TORRINGTON32SF52Radial Spherical Plain Bearing 3-1/4 x 5-1/8 in, Unsealed Steel-on-Steel, Single-Fractured Outer Ring, MoS2 Coated, Relubricatable Through Either Ring

Product Description

What this part is

A radial spherical plain bearing: two pieces, no rolling elements. The inner ring has a convex spherical outer surface, the outer ring a matching concave bore. That geometry is what gives it very high load capacity for its size and lets it swallow shaft misalignment that would destroy a ball or roller bearing. It is a sliding bearing, so it is built for heavy, slow, oscillating duty rather than continuous rotation at speed.

Decoding 32SF52

32 – the Torrington series number, an approximate bore reference (about 3.2 in).SF – spherical plain, radial type, with a single-fractured outer ring. The outer ring is deliberately split axially in one place so the rings can be assembled without loading slots; a snap ring is supplied to hold the two halves together for handling and installation.52 – the exact bore in sixteenths of an inch. 52/16 = 3.250 in. That is the number to trust when a listing elsewhere has the size wrong.No seal suffix – this is the unsealed version. 32SF52SS has synthetic resin seals and 32SF52TT has reinforced nitrile rubber lip seals. They are dimensionally interchangeable with this bearing but they are different part numbers, and the sealed versions are limited to 212°F (100°C) by the seal material. This one has no such seal limit.

Correcting the source data

Earlier copy for this item described 5-1/8 in as an “overall length” and 3-1/4 in as a “shaft diameter”. To be precise: 3.2500 in (82.55 mm) is the bore, 5.1250 in (130.18 mm) is the outside diameter, and 2.8437 in / 2-27/32 in (72.23 mm) is the inner ring width — not the overall width of the assembly. The outer ring is narrower, at 2-7/16 in (61.91 mm). The inner ring standing proud of the outer ring on both faces is normal and intentional on this bearing type: it is what allows the inner ring to tilt inside the housing.

Construction and why it is built this way

Both rings are through-hardened steel, precision ground, with a steel-on-steel sliding contact. The contacting surfaces are phosphate treated and coated with molybdenum disulphide (MoS2) to cut friction on start-up and during the slow reversals this bearing is designed for. Note that the MoS2 coating reduces the ground radial internal clearance by up to 0.002 in (0.05 mm) — if you are measuring clearance on an uncoated drawing figure, that is where the difference comes from. The SF series carries lubrication holes and grooves in both the inner and the outer ring, so you can relubricate through either the shaft or the housing, whichever is easier to plumb on the machine. Steel-on-steel construction is the wear-resistant, high-capacity option, but it is not maintenance-free — it needs regular greasing to keep friction down and to keep water and grit out. If you want a bearing you never touch again, you want a PTFE-lined type, not this.

Load rating basis — read this rather than a single number:
Torrington rates the SF series differently from a rolling bearing, and the method matters more than any headline figure:

The published dynamic load rating is based on a maximum sliding contact stress of 85 MPa (approximately 12,300 psi), calculated on the radially projected area of the inner ring bore. It is the maximum load recommended for intermittent operation with periodic relubrication.For constant loading and continuous operation, do not exceed 75% of the dynamic rating.For thrust loading, dynamic or static, use 25% of the corresponding radial rating. This is a radial bearing; it will take some axial load but only a quarter of what it takes radially.Combined radial and thrust cases should be referred to the manufacturer’s engineering group.We have not been able to obtain the specific numeric dynamic and static radial rating for the 32SF52 from a manufacturer source, so we are not publishing one. Sizing this bearing off a figure copied from a different bore size would be worse than useless. If you need the rating for a calculation, ask us and we will chase it down against the Timken spherical plain bearing catalogue.

Fitting notes

The outer ring is fractured in one place and held by a snap ring, so it must be supported by the housing bore — the housing is part of the structure, not just a hole. Use the recommended interference fit: the specified fitting practice is what keeps a satisfactory minimum internal clearance in the mounted condition once you account for the coating thickness, outer ring compression and inner ring expansion. Do not remove the snap ring before the bearing is in the housing. Line up your grease path with the lubrication holes in whichever ring you intend to feed through, and grease it on a schedule; a dry steel-on-steel spherical will pick up and score quickly under load.

Brand and obsolescence trail

Torrington spherical plain bearings are now Timken product — The Torrington Company and Fafnir were both consolidated into The Timken Company, and Timken still lists 32SF52 as a Type SF spherical plain bearing. Buyers also search this part under the RBC/Heim B52-L designation and the SKF-style GE82, GE82ZO, GEZ304DO and GEZ304ES designations, all of which describe the same 3-1/4 in bore envelope. Match the seal configuration when you cross: the -2RS and SS variants of those numbers are the sealed bearings, not this unsealed one.