This is not a rare edge case. Counterfeit bearings are a documented problem across Indian industrial markets. Both SKF and Schaeffler have conducted raids in Mumbai, Kolkata and Chennai specifically to remove fake FAG, SKF and NTN units from the supply chain. A significant portion of premium branded bearings circulating through unverified channels in India are estimated to be counterfeit or substandard.

If you source bearings from an established, traceable supplier, you are largely protected. But if you have ever bought from an unknown trader, a low-price online listing, or a walk-in market stall, the checks below are worth running before the bearing goes onto the shaft.

Why Counterfeit Bearings Are a Serious Risk

Genuine industrial bearings are precision components. The steel grade, heat treatment, internal geometry, surface finish, cage material and lubrication quantity are all engineered together to meet a rated load capacity and service life. Counterfeit bearings compromise one or more of those elements typically the steel quality, the surface finish or the grease specification.

The consequences extend well beyond early bearing failure:

• Unplanned production downtime a conveyor, pump, gearbox or fan stops mid-shift
• Secondary damage a failed bearing damages the shaft, housing, seals and adjacent component-
• Safety risk high-speed or high-temperature applications can see catastrophic failure, not gradual wear
• Wasted maintenance spend the labour, replacement part and lost production together far exceed any saving on the original purchase

The real cost of a counterfeit bearing is almost never the bearing price. It is the machine it damages when it fails.

6 Checks You Can Run Before Fitting a Bearing

None of these checks require specialist instruments. They take a few minutes and can be carried out by any stores or maintenance team.

1. Start with the Outer Packaging

Genuine premium bearings SKF, FAG, NTN, NSK, TIMKEN and others are shipped in sturdy, consistently printed cartons. Check:

• Print quality: text should be sharp, consistent in weight and properly aligned. Blurring, smudging or inconsistent font weight is a warning sign
• Barcode: scan it if you have a reader. It should resolve to the correct manufacturer page or product. A barcode that returns nothing or a broken URL points to a problem
• Hologram or security sticker: most premium brands apply a hologram label to the carton. It should shift colour when tilted. A flat, non-shifting label is a copy
• Packaging weight and rigidity: genuine packaging uses good-quality card. Thin, flimsy or damp-feeling packaging is unusual for a brand-new bearing
• Language and spelling: genuine cartons printed for the Indian market carry correct English. Grammatical errors, awkward phrasing or inconsistent capitalisation suggest a reproduction

If the bearing arrived loose without any carton ask for the original packaging. A genuine distributor can always supply it.

2. Inspect the Engraving on the Bearing Ring

Genuine bearing manufacturers use laser engraving for the brand name, designation number and country of origin on the outer ring. Key things to look for:

• Depth and sharpness: laser engraving on a genuine bearing has clean, sharp edges. Characters stamped with a die or ink-printed rather than laser-engraved will look shallower, rougher or uneven under a magnifying glass
• Alignment: the text should follow the curvature of the ring consistently. Misaligned, drifting or unevenly spaced characters are a red flag
• Designation accuracy: the bearing number on the ring must match the number on the carton exactly including suffixes. A 6205-2RS and a 6205-2Z are different bearings; any mismatch between ring and box is a serious concern
• Brand logo sharpness: the SKF logo, the FAG lettering or the NTN mark on a genuine bearing is clean and consistently formed. A smudged, asymmetric or poorly proportioned logo should raise questions immediately

3. Check the Cage Material and Construction

The cage holds the rolling elements in position. Fake bearings frequently use the wrong cage material or an incorrect cage construction and this is one of the most reliable indicators of a counterfeit, because it is difficult to replicate correctly.

• Most standard industrial ball bearings use a single-piece stamped steel cage or a polyamide (nylon) moulded cage both are smooth, consistent and correctly proportioned. A two-piece riveted cage on a bearing that should have a one-piece design is a documented warning sign
• On larger bearings, a machined brass cage should look clean and precisely formed. Rough pocket edges, irregular spacing or surface porosity suggest a lower-quality manufacturing process
• Check that the cage sits centrally and moves evenly when you rotate the bearing. Excessive side-play or uneven movement points to poor dimensional control

4. Feel the Rotation and Listen for Noise

Hold the bearing and rotate the inner ring slowly by hand. A genuine bearing in new condition should feel:

• Smooth and consistent throughout one full rotation no rough patches, grinding or tight spots
• Slightly resistant from the grease not dry, and not so stiff that it resists hand pressure
• Quiet there should be no grinding, rattling, or clicking. A light swishing sound from the grease is normal; anything harder or irregular is not

A counterfeit bearing often has visibly more internal play than a genuine unit of the same designation. If you have a genuine bearing of the same type to compare against, the difference in rotation feel is often immediately apparent.

