KoyoHJ-122012Needle Bearing 3/4″ ID 1-1/4″ OD HJ122012 MS-51961-2 2 Pcs

Product Description

What this is
A pair of Koyo HJ-122012 heavy-duty needle roller bearings in the inch HJ series — 3/4 in bore, 1-1/4 in outside diameter, 3/4 in wide. Machined-ring construction: a hardened, ground outer ring with an integral rib at each end, a full row of needle rollers in a steel cage, and no inner ring. The needles run directly on the shaft, so the shaft journal has to be hardened and ground to the bearing’s specification. Where that is not practical, the matching separate inner ring is IR-081212.

The outer rings are stamped KOYO K USA, HJ-122012 and MS 51961-2, and the cartons confirm it: made in the United States, not Japan. Both boxes are original Koyo, two pieces, one per box.

How the part number breaks down
HJ — the heavy-duty needle roller bearing series: caged, single row, machined outer ring, no inner ring, inch dimensions. Koyo and Torrington use the same designation for the same envelope, so the two are interchangeable.

12 — the bore in sixteenths of an inch: 12/16 = 0.750 in.

20 — the outside diameter in sixteenths: 20/16 = 1.250 in.

12 — the width in sixteenths: 12/16 = 0.750 in.

MS-51961-2 is the government standard part number this bearing is built to, marked on the ring alongside the commercial designation. Also written HJ122012, HJ 122012 and MR-12N.

Published figures

Bore (Fw): 0.750 in / 19.050 mm
Outside diameter: 1.250 in / 31.750 mm
Width: 0.750 in / 19.050 mm
Basic dynamic load rating: 20.7 kN (4,650 lbf)
Basic static load rating: 23.3 kN (5,240 lbf)
Limiting speed: 16,000 rpm grease, 25,000 rpm oil
Rows: 1
Cage: steel
Inner ring: none — matching inner ring is IR-081212
Government designation: MS-51961-2
Quantity in this lot: 2 pieces
Made in U.S.A.