Bearing Maintenance Guide: Lubrication, Inspection & Failure Prevention

Industrial bearings are one of the most unsung components in a facility. When they're running well, nobody notices. When one fails, you can lose a conveyor, a motor, a pump — and whatever it costs to stop production while you fix it.

The good news is that most bearing failures are preventable. Industry data from Schaeffler and SKF consistently shows that the majority of premature bearing failures trace back to avoidable causes: wrong lubrication, poor installation, or ignoring early warning signs. This guide covers all of it — inspection, lubrication, cleaning, installation, removal and storage — written for the maintenance engineers, plant operators and tradespeople who are actually doing the work.

Why Bearings Fail — and What That Means for Maintenance

Before diving into procedures, it's worth understanding the failure modes you're defending against. Schaeffler's analysis of bearing failures across industrial applications points to lubrication issues as the single biggest cause — responsible for around one-third to one-half of all premature failures. SKF and NSK data broadly agrees. The full breakdown looks like this:

• Lubrication failure: wrong lubricant type, too much, too little, or degraded grease. The most common cause.
• Contamination: dirt, water, metal particles, or process fluids entering the bearing. A sustained condition that causes progressive abrasive wear.
• Improper installation: applying force to the wrong ring, misalignment, incorrect interference fit, or overheating during mounting.
• Misalignment: shaft-to-housing misalignment introduces uneven load distribution that accelerates fatigue — often overlooked because it doesn't cause immediate failure.
• Overloading: exceeding radial or axial load ratings, or running at excessive speed.
• Material defect or end of service life: relatively rare in quality bearings from reputable manufacturers.

The maintenance practices in this guide directly address the first four causes — the ones that are within your control. If you're getting recurring failures in the same position, work through this list systematically. The bearing rarely fails on its own; usually the system failed the bearing.

Bearing Inspection — What to Check and When

The goal of inspection is to catch deterioration before it becomes failure. The earlier you catch a problem, the more options you have: plan a controlled shutdown, order a replacement, avoid collateral damage to the shaft and housing.

Daily Checks (Running Equipment)

These are quick sensory checks that any operator can do while the machine is running:

• Listen: Unusual noise — grinding, squealing, rhythmic knocking — is an early warning. Bearings that have always run quietly should continue to do so.
• Feel (accessible points only): A hand on the bearing housing gives a rough temperature indication. If it's too hot to hold comfortably, it's running above 60°C — worth investigating with an IR thermometer. Do not touch rotating components.
• Smell: A burnt odour near a bearing housing is a reliable sign the bearing is running abnormally hot. Stop and investigate.

Weekly Checks

• Vibration: If you have a vibration pen or analyser, log readings for critical bearing positions and compare against your baseline. A step-change in amplitude is more meaningful than the absolute value.
• Seal and housing inspection: Look for grease leaking past seals, discolouration, or any sign of housing movement. Grease leaking outward is normal in some designs; grease contaminated with dirt or showing metal particles is not.
• IR temperature scan: A spot-check with an infrared thermometer across bearing positions takes minutes and builds a useful trend record. An increase of more than 10–15°C from baseline is worth acting on.

Monthly / Scheduled Maintenance Inspections

Full inspection is best done during planned maintenance windows when equipment can be stopped and partially disassembled if needed:

• Grease condition: Where accessible, extract a small sample of grease from the bearing. Fresh grease is uniform in colour and consistency. Grease that is dark, contains metal particles, smells burnt, or has separated (oil and thickener visible separately) should be treated as failed lubrication — the bearing needs cleaning and regreasing, and possibly replacement.
• Clearance and play: With the shaft stationary, check for axial and radial play beyond the bearing's rated clearance — a feeler gauge is the standard tool for measuring bearing end float and axial clearance. Excessive play beyond the manufacturer's tolerance indicates wear.
• Alignment check: On drive systems, verify shaft-to-shaft or shaft-to-housing alignment is within coupling or mounting tolerances. Misalignment shows up as uneven temperature across the bearing, unusual vibration patterns, and accelerated wear on one side of the raceway. For coupling alignment procedure and misalignment types, see the Flexible Coupling Guide.
• Fastener torque: Check housing bolts and end-cap fasteners to specification. Loose housings allow the outer ring to creep, which causes fretting and rapid housing bore wear.

