Solid Bronze Bushings

What are solid bronze bushings?

Solid bronze bushings are plain bearings machined from solid cast bronze. They give a tough, wear-resistant bearing surface for shafts and pins that rotate, oscillate, or slide. Unlike self-lubricating bushes, solid bronze bushings are lubricated with grease or oil, often through a lubrication hole and groove in the bush. Their strength and resistance to shock make them a long-established choice for heavy-duty agricultural and industrial machinery.

A standard solid bronze bushing is made up of:

• A solid body of cast bronze, which carries heavy and shock loads
• A precision-machined bore and outside diameter
• Often a lubrication hole and groove, which carry grease or oil to the bearing surface
• A plain cylindrical shape, or a cylinder with a flange at one end.

Solid bronze is tough and forgiving.

• Bronze is softer than a steel shaft, so the bush wears in preference to the shaft, protecting the more expensive part.
• It copes well with dirt, shock loads, vibration, and a less-than-perfect shaft finish, which makes it reliable in harsh conditions.

Solid bronze bushings are made to standard dimensions, such as ISO 4379 and DIN 1850, and are sized by their bore, outside diameter, and length.

Why are solid bronze bushings essential?

Solid bronze bushings are a simple, robust bearing for pivots, linkages, and shafts that carry heavy loads at low speeds, or that move back and forth rather than turning continuously. They handle impact loads and vibration well, keep working in dirty environments, and resist corrosion, so they are widely used on farm, construction, and industrial machinery.

Because they are solid metal, they can be pressed into housings for a firm fit and, unlike porous self-lubricating bushes, can be machined or reamed to size if needed. With regular lubrication, they give long and dependable service.

Typical applications include:

• Agricultural machinery pivots and linkages
• Construction and earthmoving equipment
• Hydraulic cylinder eyes and clevis pins
• Cranes, hoists, and lifting equipment
• Pumps, gearboxes, and industrial machinery
• Conveyor and handling equipment
• Marine equipment
• Machine tools and presses

The main types of solid bronze bushings

• Plain solid bronze bushes - Straight, cylindrical bushes that are pressed into a housing to support a shaft or pin radially.
• Flanged solid bronze bushes - Bushes with a flange at one end, which locates the bush in the housing and takes axial loads in one direction against a shoulder or collar.
• Bushes with lubrication holes and grooves - Bushes with a hole and a groove machined in the bore, which spread grease or oil along the bearing surface from a grease nipple or oil supply.
• Metric solid bronze bushes - Made in standard metric sizes, with bore, outside diameter, and length in millimetres.
• Solid bronze bar and tube - Bronze stock for machining custom bushes where a standard size is not available.

How to choose the right solid bronze bushings?

• Size - Choose a bush with a bore to suit the shaft, an outside diameter to suit the housing, and a length to suit the space available.
• Plain or flanged - Choose a flanged bush where the bush needs locating in the housing or where there is an axial load. Choose a plain bush where there is only a radial load.
• Lubrication - Choose a bush with a lubrication hole and groove if it will be greased or oiled in service. Make sure the housing has a grease nipple or oil supply that lines up with the hole.
• Movement and load - Solid bronze bushes suit heavy loads at low speeds, and oscillating, rotating, or sliding movement. For very high speeds, a different bearing type may be better.
• Maintenance - Solid bronze bushes need regular lubrication. Where lubrication is difficult, consider an oilless or oil filled bush instead.

Essential references and specialised ranges

How the numbering works:

Solid bronze bushings are usually referenced by a type code followed by the bore, outside diameter, and length, in millimetres:

PBM = plain solid bronze bush

PBMF = flanged solid bronze bush

Examples:

PBM142020 = plain bush, 14mm bore, 20mm outside diameter, 20mm long

PBM202830 = plain bush, 20mm bore, 28mm outside diameter, 30mm long

PBMF121810 = flanged bush, 12mm bore, 18mm outside diameter, 10mm long

The flange diameter and thickness are given in the product details for each flanged bush.

Suffixes:

In the widely used SKF system, suffixes after the dimensions describe the material and features:

M1 = the bronze material used for the bush

G1 = a lubrication hole and groove in the bore

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

FAQ - All you need to know about solid bronze bushings

Do solid bronze bushings need lubrication?

Yes. Unlike self-lubricating bushes, solid bronze bushes need grease or oil. Lubricate them when fitting, and regularly in service through the grease nipple or lubrication hole.

What is the difference between solid bronze and oilless bronze bushes?

Solid bronze bushes are plain bronze and need grease or oil. Oilless bronze bushes have solid graphite inserts in the bearing surface, so they lubricate themselves and need no maintenance.

What is the difference between solid bronze and oil filled bushes?

Oil filled bushes are made from porous sintered bronze soaked in oil, and lubricate themselves at lighter loads. Solid bronze bushes are made from dense cast bronze, carry heavier and shock loads, and need regular lubrication.

Can solid bronze bushes be reamed or machined?

Yes. Because they are solid, not porous, solid bronze bushes can be reamed or machined to size after fitting if needed, which is useful when replacing worn bushes on older machinery.

How do I fit a solid bronze bush?

Press the bush squarely into the housing using a press and a fitting mandrel, never by hammering directly on it. Line up the lubrication hole with the grease nipple or oil supply. Check the shaft runs freely, and grease or oil the bush before running.

How do I identify the bush I need?

Check the reference on the old bush or in the machine’s parts list. If it cannot be read, measure the bore, outside diameter, and length with callipers, and on a flanged bush, the flange diameter and thickness. Note whether the old bush had a lubrication hole or groove.

How can I tell if a solid bronze bush needs replacing?

Warning signs include:

• Squeaking, knocking, or grinding from the pivot or shaft
• Play or wobble in the shaft or pin
• An oval-shaped or heavily worn bore
• Scoring or scuffing caused by a lack of lubrication
• Grease no longer reaching the bearing surface
• The bush moving or turning in its housing