Adjustable Flange Units

What is an adjustable flange unit?

An adjustable flange unit is a two-bolt flange bearing unit with slotted mounting holes, which lets the position of the bearing be fine-tuned after it has been bolted to the machine. Instead of being fixed in one spot, the housing can be moved along the slot to adjust the shaft, so belts, chains, and shafts can be lined up and tensioned during installation and servicing. They are most commonly used on conveyor machinery.

A standard adjustable flange unit is made up of:

• A cast iron adjustable flange housing with two mounting holes, at least one of which is slotted
• A pilot (spigot) on the back of the housing
• A fully sealed, self-aligning insert bearing, seated in a spherical bore in the housing
• Two grub screws that lock the insert to the shaft, and a grease nipple for relubrication.

The slotted mounting holes are what make the unit adjustable.

• With the bolts loosened, the housing can be moved along the slot, shifting the shaft slightly in that direction.
• On some designs, one hole is slotted and the other acts as a pivot, so the housing swings slightly around the fixed bolt to change the shaft position.

Adjustable flange units are sold as complete units with the insert fitted, or as housings on their own, and the insert can be removed and replaced when needed.

Why are adjustable flange units essential?

On many machines, the shaft position needs a small amount of fine-tuning after assembly, to tension a belt or chain, line up two shafts, or make a conveyor belt run true. A standard flange unit is fixed once it is bolted down, so any adjustment means re-drilling or shimming. An adjustable flange unit has that adjustment built in.

This makes installation quicker and servicing easier. As belts stretch and chains wear, the housing can simply be loosened, moved along its slot, and tightened again. The self-aligning insert bearing copes with the small angle changes that come with each adjustment.

Typical applications include:

• Conveyor machinery and roller conveyors
• Belt and chain drives
• Packaging and bottling lines
• Agricultural machinery
• Food processing equipment
• Printing and textile machines
• Fans and blowers
• General machinery where shaft position needs fine adjustment

The main types of adjustable flange units

• Cast iron adjustable flange units - The standard design, with a cast iron two-bolt flange, slotted mounting holes, and a grub screw locking insert. They suit normal duty applications.
• Adjustable flange units with a pilot - Many units have a pilot (spigot) on the back of the flange. This locates the housing in a matching hole or recess, so the unit sits accurately on the shaft line.
• Metric and inch bore units - Adjustable flange units are available for both metric and inch shafts, often in the same housing size for each series.
• Corrosion-resistant units - Stainless steel and thermoplastic versions may be available for wet, washdown, and food applications.

How to choose the right adjustable flange unit?

• Shaft size - Match the insert bearing bore to the shaft, and check whether the shaft is metric or inch.
• Bolt centres and bolt size - Check the distance between the mounting holes and the bolt size suit the frame. For example, a UCFA205 has 98mm bolt centres and takes M10 bolts.
• Amount of adjustment - Check the slot gives enough movement for the belt or chain tension or alignment you need. For larger amounts of travel, a take-up unit may be a better choice.
• Pilot - If the unit has a pilot, check the mounting surface has a hole or recess to suit it, or that there is clearance behind the flange.
• Load and duty - Adjustable flange units suit normal duty applications. For heavy loads, consider a square four-bolt flange or pillow block instead.

Essential references and specialised ranges

How the numbering works:

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

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

FA = adjustable flange housing

The digits = the series and bore code. Multiply the last two digits by five to get the bore in mm, from 04 upwards. Smaller sizes use 01 = 12mm, 02 = 15mm, and 03 = 17mm.

Examples:

UCFA201 = adjustable flange unit for a 12mm shaft

UCFA205 = adjustable flange unit for a 25mm shaft

FA205 = the adjustable flange housing on its own, which takes a UC205 insert

Inch bore units add a suffix showing the bore in sixteenths of an inch:

UCFA202-9 = 9/16 inch shaft

UCFA206-20 = 1-1/4 inch shaft

UCFA208-25 = 1-9/16 inch shaft

UCFA211-32 = 2 inch shaft

UCFA213-40 = 2-1/2 inch shaft

Suffixes:

-9, -20, -25, -32, -40 and similar = inch bore in sixteenths of an inch

E = eccentric collar locking insert

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

FAQ - All you need to know about adjustable flange units

What makes an adjustable flange unit adjustable?

The mounting holes are slotted, so the housing can be moved along the slot before the bolts are tightened. This lets you fine-tune the position of the shaft without re-drilling the frame.

What is the difference between an adjustable flange unit and a take-up unit?

Both let you move a shaft to tension a belt or chain. An adjustable flange unit gives a small amount of fine adjustment along its slotted holes. A take-up unit slides along a frame and is moved with an adjusting screw, giving much more travel.

What is the pilot on the back of the flange for?

The pilot, or spigot, is a raised ring on the back of the housing. It can locate the unit in a matching hole or recess, so the bearing sits accurately on the shaft line.

Do adjustable flange units need lubrication?

Yes. They are supplied greased and have a grease nipple for relubrication. Regrease regularly, especially in dusty, wet, or hot conditions, adding grease slowly until fresh grease just appears at the seals.

How do I adjust an adjustable flange unit?

Loosen the mounting bolts just enough to let the housing move. Slide or pivot the housing along its slot until the belt, chain, or shaft is in the right position, then tighten the bolts evenly. Check the shaft turns freely and the alignment is correct before running the machine.

How do I identify an adjustable flange unit I need to replace?

The reference is usually cast on the housing and marked on the insert bearing. If it cannot be read, measure the shaft diameter, the bolt hole centres, the bolt hole size, the overall length and height of the housing, and the pilot diameter if there is one.

What are the signs that an adjustable flange unit needs replacing?

Look out for:

• Grinding, squealing, or rumbling from the bearing
• More vibration than normal
• The housing running hot
• Play in the shaft
• Grease leaking past the seals
• The housing slipping along its slots, or loose mounting bolts
• A cracked housing or worn slots