Interpreting Bearing Noise

Noise is diagnostic. Different sounds point to different problems:

• Grinding or grating: Contamination inside the bearing, or metal-to-metal contact from failed lubrication. Stop the machine — continued operation risks rapid, catastrophic failure.
• High-pitched squealing: Usually insufficient lubrication, or grease that has hardened and is no longer providing a film. The bearing is running metal-to-metal in places.
• Rhythmic knocking (once per revolution or matching ball-pass frequency): A damaged rolling element or spalled raceway. This bearing needs replacement.
• General increase in noise level: Can indicate wear, contamination, or grease breakdown — worth logging and monitoring closely.

Bearing Lubrication — Getting It Right

Lubrication is where most bearing maintenance goes wrong — either by neglect or by overdoing it. This section covers everything: which bearings need lubrication, how much, what type, and how often.

Which Bearings Need Relubrication

Not all bearings need maintenance lubrication — this is one of the most common misunderstandings in workshops.

• Sealed bearings (suffix 2RS, RS, 2RSR, LLU): Have rubber contact seals on both sides. Factory-packed with grease for life. Do not regrease. The factory fill is precisely calculated for the bearing's geometry and service life — adding more grease forces it past the seal, attracts contamination, and can cause churning. When a sealed bearing wears out, replace it.
• Shielded bearings (suffix ZZ, 2Z, ZZS): Have metal shields rather than rubber seals. The shields are non-contact and technically removable, so the bearing can be repacked — but it's rarely worth the effort on a standard deep groove ball bearing. On larger, more expensive shielded bearings in critical applications, regreasing through a nipple or after shield removal is sometimes done.
• Open bearings (no suffix or suffix C, N for snap ring): Have no integral sealing and require full maintenance lubrication — periodic greasing or continuous oil lubrication depending on the application.

For open bearings in pillow block housings, plummer blocks, and custom bearing units, relubrication through a grease nipple is standard practice. Check the housing for a nipple before assuming the bearing is sealed for life. For more on bearing housing types, see our pillow block and bearing housing guide.

Choosing the Right Grease

Not all greases are interchangeable. Three things matter: base oil viscosity, NLGI grade, and thickener type.

• NLGI grade: Determines the grease's consistency (how stiff it is). NLGI 2 is the standard industrial grade — firm enough to stay in place, fluid enough to distribute around the bearing. NLGI 1 is used for low-temperature or centralised lubrication systems. NLGI 3 is used for high-temperature or high-speed applications where the grease must resist being flung out.
• Base oil viscosity: Must match the bearing's speed and load. High-speed, lightly-loaded bearings need lower-viscosity base oil. Slow, heavily-loaded bearings (like those in presses or conveyors) need higher-viscosity base oil. ISO VG grade is the standard measure of base oil viscosity — for a complete cross-reference of all 20 grades from VG 2 to VG 3200, see the ISO VG viscosity chart.
• Thickener type: Lithium complex is the most common industrial thickener — good temperature range (up to around 150°C), water resistance, and wide compatibility. Polyurea is increasingly common in motor and sealed bearings and offers excellent oxidation resistance and long life, but it is not compatible with most lithium-based greases.

For most open industrial bearings operating at normal temperatures and speeds, a lithium complex NLGI 2 EP (extreme pressure) grease is the correct starting point. For high-load, slow-speed applications — conveyors, chains, gearboxes — consider a moly-fortified EP grease. See our moly grease guide for detail on molybdenum disulphide applications. For the broader picture across all grease types, see our industrial grease types guide.

The Grease Mixing Trap

This is worth its own section because it's a genuine and common failure mode. Mixing incompatible greases — particularly lithium complex and polyurea — can cause the mixture to dramatically soften, lose its structure, and drain out of the bearing entirely. The result looks like under-lubrication failure, and it is — but the cause was the two greases reacting with each other.

Before regreasing any bearing, identify the grease currently in use. If in doubt, purge the old grease thoroughly before applying a different type. A grease compatibility chart from your lubricant supplier will show which combinations are safe. When you can't confirm compatibility, use the same type as what's already in there. See our industrial lubricants guide for compatibility reference information.

