Koyo WJ-202612 needle roller and cage assembly, 31.75 x 41.275 x 19.05 mm

These Koyo WJ radial needle roller and cage assemblies are single-row, inch series assemblies with a complement of needle rollers held in a steel cage and no inner or outer ring. The minimal cross-section gives maximum load-carrying capability within the smallest envelope. The steel cage retains the needle rollers both inward and outward, and accurate guidance of the rollers by the cage bars allows operation at high speeds.

The shaft and the housing act as the inner and outer raceways, so they must have the correct geometric and metallurgical characteristics to realise the full bearing load rating and life. WJ assemblies are heavy-duty compared with WJC assemblies, because of the nature of the roller diameter. The needle rollers are relieved-end rollers of through-hardened, ground and lapped high carbon chrome steel, and within any one assembly they are made to a single diameter grade with a total diameter tolerance of 0.003 mm (0.0001 in).

The range has 24 sizes with roller complement bore diameters from 19.05 to 76.2 mm. Koyo bearings are made by JTEKT Corporation.

Where this product is used

• Automotive and truck transmissions
• Agricultural and construction equipment
• Two-cycle engines
• Pumps and compressors

Features

• Needle roller and cage assembly with no inner or outer ring: unitised design that simplifies handling and installation and allows increased lube flow
• Steel cage retains the needle rollers inward and outward; cage bars guide the rollers accurately for operation at high speeds
• Relieved-end needle rollers, through-hardened, ground and lapped for diameter and roundness
• Basic dynamic load rating C 26.8 to 83.2 kN and basic static load rating C0 37.1 to 173 kN
• Grease lubrication speed rating 3,600 to 16,000 min-1 and oil lubrication 5,600 to 24,000 min-1
• Shaft and housing mounting dimensions listed for each size: shaft ISO h5, housing ISO G6

Key specifications

Available sizes

Selecting the right option

Choose the size from the shaft (the roller complement bore diameter Fw), the housing bore (the roller complement outside diameter Ew) and the cage width Bc. The WJ designation codes these in sixteenths of an inch: for example WJ-202612 is 20/16 in (1 1/4 in) Fw, 26/16 in Ew and 12/16 in Bc.

Load ratings are based on a minimum raceway hardness of 58 HRC or equivalent.

Fitting and use

Because the shaft and housing are the raceways, they should be 58 HRC or equivalent. The suggested mounting dimensions in the variant specification give a shaft tolerance of ISO h5 and a housing bore tolerance of ISO G6, which provide correct running clearance for most applications. The housing needs enough cross-section to hold its roundness and running clearance under load.

Locate the assembly axially with shoulders or other suitable means, and harden the end locating surfaces to minimise wear. Minimum axial clearance should be 0.203 mm (0.008 in), and fillets next to a WJ assembly must not exceed 0.762 mm (0.03 in) radius.

Oil is the preferred lubricant for most applications, and in critical high-speed applications ample oil flow must be provided.

Related products

Also available from Koyo: the Koyo HK drawn cup needle roller bearing range and the Koyo B series full complement drawn cup bearing range.