Plastic Bushings

What are plastic bushings?

Plastic bushings, also called polymer bushes or plastic plain bearings, are plain bearings made from engineered plastics instead of metal. They are light, corrosion-free, and quiet, and many grades contain solid lubricants mixed into the plastic, so they run without oil or grease. This makes them a popular choice for food processing, marine equipment, and any application where lubrication is unwanted, impractical, or would attract dirt.

A standard plastic bushing is made up of:

• A body made from an engineered polymer, often blended with reinforcing fibres for strength
• Solid lubricants built into the material, which keep friction low
• A precision-moulded bore and outside diameter
• A plain cylindrical shape, or a cylinder with a flange at one end.

The self-lubricating material is what makes plastic bushes maintenance-free.

• The solid lubricants are spread throughout the material, so as the surface wears, fresh lubricant is always exposed.
• Because no oil or grease is needed, dust and dirt do not stick to the bearing, and there is nothing to contaminate food or other products.

Plastic bushings are sized by their bore, outside diameter, and length, with flange diameter and thickness on flanged bushes.

Why are plastic bushings essential?

Plastic bushings give a light, low-cost, maintenance-free bearing that will not rust or corrode. They work well in wet, washdown, and outdoor conditions where metal bearings would corrode, and in food and packaging machinery where oil and grease are not allowed. They also run quietly, absorb vibration, and handle dirt and dust better than lubricated bearings.

Different polymer grades are available to suit different loads, speeds, temperatures, and chemicals, so there is a plastic bush for everything from light hinges to medium-load machinery.

Typical applications include:

• Food processing and packaging machinery
• Marine and boat equipment
• Agricultural and garden machinery
• Medical, laboratory, and cleanroom equipment
• Automotive components, such as pedals and seat mechanisms
• Furniture, fitness equipment, and consumer products
• Linear guides and automation equipment
• Pivots, hinges, and linkages

The main types of plastic bushings

• Plain plastic bushes - Straight, cylindrical bushes that are pressed into a housing to support a shaft radially.
• Flanged plastic bushes - Bushes with a flange at one end, which locates the bush in the housing and takes light axial loads against a shoulder or collar.
• General-purpose grades - All-round polymer bushes for medium loads, medium speeds, and medium temperatures, typically up to around +130°C. A cost-effective choice for most applications.
• High-temperature grades - Polymer bushes made from heat-resistant plastics, for applications running hotter than general-purpose grades can handle.
• Food-grade and chemical-resistant grades - Bushes made from materials suitable for contact with food, or for resistance to aggressive cleaning chemicals.
• Plastic thrust washers - Flat washers made from the same materials, for axial loads alongside a bush.

How to choose the right plastic 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 a light axial load. Choose a plain bush where there is only a radial load.
• Load and speed - Plastic bushes suit low to medium loads and moderate speeds. For heavy or shock loads, a bronze or steel-backed bush may be better.
• Temperature - Check the polymer grade suits the operating temperature. General-purpose grades typically work from around -40°C up to around +130°C.
• Environment - Choose plastic bushes for wet, washdown, corrosive, or food applications, and check the grade is compatible with any chemicals present.
• Shaft - Plastic bushes work with a wide range of shaft materials, but a smooth shaft gives the longest life.

Essential references and specialised ranges

How the numbering works:

Plastic bushes are usually referenced by a code for the material and type, followed by the bore, outside diameter, and length, in millimetres. In one widely used range:

The first letter = the polymer grade

S = sleeve (plain) bush

F = flanged bush

M = metric sizes

Examples:

GSM-0810-10 = plain metric bush in G grade, 8mm bore, 10mm outside diameter, 10mm long

GFM-0506-05 = flanged metric bush in G grade, 5mm bore, 6mm outside diameter, 5mm long

The flange diameter and thickness are given in the product details for each flanged bush. For example, the GFM-0506-05 has a 10mm flange diameter and 0.5mm flange thickness.

Suffixes:

S = sleeve (plain) bush

F = flanged bush

M = metric

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

FAQ - All you need to know about plastic bushings

Do plastic bushings need lubrication?

No. Most plastic bushes contain solid lubricants and are designed to run dry. Adding grease is not needed and can attract dirt, although a small amount at fitting will not harm most grades.

What is the difference between plastic and bronze bushes?

Plastic bushes are lighter, corrosion-free, quieter, and maintenance-free, and suit low to medium loads. Bronze bushes carry heavier and shock loads and handle higher temperatures, but are heavier and may need lubrication.

Can plastic bushes be used in water?

Yes. Plastic bushes do not rust or corrode, so they are well suited to wet, washdown, and marine applications. Check the grade, as some plastics absorb a little water and swell slightly.

Are plastic bushes suitable for food machinery?

Yes, plastic bushes are widely used in food machinery as they need no oil or grease. For direct food contact, choose a grade that is approved for food use.

How do I fit a plastic bush?

Press the bush squarely into a clean, correctly sized housing using a press or a fitting mandrel, never by hammering directly on it. The bore closes slightly when the bush is pressed in, so check the shaft runs freely afterwards. Do not ream or machine the bore.

How do I identify the bush I need?

Check the reference on the bush packaging 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.

How can I tell if a plastic bush needs replacing?

Warning signs include:

• Play or wobble in the shaft
• Squeaking or increased friction
• Visible wear, grooves, or an oval-shaped bore
• Cracks, melting, or deformation from heat or overload
• The bush moving or turning in its housing
• Swelling or softening from chemicals or moisture