How Much Grease to Apply

Over-greasing is the single most common lubrication mistake in Australian workshops. Adding more grease than necessary does not improve bearing life — it shortens it. Here's what happens: excess grease has nowhere to go, so the rolling elements must push it out of the way on every revolution. This generates heat through churning, which accelerates grease degradation and can force the grease past the seals, leaving the bearing under-lubricated in the raceway and creating a contamination pathway.

The standard guidance is to fill approximately one-third of the bearing's free internal volume when regreasing. For a bearing in a housing with a grease nipple, pump grease slowly and stop when you see fresh grease appearing at the purge point or seal lip — not before, and not after. Allow the bearing to run for 20–30 minutes after greasing: any excess will self-expel through the seals, and the bearing will reach its optimal fill.

A rough practical guide for grease quantity in open pillow block bearings:

• Shaft diameter 20–40mm: approximately 5–10g (one to two short pumps of a standard grease gun)
• Shaft diameter 40–70mm: approximately 10–20g
• Shaft diameter 70–100mm: approximately 20–40g

Always defer to the equipment manufacturer's specification where it's available.

Relubrication Intervals

There's no universal answer to "how often should I grease my bearings?" — it depends on bearing type, size, speed, temperature, and environment. The SKF and FAG (Schaeffler) relubrication interval methods both use a speed factor — the product of the shaft speed in RPM and the bearing mean diameter in millimetres (n × dm) — as the basis for calculating a base interval, then apply corrections for temperature and operating conditions.

Rather than working through the full calculation, here's a practical table for grease-lubricated deep groove ball bearings in typical industrial conditions (standard load, clean environment, operating below 70°C):

Temperature correction: For every 15°C above 70°C, halve the interval. A bearing running at 85°C needs regreasing twice as often as the table above suggests. At 100°C, four times as often.

Environment correction: In wet, dusty, or corrosive environments, increase frequency by 30–50%. In very clean, stable environments, you may be able to extend beyond the table values — use condition monitoring data to guide this.

The shift away from fixed-interval schedules toward condition-based relubrication (using ultrasound to detect friction changes) is gaining ground in well-resourced maintenance programs. It eliminates both over-greasing (the most common mistake) and under-greasing (the most damaging). If you're managing a large number of bearings, it's worth investigating.

Cleaning Bearings

Bearings need cleaning when they've been contaminated, when you're changing grease types (to avoid incompatibility), or when they're being removed for inspection and reinstallation.

Cleaning Process

1. Remove visible contamination: Wipe away old grease and surface dirt with a lint-free cloth. Don't use rags that leave fibres in the bearing.
2. Soak in solvent: Place the bearing in mineral spirits, white spirit, or a purpose-made bearing cleaning solvent. Allow it to soak for 10–20 minutes to soften hardened grease. A second rinse in fresh solvent will leave the bearing clean.
3. Agitate gently: A soft brush (not a wire brush — too aggressive) helps dislodge grease from the cage and rolling elements. Keep the bearing submerged while brushing to prevent loosened contamination from depositing back on the raceway.
4. Blow dry: Use compressed air to remove solvent from the bearing. Do not spin the bearing with compressed air — restrain both rings while blowing. An unloaded bearing spun with compressed air can exceed its safe speed limit and suffer catastrophic failure.
5. Relubricate immediately: A clean, dry bearing will begin to rust within minutes. Apply grease or oil immediately after drying. Do not leave a clean bearing unlubricated.

What Not to Do

Do not use an ultrasonic cleaner on precision bearings. Despite being commonly recommended, ultrasonic cavitation creates micro-pitting on the raceway surface and rolling elements — tiny flat spots that increase noise, reduce service life, and compromise dimensional accuracy. This is a well-documented failure mode in precision spindle and machine tool bearings. For heavily contaminated bearings in non-precision applications, the trade-off may be acceptable, but as a general rule, avoid it.

Machine tools that rely on Morse taper tooling — drill presses, lathes, and mills — are particularly sensitive to spindle bearing condition. Worn spindle bearings produce runout that prevents a Morse taper shank from seating concentrically, causing vibration and inaccurate results even when the tooling itself is undamaged. See our Morse taper guide for taper dimensions, fitting procedure, and how to identify the correct taper size.

