KoyoNJ317C3Single-Row Cylindrical Roller Bearing 85 x 180 x 41 mm, NJ Design, Straight Bore, C3 Clearance, Locates in One Direction

Product Description

What this part is

A Koyo NJ317 C3 single-row cylindrical roller bearing, 85 mm bore x 180 mm outside diameter x 41 mm wide, straight bore, with greater-than-normal radial internal clearance. One row of cylindrical rollers carries 225 kN dynamic and 247 kN static radial load in a 47.5 mm cross-section — roughly three times the radial capacity of a 6317 ball bearing in the same envelope. This is a gearbox, electric motor and industrial drive bearing.

Decoding the designation

NJ — single row with two ribs on the outer ring and one rib on the inner ring. The bearing locates the shaft axially in one direction.
3 — ISO dimension series 3 (heavy section).
17 — 85 mm bore.
C3 — radial internal clearance greater than normal.
E / EM / ECM — uprated-capacity internal designs offered in this size by various makers; M denotes a machined brass cage and FY is a Koyo cage and finish code. These appear as searchable equivalents in this listing.

Axial location and the NJ, NU, N and NUP designs:
The rib arrangement is what a cylindrical roller bearing is selected on, and the four common designs are not interchangeable:

NJ — one inner-ring rib. Takes light axial load and locates the shaft in one direction. This bearing.
NUP — two inner-ring ribs, one of them a loose flange ring. Locates the shaft in both directions.
NU and N — no inner-ring rib and no outer-ring rib respectively. These are non-locating: they allow the shaft to move axially through the bearing.

An NJ317 fitted where an NU317 was is a bearing with more axial constraint than the design assumed; an NU317 fitted where an NJ317 was leaves the shaft free to travel axially in that position. The two carry the same radial rating and the same 85 x 180 x 41 mm envelope, so the rib arrangement is the specification that matters here.

What these specs mean in practice

C3 clearance suits a tight interference fit on the shaft, a heavy press fit, or a hot-running application — the extra cold clearance is consumed as the inner ring expands, leaving normal running clearance at temperature. Line contact between roller and raceway is what buys the load capacity: a cylindrical roller spreads its load along a line rather than a point, which is why this bearing rates three times a ball bearing of the same size, at the cost of a lower speed ceiling and no meaningful thrust capacity.

Published ratings and mounting data

Bore d: 85 mm (3.3465 in) — Outside diameter D: 180 mm (7.0866 in) — Width B: 41 mm (1.6142 in)
Basic dynamic load rating C: 225 kN
Basic static load rating C0: 247 kN
Limiting speed, grease: 3 300 rpm — oil: 4 500 rpm
Rows: 1 — rolling element: cylindrical roller
Bore form: straight cylindrical
Radial internal clearance: C3, greater than normal
Rib arrangement: two outer-ring ribs, one inner-ring rib (NJ)
Closure: open, no seals or shields
Material: through-hardened bearing steel
Mass: approx. 4.67 kg (10.3 lb)

Quantity and configuration

Sold as 1 Pc — one complete bearing: the ribbed outer ring, and the inner ring with its single rib carrying the roller and cage assembly. The bearing is separable into those two parts.

Fitting notes

The inner ring goes on with an interference fit, heated or pressed square to the shaft shoulder, with the ribbed inner-ring face oriented to take thrust in the direction the arrangement requires — that orientation is what makes the NJ design do its job. The outer ring seats in the housing bore to the fit the drawing calls for. Because the rings separate, they can be mounted independently, and each ring is marked so the roller assembly returns to its original outer ring.

Interchange guidance

Same-specification equivalents at 85 x 180 x 41 mm, NJ rib arrangement, C3 clearance: SKF NJ 317 ECJ/C3, FAG NJ317-E-XL-M1-C3, NSK NJ317C3, NTN NJ317C3, Nachi NJ317C3, Timken NJ317. Related sizes, not substitutes: NU317, N317 and NUP317 share this envelope and radial rating but have different rib arrangements and therefore different axial behaviour; NJ317E and NJ317ECM are uprated internal designs with higher load ratings; a CN-clearance NJ317 runs a different fit-up from this C3 unit; and the double-row NN3017 or NNU4917 mount entirely differently.