5. Check the Grease

Genuine bearings arrive with the correct quantity and grade of grease already applied by the manufacturer. Open-shield bearings (ZZ, Z) will have grease visible at the shield opening when new.

• Too little grease, dry rolling elements or an unusual colour (grey, black, bright orange instead of the typical amber, beige or off-white of standard lithium-based greases) can indicate that the bearing has been re-packed with non-specification lubricant
• An unusual smell acrid, solvent-like or burnt is worth noting
• For sealed bearings (2RS, RS), the seals should sit flush and evenly. A warped, displaced or misaligned seal means the bearing has been interfered with after manufacture

If in doubt about grease grade for your application, the bearing-grease page on this site covers the standard NLGI grades and temperature ranges in detail.

6. Verify Through the Brand Authentication Apps

All the major bearing brands whose products we stock have official mobile apps for counterfeit verification:

• SKF: SKF Authenticate app scan the QR code or barcode on the packaging
• Schaeffler (FAG / INA): OriginCheck app unique code on each carton
• NTN: Authenti Bear app for verification of NTN products
• NSK: NSK Verify code-based verification for precision bearings

If the bearing number returns no result, an error, or a result that does not match the packaging you are holding, stop. Do not fit the bearing. Contact your supplier and request a replacement with documented traceability.

The Highest-Risk Procurement Routes in India

Most counterfeit bearings in India enter the supply chain through a small number of predictable channels. Knowing these helps procurement teams apply scrutiny where it is most needed.

• Unverified online listings: prices that are 20–40% below typical distributor rates for a premium brand should prompt checks, not celebrations
• Open market traders with no documentation: in bearing markets like Nagdevi Street in Mumbai, legitimate authorised traders operate alongside grey-market ones. The difference is not visible on a display shelf it is in the supply chain documentation
• Bulk shipments without original inner packaging: genuine branded bearings arrive individually packed in manufacturer cartons. Bulk packs of loose bearings from secondary wholesalers carry higher risk
• No GST invoice or traceability documentation: a legitimate distributor can provide a GST invoice with the correct HSN code, and traceable supply documentation on request. If documentation is unavailable or incomplete, the bearing’s origin is unverifiable

What Traceable Supply Actually Means

Traceable supply means being able to follow the bearing back from your stores to the manufacturer through a documented chain of authorised distributors, import records and original manufacturer packaging.

At Pragati Enterprises, every branded bearing we supply comes in original manufacturer packaging with authentic markings. We hold stock from authorised channels and can provide GST-invoiced supply with documentation for procurement and audit requirements. We have operated this way since 1997 not because it is a marketing point, but because it is the only way to supply bearings into applications where failure has real consequences.

If You Suspect a Counterfeit

If you have already received or fitted a bearing you are not sure about, do not ignore it:

• Remove the bearing from service if it has not yet been fitted
• Keep the original packaging it is the primary evidence
• Photograph the bearing ring markings, cage, packaging and any labels
• Contact the brand’s India office through their official website with the photos and the supplier details
• Report the supplier to the manufacturer’s brand protection team all major brands have a counterfeit reporting channel

Continuing to run a suspected counterfeit bearing in a critical application is a risk not worth taking.

Sourcing Bearings You Can Trust

The simplest protection against counterfeit bearings is a supplier with a verifiable supply chain. If you are sourcing SKF, FAG, NTN, NSK, TIMKEN, KOYO or NACHI bearings and want to confirm what is currently in stock in Mumbai or need documentation for a procurement audit send us the bearing number and we will come back to you the same working day.

If you are sourcing SKF, FAG, NTN, NSK, TIMKEN, KOYO or NACHI bearings and want to confirm what is currently in stock in Mumbai or need documentation for a procurement audit send us the bearing number and we will come back to you the same working day.

Send us your bearing requirement →

A pillow block bearing is one of the easiest bearings in a plant to replace. It’s also one of the easiest to replace badly. A unit fitted onto a burred shaft, locked with guesswork torque and packed with grease at standstill can run hot within hours and fail within weeks.

