Bearings.

What are Bearings?

Bearings are the rotary components that let one part move against another with as little friction as possible while carrying a load between them. Nearly every machine that turns, rolls or slides depends on them and they fall into two broad families: rolling or plain bearings. Rolling bearings run hardened balls or rollers between an inner and outer race, so the surfaces roll rather than rub. Plain bearings, also known as bushings, do away with rolling elements entirely and instead offer a low-friction sacrificial surface for the parts to slide against.

How Bearings Work

Most bearings work by replacing sliding friction with rolling friction. In a rolling bearing, a ring of balls or cylinders, also known as needles, sits between an inner and outer race, so as the shaft turns the balls or needles roll along the raceways rather than dragging against a fixed surface. This helps to minimise friction, heat and wear. Plain bearings rely instead on a self-lubricating material that is simply slippery enough to slide against, with the design intent that they will eventually need to be replaced. 

The geometry dictates which bearing is right for your application. Radial bearings carry load across the shaft, thrust bearings take load along their axis and linear bearings let a carriage travel in a straight line. Shields and rubber seals close the bearing so grease stays in and contamination stays out, which is why sealed bearings are the default in dusty or wet conditions.

In an industrial setting, bearings support the shafts in electric motors, gearboxes, pumps, conveyors and machine tool spindles, taking the radial and axial loads those machines throw at them for years at a time. They are just as central to hobbyist and prototype work. A 3D printer is a good example, where miniature and deep groove ball bearings guide the belts and idler pulleys, linear bearings run the print head smoothly along its hardened rods and a small thrust bearing can sit beneath a rotating build plate or turntable. Industrial bearings and desktop-scale bearings share exactly the same principles, only the size and load change.

Materials Bearings Are Made From

Accu's bearings are made across a spread of metals and engineering-grade plastics, so the material can be matched to the load, the speed and the working environment.

• Steel - (AISI 52100): A high-carbon chromium alloy steel. It boasts a high uniform hardness with excellent wear resistance and fatigue life.
• Stainless Steel - (440 and 420): Corrosion-resistant martensitic stainless grades. 440 hardens closer to bearing-steel levels for higher loads, while 420 trades a little hardness for wet or chemically exposed work.
• Plastic - POM and Xirodur: Lightweight, self-lubricating, corrosion-proof and non-magnetic, these suit plain bearings and specialised ball bearings where weight, quiet running or resistance to chemicals matters more than outright load.
• Rubber - Buna: A nitrile rubber used for contact seals to keep grease in and contamination out.

Accu’s bearings are supplied in their natural finish, with the material itself providing the running surface rather than an applied coating.

Sizes and Types of Bearings Available

Accu’s range of bearings suit a wide array of precision engineering applications, the nature of which determines which form factor or features are most appropriate. 

For general rotary duty, deep groove ball bearings are the versatile all-rounder, carrying radial and light axial loads at speed, with miniature ball bearings covering the smallest, most space-critical assemblies. Thin-section ball bearings boast low profile raceway walls, while flanged ball bearings add an integral mounting flange that locates the bearing axially without a separate housing.

Where a design needs combined radial and bidirectional axial load in one position, double row ball bearings use two rows of balls in an angular contact layout. Double row thin section ball bearings deliver that same capability in a deliberately slim cross-section for large-bore, weight-critical builds.

Beyond the ball ranges, needle roller bearings carry high radial loads in a compact cross-section for transmissions and gearboxes, supported by bearing inner rings that provide a hardened raceway where the shaft itself cannot serve as one. Thrust bearings handle pure axial load on vertical shafts and turntables and linear bearings convert that rolling principle into smooth straight-line travel along a shaft. 

For sliding rather than rolling motion, slide bearings and plate bearings are plain bearings, sometimes called bushings. Where a rolling bearing runs on balls or needles, a bushing offers a low-friction surface to slide against, which is the practical difference in the bushing versus bearing question. 

Sizes run from bores of around 1 mm in the miniature ranges up to 70 mm, with deep groove outside diameters reaching as far as 240 mm. Most rolling types are offered open, shielded (2Z) or sealed (2RS).

FAQs

Q: What exactly are bearings?

A: Bearings are components that let one part move against another with as little friction as possible while carrying a load between them. Most reduce friction in one of two ways: a rolling bearing runs hardened balls or needles between an inner and outer race so the surfaces roll rather than rub, while a plain bearing or bushing provides a slippery surface for the parts to slide against. The payoff is smoother motion, less wear, less heat and quieter running, whether the part spins like a wheel or slides like a linear carriage.

Q: What are three types of bearings?

A: The three broad types are ball bearings, roller bearings and plain bearings. Ball bearings use spherical elements for general radial and light axial loads and are the most common choice. Roller bearings, including needle roller bearings, use cylindrical elements to carry heavier radial loads in a compact space. Plain bearings drop the rolling elements and rely on a low-friction sliding surface. Bearings are also grouped by the motion they serve, which is where thrust bearings for axial load and linear bearings for straight-line travel come in.

Q: What are the three rules for bearings?

A: There is no single official list, but most engineers understand these three fundamentals: keep them clean, keep them correctly lubricated and fit them properly. Contamination on the raceway, the wrong lubricant and careless fitting that forces load through the rolling elements are the quickest ways to shorten a bearing's life. Get those three right and a quality bearing will usually reach its rated life.

Q: What are the common mistakes when using bearings?

A: The most common are contamination, over-greasing and poor fitting. Dirt or swarf reaching the raceway, too much grease raising drag and temperature or hammering a bearing on rather than pressing it squarely through the correct ring will all cut its life short. Others include over-tightening or too much preload, mixing incompatible lubricants and ignoring shaft and housing tolerances so the fit ends up too tight or too loose. Most bearing failures trace back to one of these rather than to the bearing itself.

Q: Do bearings have to go clockwise?

A: No. A standard rolling bearing runs equally well in either direction, clockwise or anticlockwise, because the balls or rollers roll the same way whichever way the shaft turns. The only exception is a specialised one-way or clutch bearing, which is built to lock in one direction and free-wheel in the other. Accu's bearings are conventional bidirectional types, so they can be fitted without regard to the direction of rotation.

Bespoke Bearings Manufacture.

High precision, bespoke manufacture of Bearings to customer specification. State of the art facilities specialising in both small batch prototyping and large scale manufacture.