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Two-row tapered roller bearing set, 4 in bore, 7-1/8 in OD. Two NA780 cones with one 774D double cup in TDO form, case carburized steel.
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| MFR / Brand | Timken |
|---|---|
| MPN | NA780/774D |
| Model | NA 780 / 774 D |
| Bearing Type | Tapered roller bearing cones and double cup (TDO components), Open - no seal |
| ID | 4.0000 in |
| OD | 7.1250 in |
| Width | 4.2500 in |
| Series | 700 |
|---|---|
| Condition | New – Open box |
| Material | Case Carburized Steel |
| Base Number | 780/774D |
| Industry Terms | TDO bearing, double cup tapered roller, two row taper bearing, mill bearing, cone and cup set |
| Common Misspellings | Timkin, Timpken, NA 780 774 D, 774DD |
| Application Types | Rolling mill work rolls, wheel ends, gearbox and conveyor shafts, heavy industrial shafting |
| Condition Note | Made In USA, (2) NA-780 (1) 774-D, New Old Stock, Stained |
| Bore Shaft Size | 4.0000 in (101.60 mm) |
| Mpn Variants | NA780/774D, NA780 774D, NA-780 774-D, NA780, 774D, 774-D, 780/774D |
| Manufacturer Status | Timken inch tapered series, current |
| Arrangement Configuration | TDO - tapered double outer, two cones on one double cup |
| Precision Class | Timken Class 2 (standard) |
| Min Temp | -54 °C |
| Cage Type | Stamped |
| Dynamic Load Rating | 179 kN / 40200 lbf |
| Static Load Rating | 320 kN / 71900 lbf |
| Precision Rating | Timken Class 2 (standard precision) |
| Rolling Elements | Tapered Rollers |
| Max Temp | 120 °C |
| Item Weight | 18.5 lbs |
| Cage Material | Steel |
| Number Of Rows | 2 |
| Bore Type | Straight |
| Snap Ring Included | Without Snap Ring |
| Harmonization Code | 8482.20.00 |
| Design Units | Inch |
| Part Number | NA780 / 774D |
| Cross Reference 1 | Timken 780 (related, single-row service cone, same raceway) |
|---|---|
| Cross Reference 2 | Timken 774D (double cup, component of this set) |
| Cross Reference 3 | Timken 782/774D (related size, 4.1250 in cone bore, same double cup) |
| Cross Reference 4 | Timken 783/774D (related size, 3.9370 in cone bore, same double cup) |
Timken two-row tapered roller bearing components in the 780/774 inch series: two NA780 cones and one 774D double cup. Cone bore 4.0000 in (101.60 mm), cup outside diameter 7.1250 in (180.975 mm). Case carburized alloy steel, stamped steel cages, tapered rollers.
780 is the cone number and 774 the cup number in Timken’s inch tapered series. The NA prefix marks a cone furnished for two-row and TDO service, ground to the matched width tolerances that two-row mounting needs. The D suffix on the cup number identifies a one-piece double cup with two raceways, so a single 774D seats two cones back to back.
Three pieces: two NA780 cones and one 774D double cup. Together they form the tapered double outer, or TDO, arrangement — the two cones facing outward against a single common cup.
A TDO arrangement carries thrust in both directions and takes overhung and moment loading, which is why it appears on rolling mill work rolls, wheel ends and screw conveyor shafts. Because both raceways are cut in one cup, the outer clearance is fixed at manufacture and setting happens on the cone side. Case carburized rings give a tough core under a hard raceway, favouring shock loading over through-hardened steel.
The cones mount on a straight cylindrical shaft seat and the double cup presses into a single bore in the housing. Bearing setting is made by adjusting the cone spacing against the shaft shoulder or a spacer, and the cup is located axially by the housing shoulder and cap. Rated limiting speed 3800 rpm.
The plain 780 cone shares the raceway and rollers and is the single-row service version of the same cone. The 782/774D and 783/774D sets use the same 774D double cup on different cone bores — 4.1250 in and 3.9370 in respectively — making them related sizes on a common cup rather than interchanges. The 780/772 set uses the same cone against a single cup for one-direction single-row service.
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