually buys you

Timken’s inch tapered roller precision ladder runs from standard class through Class 3 and on to Class 0 and Class 00, each step tightening the tolerances. Class 3 is the first genuine precision step above standard, and Class 00 is tighter still — so if your drawing calls for Class 00, this Class 3 cone is not a substitute.

What tightens at Class 3 is closer control on the bore diameter and on the raceway geometry, and tighter running accuracy: less radial and axial runout as the bearing turns. That matters in positions where the bearing sets the position of something rather than merely carrying it — machine-tool spindles, precision gearboxes, index and rotary tables, boring and grinding heads, test and measuring equipment. Runout at the bearing is transferred directly into the gear mesh or the workpiece, so a few ten-thousandths at the raceway becomes a visible error at the tool.

It is also a real price differentiator rather than a marketing suffix. A Class 3 cone takes extra grinding and gauging to produce and costs meaningfully more than a standard-class 48190, and a buyer whose drawing specifies the class cannot substitute the standard part. Equally, if the position is an ordinary industrial one, a standard 48190 is the sensible buy — there is no reason to pay for accuracy you will not use.

Published ratings and mounting data

Load ratings below are Timken’s own published figures. They describe the complete 48190 / 48120 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): 4.2500 in / 107.95 mmInner ring width (B): 1.3750 in / 34.925 mmPrecision class: Class 3Mating cup: 48120Dynamic radial load rating C1 (1 million revolutions, ISO method): 43,200 lbf / 192,000 NDynamic radial load rating C90 (90 million revolutions, Timken method): 11,200 lbf / 49,800 NDynamic axial rating Ca90: 9,680 lbf / 43,100 NStatic radial load rating C0: 69,200 lbf / 308,000 NK factor: 1.16Effective centre location (a): 0.15 in / 3.8 mmMaximum shaft fillet radius cleared: 0.14 in / 3.560 mmShaft backing shoulder diameter, frontface (da): 4.57 in / 116 mmShaft backing shoulder diameter, backface (db): 4.8 in / 122 mmCage location relative to backface (Aa): 0.09 in / 2.3 mmCage location relative to frontface (Ab): 0.07 in / 1.8 mmG1 factor 180, G2 factor 44.7, geometry factor Cg 0.156Cone weight: 5.2 lb / 2.3 kg

What these specs mean in practice

The K factor of 1.16 tells you the duty this bearing was drawn for. K is the ratio of radial to thrust capability, fixed by the cup angle: the lower the K, the steeper the angle and the more thrust the bearing carries for a given radial load. At 1.16 the 48190 / 48120 is a comparatively steep-angle bearing — its published Ca90 of 9,680 lbf is within striking distance of its C90 of 11,200 lbf, so it will take serious axial load alongside the radial reaction. That is the profile of a bevel or helical gear shaft, or a spindle taking cutting thrust, rather than a plain radial support position.

C1 and C90 describe the same bearing at two different life bases — C1 (43,200 lbf) at one million revolutions on the ISO method, C90 (11,200 lbf) at ninety million revolutions on Timken’s method. They are not competing claims, and comparing one maker’s C1 against another’s C90 will produce a nonsense answer. G1, G2 and Cg are the constants for Timken’s own life arithmetic, with Cg feeding the lubrication life adjustment factor a3l; they are published here because distributor listings almost never carry them.

Quantity and configuration

One cone in stock, priced and sold as a single piece. The condition note records that this cone came out of a factory-new set and is factory-packed with grease — in other words, a new set was split and this is the surviving cone half, which is exactly why the cup is not here. It is unused, not a pull.

Bear in mind that single-row tapered roller bearings normally work in opposed pairs, because one row can only resist thrust in one direction. A typical shaft therefore needs two cones and two cups. With one cone available, this suits a single-position replacement or a spare rather than a full two-position rebuild — and for a Class 3 part, having the matching class on hand as a spare is often the whole point.

Fitting notes

The cone is an interference fit on the shaft. Press it on square with the load taken on the cone backface only — never through the rollers or the cage. A blow that passes through the roller set will brinell the raceway and destroy the running accuracy you paid the Class 3 premium for, which defeats the entire purpose of buying it. Respect the 0.14 in maximum shaft fillet radius at the shoulder and keep the backing shoulder within the published da / db window so the cone seats flat and 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 both bearing life and spindle accuracy. On a precision position set it to the machine builder’s figure with a dial indicator or a torque-and-rotation check rather than by feel, and do not reuse an old shim stack against a new cone — an unworn raceway changes the stack-up.

Interchange guidance

48190 is an industry-standard inch cone designation rather than a Timken-proprietary code, and cones to this number are produced by several manufacturers, so a same-number cone from another maker is dimensionally interchangeable in the standard class. The precision class does not interchange: a standard-class 48190 fits the same envelope but will not deliver Class 3 running accuracy, and a Class 00 requirement is not met by a Class 3 part. If the drawing specifies a class, match the class.

Searchable forms: 48190-3, 48190 *3, 48190#3, 48190 #3, 48190*3, 48190 Class 3, and the unsuffixed standard-class 48190, plus 48-190, 48 190 and K-48190. Mating cup: 48120, 48-120, 48 120. Complete assembly designations: 48190/48120, 48190-48120, 48190/48120-3.

Central Surplus also stocks other Timken inch-series cups and cones, including Class 00 precision cones and large-bore cup references; if you need a matched-class pair it is worth checking what else is on the shelf before ordering the cup elsewhere.