Timken3879/3820ATapered Roller Bearing Assembly, Cone & Cup – 1.5748 in Bore, 3.3750 in OD, 1.1875 in Assembled Width, Open, Pressed Steel Cage, K Factor 1.45

Product Description

What this part is

Timken 3879/3820 inch tapered roller bearing, single row, supplied as a matched cone and cup. Manufacturer: Timken. Manufacturer Part Number: 3879/3820A. Cone Part Number: 3879. Cup Part Number: 3820. Base Number: 3879/3820. Series: 3800. Bearing Type: Tapered Roller Bearing Assembly, TS single row. Number of Rows: 1. Rolling Elements: Tapered Rollers. Design Units: Inch. Bore: 1.5748 in (40 mm). Outside Diameter: 3.3750 in (85.725 mm). Assembled Width: 1.1875 in (30.163 mm). Inner Ring Width: 1.1875 in (30.163 mm). Outer Ring Width: 0.9375 in (23.813 mm). Bore Type: Straight. Closure Type: Open. Cage Type: Pressed steel. Cage Material: Steel. Bearing Material: Case-Carburized Steel. Precision Class: Not specified. Item Weight: 1.8 lb (0.8 kg). Unit Quantity: 2 Pcs.

Decoding the designation

Timken names this bearing by its cone and cup pair: cone 3879 against cup 3820, both in the 3800 inch series. The 1.5748 in bore is the inch expression of a round 40 mm, which is why this number appears in both inch and metric shaft schedules. Searchable forms of the number are 3879/3820A, 3879 3820-A, 3879/3820, 3879 / 3820 and 3879-3820.

What these specs mean in practice

Dynamic Radial Load Rating C1, ISO method at 1 million revolutions: 27,900 lbf (124,000 N). Dynamic Radial Load Rating C90, Timken method at 90 million revolutions: 7,240 lbf (32,200 N). Dynamic Axial Rating Ca90: 4,980 lbf (22,200 N). Static Radial Load Rating C0: 33,200 lbf (148,000 N). e Factor: 0.40. K Factor: 1.45. Y Factor: 1.49. G1 Factor: 37.8. G2 Factor: 13.5. Geometry Factor Cg: 0.0873. These are the ratings for the complete single-row assembly. The K factor of 1.45 is a steep raceway angle for this envelope, which weights a larger share of the capacity toward thrust, and the Y factor of 1.49 converts a thrust component into an equivalent radial load once the axial-to-radial ratio passes the e value of 0.40. C1 and C90 are two different life bases for the same bearing and are not interchangeable in a calculation. Harmonization Code: 8482.20.00.

Mounting dimensions

Effective Center Location: −0.32 in (−8.1 mm), which places the effective centre inside the cone backface. Maximum Shaft Fillet Radius: 0.030 in (0.8 mm). Maximum Housing Fillet Radius: 0.130 in (3.30 mm). Shaft Backing Shoulder Diameter, frontface (da): 1.97 in (50 mm). Shaft Backing Shoulder Diameter, backface (db): 2.01 in (51 mm). Housing Backing Shoulder Diameter, frontface (Da): 3.23 in (82.00 mm). Housing Backing Shoulder Diameter, backface (Db): 2.87 in (72.90 mm). Cage Location relative to the backface (Aa): 0.04 in (1 mm). Cage Location relative to the frontface (Ab): 0.11 in (2.8 mm). These figures decide whether a given shaft step, housing step and fillet will clear the bearing corners and the cage.

Quantity and configuration

Unit Quantity: 2 Pcs. One cone assembly — the inner ring with its tapered roller set and pressed steel cage — and one matching cup, the 3820 outer ring. Together they make one complete single-row tapered roller bearing. The 15/16 in figure carried in the listing title is the cup width of 0.9375 in; the assembled width across the mounted pair is 1.1875 in.

Cone and cup mating

Cone 3879 runs against cup 3820, and Timken designates the assembly by that pair rather than by a separate assembly number. The same cone also runs against the 3821 cup, and against the flanged 3820-B cup in a TSF arrangement. A B suffix on a cup marks a flanged cup, which locates axially in a through-bored housing. The cup carries no bore, no cage and no roller set: it is the outer race alone, and its raceway angle is cut to match the 3879 cone.

Interchange guidance

Cross-Reference 1: SKF 3879/3820. Cross-Reference 2: NTN 4T-3879/3820. Cross-Reference 3: Bower 3879/3820. All three sit on the same 1.5748 x 3.3750 x 1.1875 in envelope on the same raceway geometry. The NTN 4T prefix denotes the cone half in that maker’s scheme.