Do not use solvent degreasers that leave a residue incompatible with your target lubricant. Chlorinated solvents in particular can react with some greases.

Bearing Installation — The Right Method Every Time

Incorrect installation is responsible for a significant proportion of premature bearing failures. The common mistakes are applying force to the wrong ring, using excessive heat, and failing to verify alignment after mounting. Getting installation right is not difficult, but it requires the correct method and a bit of care.

The Core Rule: Force on the Rotating Ring

When mounting a bearing on a shaft with an interference fit, all installation force must be applied directly to the inner ring only — never transmitted through the rolling elements. Similarly, when pressing a bearing into a housing, force goes on the outer ring. Transmitting installation force through the rolling elements damages the raceway — it creates indentations (false brinelling) that produce noise and accelerate fatigue from day one.

This seems obvious, but it's violated every day in workshops that use a hammer directly on the bearing outer ring when mounting on a shaft, or press down on the inner ring when pressing into a housing.

Heat Method (Induction Heating) — Recommended for Shaft Mounting

Heating the bearing's inner ring causes it to expand slightly, allowing it to slide onto the shaft without force. Once cooled, the interference fit locks it in place. This is the cleanest installation method for medium to large bearings.

• Use an induction heater: Induction bearing heaters heat the inner ring evenly and quickly, typically in 2–5 minutes, without risk of hot spots. They're the professional standard for bearings above about 30mm bore.
• Maximum temperature: 120°C (250°F). Exceeding this permanently alters the steel's heat treatment and changes the bearing's internal clearance and hardness. Never use an open flame — it creates uncontrolled hot spots.
• Process: Set the induction heater to 100–110°C. Place the bearing on the heater, monitor temperature with a contact probe. Once at temperature, slide it onto the shaft immediately (it cools quickly — you have about 30–60 seconds). Push fully to the shoulder or stop and hold firmly while it cools to prevent it pulling back.
• For very large bearings: An oil bath at a controlled temperature is an alternative when an induction heater is not available.

Press Method — For Smaller Bearings or Housing Mounting

For smaller bearings (typically below 30–40mm bore), or when pressing a bearing into a housing bore, a hydraulic press with a correctly sized mounting sleeve is the standard method.

• Always use a mounting sleeve: The sleeve contacts only the ring being pressed — inner ring when mounting on a shaft, outer ring when pressing into a housing. Never use an open-ended tube that contacts both rings simultaneously.
• Apply force evenly: Press straight and parallel. An angled press will cock the bearing in the bore, which either damages the rolling elements during installation or creates misalignment in service.
• Verify fit after installation: The bearing should rotate smoothly by hand. Excessive drag suggests the fit has tightened the internal clearance — check that the correct tolerance was applied to the shaft and housing.

Cold Method — For Housing-to-Outer-Ring Mounting

For some applications, chilling the bearing in a freezer (or dry ice/alcohol bath for larger temperature differentials) contracts the outer ring, allowing it to slide into the housing without pressing. Maximum safe cooling temperature is approximately -50°C. Below this, metallurgical changes to the bearing steel can cause permanent dimensional instability.

One caution: condensation forms on a cold bearing very quickly. Protect the raceway from moisture immediately after installation — grease the bearing as soon as it's in position. For more on bearing pulling and removal tools, see our bearing puller guide.

Verifying Installation

After installation, spin the shaft by hand. A correctly installed bearing should run smoothly with no roughness or drag beyond what its clearance class would predict. If there's a grease nipple on the housing, apply the first lubrication charge now. Check alignment of the assembly before starting under load.

Bearing Removal — How to Pull a Bearing Without Damage

Removing a bearing for inspection or replacement requires the same basic rule as installation: pull on the ring that has the interference fit. On a shaft, that's the inner ring. In a housing, that's the outer ring.

Using a Bearing Puller

A mechanical or hydraulic bearing puller is the correct tool. The puller jaws engage behind the inner ring (or outer ring for housing removal), and force is applied through a centre screw bearing directly against the shaft end. This pulls the bearing off cleanly without bending the shaft or damaging the housing bore.

