Square Housings

What is a square housing?

A square housing is a four-bolt flange bearing housing, designed to mount a shaft where it passes through a wall, panel, or machine frame. The square flange has a bolt hole in each corner, so the bearing is clamped firmly to the mounting surface on all four sides. This makes it one of the most rigid and secure ways to support a shaft that runs at right angles to a frame.

A standard square housing unit is made up of:

• A square cast iron flange with four bolt holes, one in each corner
• A self-aligning insert bearing, held in a spherical seat in the centre of the flange
• A locking device that secures the insert bearing to the shaft
• A grease nipple for relubrication, and seals on both sides of the insert bearing.

The four-bolt fixing is what sets a square housing apart.

• Clamping at four points holds the housing square to the mounting face and resists twisting, tilting, and vibration.
• The load from the shaft is spread evenly into the frame, which reduces stress on the bolts and the mounting surface.

Square housings are sold as complete units with the insert bearing already fitted, or as housings on their own so the insert can be replaced separately.

Why are square housings essential?

Where a shaft has to pass through the side of a machine, a square housing gives a strong, ready-made bearing support that simply bolts on. There is no need to machine a bore in the frame or design a separate housing. Because the flange is clamped at four corners, it stays firmly in place on machines that vibrate, start and stop frequently, or carry shock loads, such as fans, crushers, and conveyor drive ends.

The self-aligning insert bearing takes care of small alignment errors between the two sides of a machine, which makes fitting much quicker. With standard sizes in metric and inch bores, square housings are easy to source and swap, keeping downtime short when a bearing needs changing.

Typical applications include:

• Fan and blower shafts passing through casings
• Conveyor drive and return pulleys
• Agricultural machinery, such as balers and harvesters
• Mixers and agitators
• Crushers and screening equipment
• Vibrating machinery
• Pumps and compressors
• Woodworking and sawmill machinery
• Food processing and packaging lines

The main types of square housings

• Cast iron square flange units - The standard choice for most industrial machinery. Cast iron is strong, absorbs vibration well, and can be used across a wide range of loads and speeds.
• Heavy-duty square flange units - These use a larger, heavier insert bearing from the 300 series, giving higher load ratings for the same shaft size. They suit heavily loaded or shock-loaded machinery.
• Square flange units with a spigot - These have a raised spigot on the back of the flange, which fits into a machined hole in the mounting surface. The spigot centres the housing accurately and takes some of the load off the bolts.
• Pressed steel square flanges - Two pressed steel plates clamped around the insert bearing. They are light and low in cost, and best suited to light-duty equipment.
• Thermoplastic and stainless steel square flanges - These resist corrosion and are suited to food processing, washdown, and wet environments. Thermoplastic types are not suited to high temperatures or heavy loads.
• Square flange units with end covers - An open cover allows the shaft to pass through, while a closed cover seals the end of the shaft. Both add protection from dirt and water, and closed covers also act as a guard at the shaft end.

Locking options include:

• Grub screws - The simplest method, suited to most applications and to drives that run in both directions.
• Eccentric collars - Grip the shaft without marking it, and are best suited to drives that run in one direction.
• Adapter sleeves - Use a tapered sleeve and nut to clamp the bearing to the shaft, giving the best concentricity for higher speeds, heavy loads, and reversing drives.

How to choose the right square housing?

• Shaft diameter - Match the insert bearing bore to the shaft. Metric and inch shafts are not interchangeable, so check which you have.
• Load and duty - For general use, a standard cast iron unit is the right choice. For heavy, shock, or vibrating loads, choose a heavy-duty 300 series unit or an adapter sleeve locking insert.
• Mounting surface - The frame must be flat, rigid, and square to the shaft, with room for all four bolts and their washers. A spigot version needs a machined hole in the frame to locate it.
• Through shaft or shaft end - If the shaft passes right through, use an open end cover or no cover. If the shaft ends inside the housing, a closed end cover will seal and guard it.
• Environment - In wet, corrosive, or washdown conditions, choose stainless steel or thermoplastic housings and stainless insert bearings.
• Locating and non-locating - On a shaft with a housing at each end, lock one bearing firmly to locate the shaft. Thermal expansion is then taken up at the other end.

Essential references and specialised ranges

How the numbering works:

Square flange unit references are made up of three parts:

UC = the insert bearing, with grub screw locking and an extended inner ring

F = a square four-bolt flange housing

The digits = the series and bore. 2 is the standard series and 3 is the heavier series. The last two digits are the bore code, multiplied by five to give the bore in mm.

Examples:

UCF205 = standard square flange unit for a 25mm shaft

UCF210 = standard square flange unit for a 50mm shaft

UCF308 = heavy-duty square flange unit for a 40mm shaft

F205 = the square flange housing on its own, which takes a UC205 insert

Inch bore units add a suffix showing the bore in sixteenths of an inch, so a UCF207-20 fits a 1-1/4 inch shaft.

Suffixes:

E = eccentric collar locking insert

-16, -20, -24 and similar = inch bore in sixteenths of an inch (for example, -16 = 1 inch, -24 = 1-1/2 inch)

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

FAQ - All you need to know about square housings

When should I use a square housing instead of an oval housing?

Choose a square housing when the load is heavier, when the machine vibrates or carries shocks, or when you need the housing to stay rigidly in place. Choose an oval two-bolt housing when space on the mounting surface is limited and loads are light.

Can a square housing be mounted with the shaft vertical?

Yes. The housing can be bolted to any flat surface, so the shaft can be horizontal, vertical, or at an angle. With a vertical shaft, make sure the axial load from the weight of the shaft and parts is within the bearing’s capacity.

What does the spigot on some square housings do?

The spigot is a raised ring on the back of the flange that fits into a machined hole in the frame. It centres the housing accurately on the shaft line and helps carry the load, so the bolts are not doing all the work.

How often should a square housing be regreased?

It depends on the speed, load, temperature, and how dirty the conditions are. Lightly loaded units in clean conditions may need little or no regreasing, while units in dusty, wet, or hot conditions need regular top-ups. Add grease slowly while the shaft is turning, if it is safe to do so, and stop as soon as fresh grease appears at the seals.

What is the best way to fit a square housing?

Slide the unit onto the clean, burr-free shaft and fit all four bolts loosely. Line up the shaft, then tighten the bolts evenly in a diagonal pattern so the flange sits flat against the frame. Lock the insert bearing to the shaft last, once everything is aligned and bolted down.

How do I identify a square housing I need to replace?

Look for the reference cast into the flange and stamped on the insert bearing. If you cannot read it, measure the shaft diameter, the flange size across the square, the distance between the bolt hole centres, and the bolt hole diameter. Also check whether it has a spigot and what type of locking it uses.

What are the signs that a square housing needs replacing?

Look out for:

• Noise from the bearing, such as grinding, squealing, or knocking
• More vibration than usual
• The housing running hot to the touch
• Movement or play in the shaft
• Grease escaping past the seals
• Cracks in the flange, or loose mounting bolts
• The insert bearing turning in the housing, or the shaft slipping in the bearing