TORRINGTONHJ-14817848/IR-12814848Heavy Duty Cylindrical Needle Roller Bearing with Matched Inner Ring, 8.000 x 11.125 x 3.000 in, 145,000 lbf Dynamic Radial, MS 51961

Product Description

What this part is

This is an HJ-series heavy duty single row cylindrical roller bearing — a full-complement roller-and-cage assembly running inside its own outer ring — supplied here together with the matching IR-series hardened and ground inner ring that provides the inner raceway. Assembled, the set fits an 8.000 in shaft in an 11.125 in housing bore and is 3.000 in wide. Timken lists an alternate designation of 6673M for the HJ component, and the bearing meets Military Standard MS 51961.

Decoding the designation

Torrington encodes dimensions in sixteenths of an inch, read three digits at a time. For the HJ-14817848: 148/16 = 9.250 in, which is the roller assembly bore Fw — the diameter the rollers actually run on; 178/16 = 11.125 in outside diameter; 48/16 = 3.000 in width. For the IR-12814848 inner ring: 128/16 = 8.000 in bore, 148/16 = 9.250 in outside diameter, 48/16 = 3.000 in width.

Notice that the inner ring’s 9.250 in outside diameter is exactly the HJ’s Fw. That is the arithmetic proof that these two components are a matched pair rather than a hopeful pairing, and it means the assembled unit is 8.000 in shaft x 11.125 in housing bore x 3.000 in wide — which confirms the 8 x 11-1/8 x 3 in figures the listing has always carried.

Why the inner ring exists

An HJ bearing does not need an inner ring. If the shaft it runs on is hardened and ground to raceway quality, the rollers can bear directly on the shaft, which saves radial space and reduces part count. The catch is what happens when the raceway wears: on a direct-mounted design the shaft itself is the consumable, and replacing a large shaft is a rebuild, not a repair.

Where the shaft cannot be hardened, is already worn, or simply has to stay field-repairable, the IR inner ring becomes a replaceable sacrificial raceway pressed onto the shaft. Rings get replaced; shafts do not. That is the practical reason to buy the HJ and IR together, and it is worth understanding before deciding whether you need the ring at all.

Published ratings and mounting data

Dynamic radial load rating C₁ (1 million revolutions, ISO method): 599,000 N / 145,000 lbfStatic radial load rating C₀: 1,350,000 N / 326,000 lbfThermal speed rating: 1,300 rpm oil, 1,200 rpm greaseGeometry factor Cg: 0.1885 (quoted for the bearing without inner ring)Housing shoulder diameter Da: 266.70 mm / 10.500 inMaximum housing fillet radius (LF/RF, OD side): 0.16 in / 4.060 mmWeight: approx. 22.10 lbStandard: Military Standard MS 51961

What these specs mean in practice

The load numbers are the reason this bearing exists. A dynamic radial rating of 145,000 lbf and a static rating of 326,000 lbf in a 3.000 in width is well beyond what a ball bearing of the same envelope could carry, because a full complement of cylindrical rollers puts line contact rather than point contact against the raceway. The trade is speed and axial capability: the thermal speed rating tops out at 1,300 rpm on oil and 1,200 rpm on grease, and a cylindrical roller bearing of this type locates radially only — axial location has to come from somewhere else in the assembly.

Cg 0.1885 is Timken’s geometry factor for life and rating calculations; note their qualification that it is quoted for the bearing without the inner ring, so if you are running the assembly with the IR fitted, use it with that caveat in mind. Da 266.70 mm is the housing shoulder diameter the outer ring is designed to seat against, and the 0.16 in maximum fillet is what the outer ring corner will clear.

Fitting notes

Timken publishes both a clearance and a tight transition fit for this bearing. Clearance fit: 234.920–234.950 mm (9.2488–9.2500 in) at the roller assembly bore and 282.575–282.626 mm (11.125–11.1270 in) at the outside diameter. Tight transition fit: 234.869–234.899 mm and 282.509–282.560 mm respectively.

Timken’s guidance on choosing between them: the clearance fit is suggested for the outer ring where the housing is stationary relative to the load, and the tight transition fit is suggested where the housing rotates relative to the load. For oscillating applications Timken asks that you consult them directly, because of low radial-clearance concerns in that duty. One assembly detail that is easy to miss: the unmarked end of the outer ring should be assembled against the housing shoulder, which is what clears the maximum allowed housing fillet.

Quantity and configuration

One set is in stock, and the set is the HJ-14817848 roller assembly and the IR-12814848 inner ring together. This matters because the two are normally catalogued and sold as separate items, and a buyer working from a part number alone has no way of knowing which they are getting. Here you get both. Central Surplus also stocks the IR-12814848 inner ring on its own as a separate SKU, which is the right purchase if the roller assembly and outer ring are still serviceable and only the worn raceway needs replacing.

Interchange guidance

Search terms and equivalent designations: HJ14817848, HJ 148 178 48, HJ-14817848, 6673M (Timken alternate), IR12814848, IR-12814848. Torrington needle roller bearings are now catalogued under The Timken Company following Timken’s acquisition of the Torrington line, so a search on the Torrington name alone will miss current production and current datasheets — look under Timken for anything you need to verify against a live catalogue.