Common configurations:

• 2-jaw or 3-jaw external pullers: Standard for pulling bearings from shafts. Three jaws provide better stability for larger or tightly fitted bearings.
• Internal (blind bore) pullers: Used when the outer ring is trapped inside a housing with no external lip to pull against. The jaws expand inside the bore to grip.
• Hydraulic pullers: Provide significantly greater force for interference-fitted bearings on large shafts, without the risk of bending the shaft from eccentric pulling.

See our bearing puller guide for selection advice and technique. The AIMS bearing puller range covers two-jaw and three-jaw options for shafts up to 100mm.

Using Heat to Assist Removal

Gentle heat applied to the outer ring of a bearing in a housing (or the inner ring on a shaft, where accessible) reduces the interference and makes pulling significantly easier. Keep the heat below 100°C to avoid affecting the bearing's heat treatment. An induction heater is ideal; a heat gun is acceptable for field work.

Never apply heat to the shaft itself to try to "shrink" it away from the bearing — the shaft heats more slowly than the ring and often expands before the interference is reduced.

If You Don't Have a Puller

In an emergency, a bearing can sometimes be driven off a shaft using a soft drift (brass or aluminium) applied alternately around the inner ring — never at a single point. This applies uneven force and risks damage to the shaft shoulder, the bearing seat, and the new bearing you're about to install. It's a last resort, not a method. Buy the right puller.

Sealed vs Shielded vs Open Bearings — What Each Needs

Understanding the difference between these three configurations is fundamental to doing the right thing at maintenance time.

Sealed Bearings (2RS, RS, 2RSR, LLU, 2RZ)

Rubber contact seals on one or both sides. Factory-packed with precisely measured grease for the bearing's calculated service life. Do not regrease. Do not remove the seals. If you force grease past a rubber seal, you risk damaging the seal lip (eliminating contamination protection), overfilling the bearing (causing churning and heat), and voiding any warranty. When a sealed bearing reaches end of life — identified by noise, roughness, or heat — replace it. They're not worth rebuilding at standard industrial bearing prices.

Shielded Bearings (ZZ, 2Z, ZZS, DDU)

Metal shields rather than rubber seals. The shields are non-contact (they don't press against the inner ring), which reduces friction and is why shielded bearings are often preferred in high-speed applications. The shields can be removed with care using a fine pick — but should only be removed if you have a specific reason to regrease and are confident of getting the shield back into its snap groove cleanly. Incorrectly reseated shields create noise and vibration.

For most standard shielded deep groove ball bearings in industrial applications, treat them as maintenance-free. If the application genuinely requires periodic regreasing, specify an open bearing with a housing-mounted seal from the outset. For more on deep groove ball bearing selection, see our deep groove ball bearing guide.

Open Bearings

No integral sealing at all. All contamination protection comes from housing seals or labyrinth arrangements. Full lubrication maintenance is required — typically via grease nipple in the housing. These are the standard configuration for larger industrial bearings in pillow blocks, plummer blocks, and custom bearing units. The bearing housing guide covers housing selection and seal options in detail.

Bearing Storage — Protecting Stock Before Installation

Bearings in storage are still at risk. Incorrect storage causes corrosion, false brinelling (surface damage from vibration), and contamination — all before the bearing has done a day's work.

Correct Storage Conditions

• Store horizontally: Vertical storage for long periods allows grease to migrate away from the lower part of the bearing under gravity, leaving the raceway dry. Particularly important for larger bearings stored for extended periods.
• Original packaging: Bearings are packed with anti-corrosion VCI (volatile corrosion inhibitor) paper or wrap. Keep them in their original packaging until the moment of installation.
• Temperature and humidity: Store in a cool, dry, stable-temperature environment. Temperature cycling causes condensation — the enemy of bearing steel. Avoid locations near external walls, roofs, or doorways where temperature swings are pronounced.
• Away from vibration: Bearings stored on or near vibrating machinery can develop false brinelling — a form of fretting damage to the raceway from rolling element vibration without rotation. Store on shelving isolated from floor vibration where possible.
• Shelf life: Most manufacturers rate standard grease-packed bearings at 3 years from manufacture date under proper storage conditions. Check the bearing date code if you're unsure how long stock has been sitting. Bearings approaching or past the 3-year mark should be inspected carefully before installation.

