Timken780/774D/X1STwo-Row TDO Tapered Roller Bearing Assembly – 4.0000 in Straight Bore, 7.1250 in Outside Diameter, 4.1250 in Width, Double Cup with Two Cones and a Ground Cone Spacer

Product Description

What this part is

Timken 780/774D/X1S two-row TDO tapered roller bearing assembly, 4.0000 in bore, 7.1250 in outside diameter, 4.1250 in overall width. The assembly comprises two 780 cones, one 774D double cup and one X1S-780 cone spacer, supplied together as a matched, factory-set unit. Timken assembly numbers 780-90050 and 780-90049.

Decoding the designation

780 is the cone number and 774 the cup number in the 775 imperial series. The D on 774D marks a one-piece double cup carrying two raceways, so it takes two cones. X1S is the Timken prefix for a cone spacer, ground to width to set the assembly. A –90xxx number such as 90050 or 90049 designates a complete assembly rather than a single component.

What these specs mean in practice

TDO stands for two single rows in a double outer race. The rows sit back to back inside one cup, so the contact lines diverge and the effective load centres are spread wide apart, which gives the assembly high moment stiffness for its width and the ability to take thrust in both directions. Basic dynamic capacity is 498 kN (112,000 lbf) and basic static capacity 765 kN (172,000 lbf). Because the cone spacer is ground to this particular cup and cone set, the internal setting is fixed at the factory and repeats on assembly.

Quantity and configuration

One complete assembly: two cones, one double cup, one ground cone spacer. Straight bore, open, case-hardened bearing steel with stamped steel cages. Mass approximately 23.5 lb (10.6 kg).

Fitting notes

The two cones seat on the shaft on an interference fit with the ground spacer between them, and the double cup is a light interference or transition fit in the housing bore, clamped square by an end cap or retainer. The factory setting is preserved by keeping the original spacer with its own cup and cones. Operating temperature range is –54 to 120 °C.

Interchange guidance

The 780/774D combination is published to the same ABMA inch designation by SKF, NTN, FAG, Koyo and the legacy Bower catalogue. Within the same 774D double cup, a 775 cone gives a 3.5000 in bore, a 778 a 3.6250 in bore, a 782 a 4.1250 in bore and a 783 a 3.9370 in bore — all related sizes rather than substitutions for a 4.0000 in bore.