TimkenRAK2-15/16Two-Bolt Pillow Block Ball Bearing Unit, 2-15/16 in Bore, Eccentric Locking Collar, Cast Iron Housing, Non-Expansion

Product Description

What this part is

A two-bolt base pillow block ball bearing unit for a 2-15/16 in shaft, from Timken’s Fafnir-legacy RA insert range. The insert is a wide inner ring ball bearing with contact seals, secured to the shaft by an eccentric locking collar, mounted in a nickel-plated cast iron housing.

Correcting the source data — two errors

The previous listing called this a flange mount bearing. It is a pillow block. In Fafnir nomenclature RA denotes the wide-inner-ring insert and the K denotes a pillow block housing; Fafnir’s four-bolt flange codes are RCJ, RCJO and TCJ, and the two-bolt flange is RCJT. There is no flange in an RAK number.

This is the error class that generates automatic returns: a buyer needing to bolt a bearing to a vertical face would receive a unit that bolts to a horizontal base. Title and copy corrected.

Second, the locking method. The natural assumption on a Fafnir RA insert is a setscrew, and that assumption is wrong here — Timken catalogues RAK 2-15/16 under eccentric locking collar units. That distinction changes how you fit it and is covered below.

Why an eccentric collar rather than setscrews

An eccentric collar locks by interference rather than by biting into the shaft. The collar has an eccentric counterbore that matches an eccentric register on the insert’s extended inner ring; you slip the collar on, turn it a quarter turn in the direction of shaft rotation, and the two eccentrics cam against each other to grip the shaft. A single setscrew in the collar then holds it in position.

What that buys you: no dimples punched into the shaft, so the shaft survives repeated bearing changes and remains reusable; a concentric grip that does not push the inner ring off-centre the way an unevenly tightened setscrew pair can; and reliable holding under load reversal. What it costs you: the collar only grips properly when turned in the direction of shaft rotation, so it is direction-dependent. Fit it the wrong way round and normal running will progressively loosen it. That single point is the most common eccentric-collar failure and it is entirely avoidable.

Published data

Bore: 2-15/16 inHousing style: two-bolt base pillow block, cast iron, nickel platedLocking: eccentric locking collarSeals: contact sealExpansion: non-expansion (fixed)Base to bore centreline: 3-5/16 inBolt centre to centre: 9-1/2 inOverall L x W x H: 10-1/2 x 3-5/8 x 6-7/16 inDynamic load rating: 14,000 lbStatic load rating: 10,100 lbWeight: 19.9 lb / 9.026 kgMaximum temperature: 250 °F

Being straight about provenance: Timken’s own catalogue page confirms the housing style, locking method, seal type, bore and base-to-centre dimension. The load ratings, the remaining dimensions, the weight and the temperature limit come from a distributor record rather than a Timken-hosted table, so treat those as provisional and ask if you need them certified.

Fitting notes

Because this is a non-expansion unit it locates the shaft axially. On a shaft carried by two or more bearings, only one should be non-expansion; the others must be free to float, or thermal growth will load the bearings against each other. Check that this unit is the intended locating position before you fit it.

Self-aligning inserts of this type tolerate a degree of initial misalignment between the two bearing seats, which is why pillow blocks dominate conveyor, fan and line-shaft work. That tolerance is for static mounting error, not for a permanently misaligned running shaft — a shaft that runs out of line will still destroy the bearing, just more slowly.

Interchange guidance

Cross-references: RAK2-15/16, RAK 2-15/16, RAK2 15/16, RAK-2-15/16, RAK2-15-16, Fafnir RAK2-15/16. Related Fafnir housing styles taking the same insert size: RCJ (four-bolt flange), RCJO, TCJ, RCJT (two-bolt flange), RCJC (cartridge). Obsolescence trail: Fafnir was acquired by Timken, so Fafnir RAK numbers are quoted and supplied by Timken.

Central Surplus also stocks SealMaster, Link-Belt and Dodge mounted units in nearby bore sizes.