Pre-Installation Check After Storage

Always inspect a bearing before installing it, even if it's just come out of a box. Spin it by hand. It should rotate smoothly with minimal resistance and no roughness or grating. If the grease feels very stiff or dry, or if there's any roughness, don't install it — particularly in a critical application where an early failure would be costly.

Common Bearing Maintenance Mistakes

In no particular order — the errors that come up most consistently in workshops and on forums:

1. Over-greasing: The most common mistake. Adding grease until it comes out the side is not the goal — it's the problem. Use the 1/3 fill rule and stop when fresh grease appears at the purge point.
2. Mixing incompatible greases: Specifically, mixing lithium complex (the standard) with polyurea (common in modern sealed motor bearings). The mixture softens dramatically, loses structure, and runs out of the bearing. Identify the grease type before adding any.
3. Applying the wrong installation force: Hitting the outer ring when mounting on a shaft, or pressing on the inner ring when mounting into a housing. Forces must travel through the mounting ring only.
4. Using an open flame to heat bearings: Creates uncontrolled hot spots, often well above 120°C, and risks discolouring and hardness loss in the steel. Use an induction heater.
5. Ignoring early warning signs: The cost of planned maintenance is almost always lower than the cost of unplanned failure. Grinding noise, heat elevation, and changed vibration are all warnings — act on them.
6. Regreasing sealed bearings: Forcing grease past rubber seals damages the seal, overfills the bearing, and achieves nothing. If a sealed bearing has failed, replace it.
7. Contaminated tools: A grease gun that hasn't been cleaned between grease types introduces incompatible lubricant. Keep grease guns labelled and dedicated to one grease type, or purge thoroughly before switching.
8. Over-tightening housing bolts: Clamping the housing too tightly distorts the bore, reduces the bearing's internal clearance, and causes the rolling elements to run under excessive preload. Tighten to the specified torque — no more.
9. Not checking alignment after installation: A correctly installed bearing in a misaligned drivetrain will fail faster than one that was imperfectly installed in a correctly aligned system. Alignment matters.
10. Skipping pre-installation inspection: Bearings can be damaged in transit or storage. A quick spin-check before installation takes 30 seconds and can prevent a costly pull-down within weeks.

When to Replace vs Carry On

This is always a judgement call, but there are some clear decision rules:

Replace the bearing if:

• Grinding or grating noise is present and doesn't resolve after lubrication
• Visual inspection shows pitting, spalling, cracking, cage damage, or significant scoring on the raceway or rolling elements
• The bearing has sustained an unexplained heat spike — even if it's running normally again
• Grease extracted from the bearing contains metal particles
• Vibration analysis shows elevated bearing defect frequencies (ball-pass frequencies on the inner or outer ring)
• The bearing has exceeded its calculated L10 service life for the application

Investigate before replacing if:

• Noise appeared after regreasing — could be temporary over-fill self-expelling
• Temperature increased — check alignment, lubrication, and load before condemning the bearing
• Vibration increased — rule out imbalance, looseness, and misalignment first

When replacing, always investigate the failure mode. If the new bearing fails in the same position within the same period, the cause is systemic — overload, misalignment, contamination ingress, or wrong bearing selection — not a coincidence. See our deep groove ball bearing guide and thrust bearing guide for selection guidance. For linear and sliding bearing maintenance, see our linear bearing guide. When ordering a replacement, use the AIMS Bearing Cross Reference Guide to match part numbers across SKF, NSK, NTN, FAG, Koyo, NACHI and other brands.

Bearing Maintenance by Application

A brief practical guide for the most common AIMS customer applications:

Electric Motors

Most motors use sealed deep groove ball bearings — maintenance-free for life in standard applications. Check for vibration and noise at scheduled intervals. Confirm bearing size from the motor nameplate or manufacturer data when ordering replacement. For motors with grease nipples (typically larger frames), use the motor manufacturer's specified grease — many specify polyurea, not lithium. Using the wrong type will cause a compatibility failure at the next regreasing. See also our bearing housing guide.

Conveyor Rollers and Idlers

High contamination environment. Inspect seals for damage at every maintenance window. Use sealed bearings where the application permits; where grease nipples are fitted, prioritise interval discipline in dusty or wet environments — contaminants enter through degraded seals and cause rapid abrasive wear. Consider IP-rated or stainless housings in washdown or corrosive environments.

