Triangular Housings

What is a triangular housing?

A triangular housing is a compact, three-bolt flange bearing housing, usually made from pressed steel. Two pressed steel flange plates are clamped together around a self-aligning insert bearing, and the triangular flange is bolted to a flat surface with three bolts. The result is a light, low-cost shaft support that fits neatly into tight spaces and corners.

A standard triangular housing unit is made up of:

• Two pressed steel triangular flange plates, each with three bolt holes
• A self-aligning insert bearing, held between the two plates
• A locking method, either an eccentric collar or grub screws, that fixes the insert to the shaft
• Seals on the insert bearing, which is usually greased for life.

The pressed steel construction is what makes triangular housings so light.

• The two flange plates are pressed from sheet steel and shaped to hold the spherical outside of the insert, so the bearing can still self-align when it is bolted down.
• The thin plates take up very little space along the shaft, and weigh far less than a cast iron housing.

Triangular units are sold as complete units, with the insert bearing already clamped between the plates.

Why are triangular housings essential?

They give a simple, economical way to support a shaft in light-duty equipment. Three bolts give a stable fixing that resists rocking, while the small triangular shape fits into corners and narrow frames where a larger flange would not fit. Because they are pressed rather than cast, they are light and low in cost, which makes them a popular choice for machinery built in large numbers.

The self-aligning insert copes with moderate misalignment between the housings on each side of a machine, so installation is quick and forgiving.

Typical applications include:

• Light conveyors and roller conveyors
• Agricultural machinery and implements
• Garden and grounds care equipment
• Film processing and printing equipment
• Packaging machines
• Fans and ventilation equipment
• Fitness and leisure equipment
• General light industrial machinery

The main types of triangular housings

• Triangular units with eccentric collar inserts (SAPFT) - These use an insert that locks to the shaft with an eccentric collar and grub screw. The collar grips the shaft without marking it, and suits drives that run in one direction.
• Triangular units with grub screw inserts (SBPFT) - These use a narrow insert that locks to the shaft with grub screws in the inner ring. They are simple to fit and suit drives that run in either direction.
• Triangular units with full width inserts (UCPFT) - These use a standard full width UC insert with grub screw locking, for a wider bearing and a firmer grip on the shaft.
• Metric and inch bore units - Triangular units are available for metric and inch shafts, typically from 12mm to 35mm and the inch equivalents.

How to choose the right triangular housing?

• Shaft size - Match the insert bearing bore to the shaft, and check whether the shaft is metric or inch.
• Locking method - Choose an eccentric collar insert where the shaft must not be marked and the drive runs in one direction, or a grub screw insert for drives that run both ways.
• Mounting - Check the bolt hole spacing and size suit the frame, and that the mounting surface is flat so the pressed steel plates are not distorted when the bolts are tightened.
• Load and duty - Triangular pressed steel units suit light loads and moderate speeds. For heavier loads or shock, choose a cast iron flange or pillow block instead.
• Conditions - Pressed steel units are usually painted or plated. For wet or corrosive conditions, choose a corrosion-resistant unit or a different housing material.

Essential references and specialised ranges

How the numbering works:

Triangular unit references combine the insert bearing and the housing:

SA = insert bearing with eccentric collar locking

SB = narrow insert bearing with grub screw locking

UC = full width insert bearing with grub screw locking

PFT = pressed steel triangular flange housing

The digits = the series and bore code. 01 = 12mm, 02 = 15mm, and 03 = 17mm. From 04 upwards, multiply by five to get the bore in mm.

Examples:

SAPFT204 = triangular unit with an eccentric collar insert for a 20mm shaft

SBPFT205 = triangular unit with a grub screw insert for a 25mm shaft

UCPFT207 = triangular unit with a full width insert for a 35mm shaft

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

SAPFT201-8 = 1/2 inch shaft

SBPFT204-12 = 3/4 inch shaft

SAPFT205-16 = 1 inch shaft

SAPFT207-23 = 1-7/16 inch shaft

Suffixes:

-8, -12, -16, -23 and similar = inch bore in sixteenths of an inch

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

FAQ - All you need to know about triangular housings

What is the difference between a triangular housing and a bracket housing?

Both have three bolt holes. Triangular housings are usually made from two pressed steel plates, which makes them light and low in cost. Bracket housings are usually cast iron, which makes them heavier but stronger and better suited to higher loads.

What do SA and SB mean in the reference?

They describe the insert bearing. SA inserts lock to the shaft with an eccentric collar, while SB inserts are narrower and lock with grub screws in the inner ring.

Can I replace just the insert bearing?

On most pressed steel units, the insert is clamped between the two plates, so it is usually simplest to replace the complete unit. Check with the supplier if you need to replace only the insert.

Do triangular housings need lubrication?

Most pressed steel triangular units are greased and sealed for life, so they do not need relubricating. In dusty or wet conditions, check them regularly and replace them if the seals are damaged or the bearing becomes rough.

How do I fit a triangular housing?

Slide the unit onto the clean, burr-free shaft and fit the three bolts. Tighten them evenly, without overtightening, so the pressed steel plates are not bent. Once both ends of the shaft are bolted down and it turns freely, lock the collar or grub screws onto the shaft.

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

The reference is usually stamped on the flange or marked on the insert bearing. If it cannot be read, measure the shaft diameter, the bolt hole spacing, the bolt hole size, and the overall size of the flange. Also check whether the insert has an eccentric collar or grub screws.

What are the signs that a triangular housing needs replacing?

Look out for:

• Grinding, squealing, or rattling from the bearing
• Rough or uneven rotation
• Play in the shaft
• The bearing running hot
• Damaged or missing seals
• Bent, cracked, or loose flange plates
• The shaft slipping in the insert bearing