Round Housings

What is a round housing?

A round housing, also called a round flange or flanged cartridge housing, is a bearing housing with a circular flange and bolt holes spaced evenly around it. It is designed to mount a shaft at the end of a machine or through a round opening, with the shaft at right angles to the mounting face. Most round housings have a spigot on the back, which locates the housing in a matching hole, so the bearing is held exactly on the line of the shaft.

A typical round housing unit includes:

• A circular flange, usually cast iron, with four bolt holes on a pitch circle
• A spigot on the back of the flange, which fits into a bored hole in the mounting surface
• A self-aligning insert bearing, seated in a spherical bore in the centre
• A locking device to secure the insert to the shaft, plus seals and a grease nipple.

The spigot and round flange work together.

• The spigot centres the housing precisely, so the shaft runs true without the need for careful alignment of the bolts.
• The round shape lets the housing be fitted into a bored opening or recess, and turned to any angle to place the grease nipple where it is easiest to reach.

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

Why are round housings essential?

Round housings are the natural choice where a shaft needs to be supported at the end of a machine, in a gearbox or motor end plate, or through a round hole in a frame. The spigot does the centring, so the housing goes straight onto the shaft line, which saves time and gives an accurate, repeatable fit when a bearing is changed.

Bolting around a full circle spreads the load evenly, and the compact circular shape fits neatly into round end caps, drums, and tube ends where a square or oval flange would not fit. As with other insert bearing housings, the self-aligning seat copes with small errors between bearings at each end of the shaft.

Typical applications include:

• Ends of conveyor pulleys and drums
• Motor, fan, and pump end plates
• Gearbox and drive shaft supports
• Agricultural machinery, such as augers and spreaders
• Screw conveyors and feeders
• Mixers and agitators
• Rollers in printing and textile machines
• Food processing and packaging machinery

The main types of round housings

• Cast iron round flange units with spigot - The most common design. The spigot locates the unit in a bored hole and the four bolts clamp it in place, giving a secure and accurately centred fit.
• Round flange units without spigot - These bolt directly to a flat face and are centred by the bolt holes. They suit simpler mounting surfaces where a bored locating hole is not available.
• Heavy-duty round flange units - These take a larger 300 series insert bearing, giving higher load capacity for the same shaft size.
• Pressed steel round flanges - Light, low-cost flanges made from pressed steel plates, often with three bolt holes. They suit light-duty equipment such as agricultural and garden machinery.
• Thermoplastic and stainless steel round flanges - Corrosion-resistant versions for food processing, washdown, and outdoor equipment. Thermoplastic types suit lighter loads and lower temperatures.
• Round flange units with end covers - Open covers for shafts that pass through, and closed covers to seal and guard the end of a shaft.

Locking options include:

• Grub screws - Easy to fit, suitable for most applications and for drives that run both ways.
• Eccentric collars - Clamp the shaft without marking it, and best used on drives that turn in one direction.
• Adapter sleeves - Clamp the bearing with a tapered sleeve and nut, for heavier loads, higher speeds, and reversing drives.

How to choose the right round housing?

• Shaft diameter - The insert bearing bore must match the shaft. Make sure you know whether the shaft is metric or inch.
• Spigot or no spigot - Choose a spigot type if the mounting surface can be bored to take it, for the most accurate centring. Choose a type without a spigot for a plain flat mounting face.
• Spigot and bolt circle sizes - Check the spigot diameter, the pitch circle diameter of the bolt holes, and the flange diameter suit the mounting surface or the housing being replaced.
• Load - Standard cast iron units suit most general machinery. For heavier or shock loads, choose a 300 series unit. For light duty, pressed steel or thermoplastic flanges may be enough.
• Shaft end or through shaft - Fit a closed end cover where the shaft finishes inside the housing, or an open cover where it passes through.
• Conditions - Use stainless steel or thermoplastic for wet, corrosive, and washdown environments.

Essential references and specialised ranges

How the numbering works:

Round flange unit references combine the insert bearing and the housing:

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

FC = round flange housing, usually with a spigot

The digits = the series and bore code. 2 is the standard series and 3 is the heavier series. Multiply the last two digits by five to get the bore in mm.

Examples:

UCFC204 = round flange unit for a 20mm shaft

UCFC206 = round flange unit for a 30mm shaft

UCFC208 = round flange unit for a 40mm shaft

FC206 = the round flange housing on its own, which takes a UC206 insert

Inch bore units add a suffix showing the bore in sixteenths of an inch, so a UCFC206-18 fits a 1-1/8 inch shaft.

Suffixes:

E = eccentric collar locking insert

-16, -18, -20 and similar = inch bore in sixteenths of an inch (for example, -18 = 1-1/8 inch)

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

FAQ - All you need to know about round housings

Where are round housings used instead of square or oval housings?

Round housings are best where the bearing fits into a round opening or end plate, or where accurate centring is important. Square housings suit heavier loads on flat frames, and oval housings suit narrow spaces.

Do I need to bore a hole for the spigot?

If you are using a spigot type, yes. The mounting surface needs a bored hole that matches the spigot diameter, so the housing sits on the shaft line. If boring is not possible, choose a round flange without a spigot.

Can I turn the housing to move the grease nipple?

Yes. Because the flange is round and the bolts are evenly spaced, the housing can usually be fitted in several positions. Choose the position that puts the grease nipple where it is easiest to reach.

How do I lubricate a round housing?

Most units are supplied greased and have a grease nipple for topping up. In dusty, wet, or hot conditions, regrease regularly. Pump grease in slowly and stop when fresh grease starts to appear at the seals, as over-greasing can push the seals out.

How do I fit a round housing?

Clean the shaft and remove any burrs, then slide the unit on. Push the spigot fully into its hole, fit the bolts, and tighten them evenly around the flange. Only lock the insert to the shaft once the housing is bolted down and the shaft turns freely.

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

The reference is normally cast on the flange and marked on the insert bearing. If it cannot be read, measure the shaft diameter, the flange diameter, the spigot diameter, the pitch circle diameter of the bolt holes, and the bolt hole size. Note how many bolt holes there are and what type of locking it uses.

What are the signs that a round housing is failing?

Watch for:

• Grinding, rumbling, or squealing from the bearing
• More vibration than normal
• The housing getting hot
• Play or wobble in the shaft
• Grease leaking past the seals
• A cracked flange or loose bolts
• The insert turning in the housing, or the shaft slipping in the insert