Pumps and Fans

Critical equipment where unplanned failure is expensive. Establish baseline vibration readings when the pump is commissioned or rebuilt, and monitor against baseline. Pump bearings often run in high-temperature environments (motor heat + fluid heat) — apply the temperature correction to relubrication intervals. Thrust loading in single-stage pumps is often higher than it appears — verify the bearing's axial load rating is not being exceeded. See our thrust bearing guide for axial load selection.

Pillow Blocks and Plummer Blocks

The most common grease-nipple-equipped bearing unit in Australian industrial environments. Inspect the seal faces for grease leakage and contamination ingress. Check housing base bolts for looseness — pillow blocks in vibrating environments frequently work loose. Replace the insert (inner bearing unit) rather than the full housing when the bearing wears out. See our bearing housing guide for insert specifications.

Linear Guides and Rails

Linear bearings require regular lubrication (oil or grease as specified) and protection from contamination. Wiper seals at the carriage ends should be inspected for damage — a torn wiper on a linear guide allows contamination to enter the rail directly. See our linear bearing guide for maintenance intervals and lubrication specifications.

PPE for Bearing Maintenance

Bearing maintenance involves solvents, compressed air, heat, and sometimes hydraulic pressure. Minimum PPE requirements:

• Safety glasses: Mandatory when using solvents, compressed air, or any pressing/pulling operation. Chips, solvent spray, and grease can cause eye injury. See our safety glasses guide for Australian Standard-compliant options.
• Chemical-resistant gloves: When handling mineral spirits or solvent degreasers.
• Heat-resistant gloves: When handling heated bearings from an induction heater.

AIMS carries a full range of industrial greases and bearing pullers. For help selecting the right grease or puller for a specific application, contact our team — (02) 9773 0122.

Frequently Asked Questions

How often should industrial bearings be re-greased?

It depends on bearing size, speed, and operating temperature. As a general guide for deep groove ball bearings in clean industrial conditions below 70°C: small bearings (up to 50mm shaft) at low speed (below 1,500 RPM) need regreasing every 6–12 months; the same bearing at higher speed (1,500–3,000 RPM) every 3–6 months. Larger bearings and higher temperatures reduce the interval significantly — halve it for every 15°C above 70°C. The equipment manufacturer's recommendation always takes precedence over general tables.

How much grease should I put in a bearing?

Fill approximately one-third of the bearing's free internal space. In practice, for a pillow block with a grease nipple, pump slowly and stop when fresh grease appears at the purge seal or drain plug. Running the bearing for 20–30 minutes after regreasing allows excess to self-expel. Over-greasing is more common than under-greasing and causes heat buildup that shortens bearing life.

Can you mix different types of bearing grease?

No — not without confirming compatibility first. Mixing incompatible greases (particularly lithium complex and polyurea) can cause the mixture to dramatically soften, lose its structure, and drain out of the bearing. The failure looks like under-lubrication. Before regreasing, identify the grease currently in use. If you need to switch grease types, purge the old grease thoroughly first or use a dedicated grease gun for each type.

What are the warning signs that a bearing needs replacing?

Key indicators: grinding or grating noise that doesn't improve after lubrication; sustained increase in operating temperature; rhythmic knocking noise (often matching ball-pass frequency); visible spalling, pitting, or cracking on the raceway when the bearing is disassembled for inspection; grease contaminated with metal particles; or vibration analysis showing elevated bearing defect frequencies. Squealing often indicates insufficient lubrication — regrease first and monitor before condemning the bearing.

How do you clean industrial bearings?

Soak in mineral spirits or white spirit, agitate with a soft brush, then blow dry with compressed air — restraining the rings so they cannot spin freely under the air blast. Re-lubricate immediately after drying, as bare steel rusts very quickly. Do not use an ultrasonic cleaner on precision bearings — ultrasonic cavitation micro-pits the raceway surface and rolling elements, causing noise and accelerated wear.

Can you regrease a sealed bearing?

No. Sealed bearings (marked 2RS, RS, LLU) are factory-packed with precisely measured grease for their calculated service life. Forcing additional grease past the rubber seal damages the seal lip (removing contamination protection), overfills the bearing (causing churning and heat), and does not extend bearing life. When a sealed bearing wears out, replace it rather than attempting to regrease it.