This guide covers the full job for UC-series units (UCP, UCF, UCFL and UCT): identifying the replacement, removing the old unit, checking the shaft and base, locking the new insert, greasing it correctly and confirming it runs as it should. It’s written for fitters and maintenance engineers doing the work on site.

Before You Start: Identify Exactly What You Are Replacing

Read the marking on the housing and insert

Most pillow block units carry a cast marking on the housing and a stamped number on the insert. Take UCP 208 as an example:

• UC: an insert bearing with a wide inner ring, locked to the shaft by set screws
• P: the housing type, here a two-bolt pillow block
• 208: the size. From 04 upwards, multiply the last two digits by 5 to get the shaft diameter in mm, so 208 fits a 40 mm shaft. Sizes 01, 02 and 03 are 12, 15 and 17 mm.

The housing letters tell you how the unit mounts:

One point catches people out. A UCP 308 and a UCP 208 both fit a 40 mm shaft, but the 300 series is the heavier-duty range with a larger housing. The bolt centres and centre height are different, so one will not drop onto the other’s base. Match the full number, not just the bore.

The same applies across brands. UC-series units follow common dimensions, but a maker’s own ranges don’t always match them. SKF’s SY and FY units, for example, are not a direct swap for UCP and UCF housings. If you are changing brand or series, compare the centre height and bolt-hole centres before you order.

If the marking has worn off, measure the shaft diameter and the distance between the mounting-bolt holes. With those two numbers, a supplier can usually identify the unit.

Check how the insert locks to the shaft

Pillow block inserts are held on the shaft in one of three ways, and each is fitted differently:

• Set screw locking (UC series): two grub screws in the extended inner ring bear directly on the shaft. This is the most common type.
• Eccentric locking collar: a separate collar with an eccentric recess is turned onto a matching step on the inner ring, wedging the bearing to the shaft. It’s then secured with a single set screw. Makers use different designations for these inserts.
• Adapter sleeve (tapered-bore inserts, such as the UK series): a tapered sleeve and nut clamp the insert onto the shaft. These are common on larger shafts.

Replace like with like unless there is a clear reason to change. The locking method affects how the unit handles vibration, reversing loads and shaft condition.

Whole unit, or insert only?

If only the insert has failed and the housing is sound, you can replace the insert alone. If the housing is cracked, the bore is worn or the base has been distorted, replace the complete unit.

On site, most maintenance teams replace the complete unit. It costs little more than an insert, and it removes any doubt about a worn housing seat.

Tools and Parts to Have Ready

• The replacement unit or insert, checked against the old one before you start
• Hex keys for the set screws, and a torque wrench that reads in N·m
• A spanner or socket for the housing bolts, plus hardened washers
• A soft-faced (plastic or copper) hammer and, for eccentric collars, a drift punch
• A fine file or emery cloth, a clean rag and light machine oil
• A vernier caliper or micrometer to check the shaft
• A grease gun loaded with a compatible grease
• Shims, if the base needs levelling
• Lockout devices and tags for the drive

Step 1: Isolate the Machine and Make It Safe

Isolate the drive at its power source and apply a lock and tag before anyone works on the shaft. A conveyor or fan that restarts while a hand is near a bearing housing causes serious injuries.

Once the drive is isolated:

• Release belt or chain tension so the shaft is not under load.
• Support the shaft if removing the unit will leave it unsupported.
• Mark the position of the old unit on the base. A scribe line or paint mark makes it easier to refit the new one in the same place.

Step 2: Remove the Old Unit

1. Clean around the unit. Dirt knocked into an open housing or onto the shaft causes the next failure.
2. Release the locking.
   • Set screw inserts: back both set screws out fully.
   • Eccentric collars: loosen the collar’s set screw. Then tap the collar against the direction of rotation with a drift in its hole to free it.
   • Adapter sleeve units: bend back the lock washer tab and loosen the nut.
3. Unbolt the housing from the base.
4. Slide the unit off the shaft. If it resists, don’t hammer the housing or the inner ring. Set screws often leave raised burrs where they bit into the shaft, and those burrs are usually what stops the bearing from sliding off. Dress them down with a fine file or emery cloth, apply a little penetrating oil, and try again.

If the bearing has seized to the shaft, stop and assess the shaft before forcing anything. A shaft that has to be driven hard to release the bearing may need repair.

Step 3: Inspect the Shaft and the Mounting Base

This is the step most often skipped, and it’s the one that decides how long the new bearing lasts.

