Oval Housings

What is an oval housing?

An oval housing, also called an oval flange or two-bolt flange housing, is a compact bearing housing with an oval-shaped flange and two bolt holes. It bolts flat against a vertical surface, such as a machine side plate or frame, with the shaft passing through at right angles to that surface. Like a pillow block, it holds an insert bearing ready to fit, but its slim two-bolt shape makes it ideal where space is tight.

A standard oval housing unit has four main parts:

• An oval flange housing with two bolt holes, usually made of cast iron
• An insert bearing, which is a deep groove ball bearing with a spherical outer ring and an extended inner ring
• A locking method, such as grub screws or an eccentric collar, which fixes the bearing to the shaft
• Seals on the insert bearing, and usually a grease nipple on the housing.

The spherical seat in the housing lets the insert bearing self-align.

• The spherical outer ring of the insert sits in a matching spherical bore in the housing.
• This allows the bearing to adjust to small mounting errors and shaft deflection when it is fitted.

Oval housings can be bought as complete units, with the insert bearing fitted, or as a housing on its own.

Why are oval housings essential?

They give a quick, compact way to support a shaft where it passes through a wall or side plate. With only two bolts and a narrow flange, an oval housing takes up less space than a square four-bolt flange, so it fits on narrow frames and close to other parts. The self-aligning seat means the housings on each side of a machine do not need to be perfectly lined up.

They are easy to fit and replace, and come in standard sizes, so they are easy to source. They suit light to medium loads, and are widely used on conveyors, agricultural equipment, and general machinery.

Typical applications include:

• Conveyors and roller beds
• Agricultural machinery
• Fans and blowers
• Packaging machines
• Food and beverage processing
• Woodworking machinery
• Printing machines
• Textile machinery
• Gates, doors, and light-duty mechanisms

The main types of oval housings

• Cast iron oval housings - These are the standard design and by far the most common. They are strong, rigid, and suited to most industrial applications.
• Pressed steel oval housings - These are made from two pressed steel flanges clamped around the insert bearing. They are light and low in cost, and suit lighter loads and speeds.
• Thermoplastic oval housings - These have a housing made of glass-filled nylon or a similar polymer. They are light, corrosion resistant, and non-metallic, but not suited to high temperatures or heavy loads.
• Stainless steel oval housings - These have a stainless steel housing and insert bearing, for washdown, food, and corrosive environments.
• Oval housings with end covers - These have an open or closed cover fitted over the end of the housing, for extra protection from dirt and water, or for safety at the end of a shaft.

Locking methods include:

• Grub screw locking - Two grub screws in the inner ring press onto the shaft. Simple and works in both directions of rotation.
• Eccentric collar locking - A collar is turned onto the inner ring and locked with a grub screw. It grips the shaft without marking it, but is best suited to drives that run in one direction.

How to choose the right oval housing?

• Shaft size - The bore of the insert bearing must match the shaft diameter. Check whether the shaft is metric or inch, as they are not interchangeable.
• Mounting - Check the bolt hole spacing, bolt size, and overall flange length suit the mounting surface. The mounting face must be flat and square to the shaft.
• Load and speed - Oval housings suit light to medium loads. For heavier loads, a square four-bolt flange or pillow block may be a better choice. Choose cast iron for general use, and pressed steel or thermoplastic for lighter duty.
• Locking method - Use grub screws for general use and reversing drives, or an eccentric collar where the shaft must not be marked and the drive runs in one direction.
• Environment - Use stainless steel or thermoplastic housings for wet, washdown, or corrosive conditions. Add end covers in very dirty conditions or at exposed shaft ends.

Essential references and specialised ranges

How the numbering works:

Oval housing unit numbers combine the insert bearing and housing:

The first two letters, UC. Identify the insert bearing type, a grub screw locking insert with an extended inner ring.

The next letters identify the housing: FL = oval two-bolt flange (for example, UCFL).

The digits give the series and bore. The 2 series is the standard series. The last two digits are the bore code, so 05 × 5 = 25mm.

For example, UCFL205 is a cast iron oval flange unit with a UC205 insert for a 25mm shaft. The housing on its own is an FL205.

Inch bore versions add a suffix showing the bore in sixteenths of an inch, so a UCFL205-16 fits a 1 inch shaft.

Other manufacturers use their own codes for oval flange units, so always check the shaft diameter and bolt spacing before ordering.

Suffixes:

E = eccentric collar locking insert (for example, UC205E)

-16, -20, and similar = inch bore in sixteenths of an inch (for example, -16 = 1 inch)

Suffix codes vary between manufacturers, so check the supplier’s catalogue for the exact meaning.

FAQ - All you need to know about oval housings

What is the difference between an oval housing and a square flange housing?

An oval housing has two bolt holes and a narrow, oval flange, so it takes up less space. A square flange housing has four bolt holes and carries heavier loads, but needs more room on the mounting surface.

What is the difference between an oval housing and a pillow block?

A pillow block bolts to a flat surface with the shaft running parallel to it, such as on top of a frame. An oval housing bolts to a vertical surface with the shaft passing through it at right angles, such as through a side plate.

Can I buy the housing and insert bearing separately?

Yes. Housings and insert bearings are sold separately as well as together as units. Make sure the insert bearing matches the housing size, so the spherical outer ring fits the housing seat correctly.

Do oval housings need lubrication?

Most oval housing units are supplied pre-greased, and many have a grease nipple so the bearing can be relubricated. Relubricate slowly with the correct grease, as too much can damage the seals.

Can I replace an oval housing myself?

In most cases, yes. Loosen the locking screws or collar, undo the two mounting bolts, and slide the old unit off the shaft. Clean the shaft and remove any burrs, then slide the new unit on, bolt it to the mounting surface, and lock it to the shaft last, once the housings are aligned. Never hammer on the housing or bearing.

How do I identify an oval housing I need to replace?

The reference is usually cast into the housing and marked on the insert bearing. If the markings are worn away, measure the shaft diameter, the distance between the bolt hole centres, the bolt hole size, and the overall flange length. Also note the locking method and housing material.

How can I tell if an oval housing is worn or failing?

Warning signs include:

• Grinding, rumbling, or squealing noises
• Increased vibration
• The bearing running hot
• Play in the shaft
• Grease leaking from the seals
• A cracked or damaged flange
• The insert bearing turning in the housing, or the shaft turning in the bearing