What is the best grease for industrial bearings?

For most open industrial bearings operating at standard temperatures and speeds, a lithium complex NLGI 2 EP (extreme pressure) grease is the correct starting point. High-load, low-speed applications (conveyors, large presses) may benefit from a moly-fortified EP grease. High-temperature applications require a thickener with a higher dropping point — calcium sulphonate or polyurea grades. Always check the equipment manufacturer's specification first, and never mix grease types without verifying compatibility.

How do you install a bearing without damage?

For shaft mounting: heat the bearing to 100–120°C using an induction heater, then slide onto the shaft while hot. For smaller bearings or housing mounting: use a hydraulic press with a correctly sized mounting sleeve that contacts only the ring being pressed. Never transmit installation force through the rolling elements — apply force only to the ring with the interference fit. Never use an open flame to heat a bearing.

What causes most industrial bearing failures?

Lubrication issues are the leading cause — incorrect lubricant type, too much or too little, or degraded grease. Industry analyses (Schaeffler, SKF, NSK) consistently attribute between one-third and one-half of premature bearing failures to lubrication. Contamination is the second major cause, followed by incorrect installation and misalignment. Material defects in quality bearings are rare.

How do you remove a bearing without a bearing puller?

In an emergency, a bearing can be driven off a shaft using a soft drift (brass or aluminium) applied alternately around the inner ring in small, even increments — never at a single point. This risks damage to the shaft shoulder and bearing seat. It is a last resort, not a recommended method. For any regular maintenance work, invest in the correct puller — the shaft and housing damage from improvised removal typically costs far more than the tool.

What temperature should you heat a bearing to for installation?

Heat the bearing to 80–120°C for induction installation on a shaft. The practical target is around 100–110°C — enough to expand the inner ring for easy fitting, well within the safe limit. Never exceed 120°C (250°F), as higher temperatures permanently alter the bearing steel's heat treatment and internal clearance. Never use an open flame, which creates uncontrolled hot spots. An induction heater is the correct tool.

How long do industrial bearings last?

Service life depends on load, speed, lubrication quality, and installation — there is no single answer. Bearing manufacturers calculate L10 life (the operating hours at which 10% of a batch would be expected to fail under specified conditions). In well-maintained industrial applications with correct lubrication and installation, modern bearings from reputable manufacturers commonly achieve tens of thousands of hours of service. Poorly maintained bearings in the same position may fail in a fraction of that time.

What does a failing bearing sound like?

Grinding or grating indicates contamination inside the bearing or metal-to-metal contact from lubrication failure — stop the machine immediately. High-pitched squealing typically means insufficient lubrication. A rhythmic knocking or clicking, often corresponding to shaft speed or ball-pass frequency, indicates a damaged rolling element or spalled raceway. A general increase in noise level, or a change from the bearing's normal running sound, is worth investigating even if it doesn't fit a specific pattern.

What is the difference between shielded and sealed bearings for maintenance?

Sealed bearings (2RS) have rubber contact seals that press against the inner ring — they are fully sealed, have a lower speed rating than equivalent shielded bearings, and are maintenance-free for life. Shielded bearings (ZZ) have non-contact metal shields — they offer less contamination protection but run at higher speeds with less friction, and the shields can technically be removed for regreasing, though this is rarely done in practice. Neither type should be force-regreased without removing the shield or seal first.

What is NLGI grease grade and which should I use?

NLGI (National Lubricating Grease Institute) grade is a measure of grease consistency — how stiff it is. The scale runs from 000 (almost fluid) to 6 (very stiff). NLGI 2 is the standard industrial grade, suitable for most bearings operating in normal temperature ranges at moderate speeds. NLGI 1 is used in centralised lubrication systems and cold environments. NLGI 3 is used in high-temperature or high-speed applications where grease must resist being flung out. Check the equipment manufacturer's specification — most will call out NLGI 2 as the default.

For bearing retention components, also see the AIMS Circlips range — used to locate and secure bearings axially in housings and on shafts.

Need the right torque value? Our Metric Bolt Torque Chart covers every common grade and size.