The shaft

• Is it straight? A bent shaft will overload any new bearing.
• Is it clean? It should be free of burrs, set screw marks and fretting (the rusty, dull patches left by movement between the inner ring and the shaft).
• Is the end chamfered? A lightly chamfered shaft end lets the insert slide on without catching.
• Is it the right size? Measure it at the bearing seat. Insert bearings normally run on a slightly loose fit. As an example, Asahi Seiko specifies a js7 tolerance for general use, which works out to about ±0.0125 mm on a 40 mm shaft. A shaft worn well undersize will let the inner ring creep, and a new bearing won’t cure that.

If the shaft is scored, worn or out of tolerance, repair or replace it. Otherwise, expect the new bearing to fail the same way.

The mounting base

The base must be rigid and flat, so that bolting the housing down doesn’t distort it. Asahi Seiko specifies a flatness of 0.1 mm or less for units up to a 65 mm shaft, and 0.15 mm for 70 mm and above. Check a painted or fabricated base with a straightedge. Shim it if necessary, but use full-length shims rather than small packers under one corner.

Step 4: Fit the New Unit onto the Shaft

1. Retract the set screws. Make sure the set screw tips don’t protrude into the bore before you slide the unit on. If they do, they’ll score the shaft on the way on.
2. Apply a light film of oil to the shaft.
3. Slide the unit into position slowly and squarely. Don’t let the shaft end strike the inner ring or the seal. Never hammer the inner ring, the seal or the flinger (the thin metal ring beside the seal). A hard knock can push the flinger into the seal. The unit then runs with extra drag, heat and noise from the first minute.
4. Fit the housing bolts with washers, finger-tight at first.
5. Align the unit. Rotate the shaft by hand and let the housing settle into line. With two or more units on one shaft, check they are square to the shaft and at the same height.
6. Tighten the housing bolts to the correct torque.

The same care applies after the bearing is on. If you later hammer a pulley or sprocket onto the shaft, the shock travels into the bearing and can cause the same seal damage. Press or draw drive components on instead.

Step 5: Lock the Insert to the Shaft

Set screw inserts

Tighten both set screws evenly with a hex key. For inserts with two set screws:

1. Tighten the first screw to about half the recommended torque.
2. Tighten the second screw to full torque.
3. Go back and tighten the first screw to full torque.

Use the torque value published by the maker of the unit you are fitting. As an example, Asahi Seiko publishes the following values for its set screw inserts:

Source: Asahi Seiko instruction manual, insert bearing units (set screw type). Other makers publish different figures. NTN-SNR, for example, lists 5.5 N·m for its UCFL205. Always check the data for your brand.

More torque isn’t better. Over-tightened set screws can distort the inner ring, reduce running accuracy and crack the ring.

On shafts subject to heavy vibration, shock or axial load, makers recommend spotting the shaft where the set screws seat. You can grind a small flat, or drill a shallow dimple so the screw tip sits just below the shaft surface. A shouldered shaft with a locking nut is better still.

Eccentric locking collar inserts

1. Push the collar onto the shaft so its eccentric recess engages the matching step on the inner ring.
2. Turn the collar by hand in the direction the shaft rotates until it grips.
3. Put a drift punch in the collar’s hole and give it a firm tap with a soft hammer to lock it.
4. Tighten the collar’s set screw.

Turning the collar the wrong way is a common mistake. The collar can then work loose in service, and the bearing starts to creep on the shaft. On drives that run in both directions, lock the collar harder with the drift. Better still, use a shouldered shaft, or consider a different locking method.

Adapter sleeve units

Tapered-bore inserts are driven up their sleeve by tightening the nut. The bearing’s internal clearance is reduced as it moves up the taper, so follow the maker’s figure for how far to tighten the nut. Then lock the nut by bending a tab of the lock washer into a slot. Adapter sleeves are more common on the larger split housings covered in our guide to plummer blocks and adapter sleeves.

Step 6: Grease Correctly

Most UC inserts come pre-greased from the factory, so a new unit doesn’t need packing before it runs. Where the housing has a grease nipple, the aim is to top up the bearing over its life, not to fill the housing on day one.

• Use a compatible grease. Mixing grease types (for example, a lithium grease with a calcium or polyurea grease) can soften the mix and reduce protection. If you don’t know what’s in the bearing, use the maker’s recommended type. Our guide to choosing bearing grease explains NLGI grades and base types.
• Don’t pump in a large amount with the machine stopped. The pressure can lift the seals into the flinger, which causes overheating. Makers recommend greasing with the shaft turning slowly, or turning it by hand between shots.
• Grease in small shots. The amount per shot is small: Asahi Seiko lists about 1.4 g for a UC205, 3.9 g for a UC208 and 10 g for a UC212. If you can’t measure it, add grease until a little old grease appears at the seal lip, then stop.

How often to relubricate depends mostly on temperature and conditions. As a guide, Asahi Seiko publishes these intervals:

The spread in this table is the point. The same UCP 208 might need grease every three years in a clean packing hall, but every month on a hot, dusty, wet line. Wash-down areas and plants that stay humid for months need shorter intervals than a dry workshop.

Where moisture or corrosion is the main problem, stainless steel pillow block units are often a better answer than more frequent greasing. For high temperatures, heat-resistant bearings are built with larger internal clearance (C3 or C4) and a high-temperature grease.

Step 7: Run It and Check It

Don’t hand the machine back as soon as the bolts are tight.

1. Turn the shaft by hand. It should rotate smoothly, with no tight spots or rough patches.
2. Run it under power and listen. Touch a listening rod or a long screwdriver to the housing and put your ear to the handle. A healthy bearing gives a smooth, even hum. Grinding, clicking or a rhythmic knock means something is wrong with the fitting.
3. Check the temperature. Take readings on the housing with a contact or infrared thermometer. It’s normal for the temperature to rise at first. It usually levels off within 2 to 3 hours of starting. If it keeps climbing, or the housing gets too hot to touch, stop and check the alignment, the locking and the amount of grease.
4. Record the readings. A note of the temperature and noise at commissioning gives you something to compare against at the next inspection. That’s how you catch a failure early.

Five Mistakes That Shorten the Life of a New Pillow Block

1. Fitting onto a damaged shaft. Set screw burrs, fretting and wear will damage a new insert quickly.
2. Hammering the unit into place. A knock on the inner ring or flinger damages the seal before the bearing has turned once.
3. Guessing the set screw torque. Too loose and the insert creeps on the shaft. Too tight and the inner ring can crack.
4. Turning the eccentric collar the wrong way. A collar turned against the direction of rotation will work loose.
5. Over-greasing at standstill. Pumping grease into a stopped bearing blows out the seals and causes the overheating the grease was meant to prevent.

When Replacing the Bearing Won’t Fix the Problem

If the same position keeps failing, the bearing is usually a symptom, not the cause. Before fitting a third or fourth unit, check:

• Alignment: whether the units are in line and at the same height on a long shaft
• Belt or chain tension: over-tensioning puts a heavy radial load on the bearing nearest the drive
• Shaft condition: bend, wear or a loose fit at the bearing seat
• Base condition: a flexing base or loose foundation bolts
• Environment: water, dust or chemicals getting past a standard seal
• Duty: whether the load or speed is higher than the unit is rated for

Sometimes the right answer is a different product rather than the same one again: a heavier 300-series unit, a stainless or thermoplastic housing, a triple-lip seal, a heat-resistant insert, or a split plummer block for a larger shaft. If you’re not sure which applies, share the application details with your supplier before re-ordering.

Frequently Asked Questions

Can I replace just the insert bearing and keep the old housing?
Yes. If the housing is undamaged and its bore isn’t worn, you can fit a new insert into the old housing. Tilt the insert at right angles to the housing and enter it through the notch in the housing bore, making sure the outer ring’s locking pin sits in the notch. Then swing it into line. If the housing is cracked or distorted, replace the complete unit.

What torque should I use on pillow block set screws?
Use the value published by the maker of your unit, because it varies by brand and size. As an example, Asahi Seiko specifies 4.9 N·m for its UC204–UC206 inserts and 11.8 N·m for UC207–UC209, while NTN-SNR lists 5.5 N·m for its UCFL205. Don’t over-tighten, as this can crack the inner ring.

Which way do I turn an eccentric locking collar?
Turn it in the direction the shaft rotates when the machine runs. Turned the other way, it can loosen in service.

How much grease should I put in a pillow block bearing?
Less than most people expect. A new unit is already greased at the factory. When relubricating, add a small shot of a few grams, with the shaft turning slowly if it’s safe to do so. Stop when a little old grease appears at the seal.

Why is my new pillow block bearing running hot?
The usual causes are too much grease, a seal damaged during fitting, misalignment, an over-tightened housing on an uneven base, or excessive belt tension. A temperature rise that levels off within a few hours is normal. One that keeps climbing isn’t, so stop the machine and check.

Need a Replacement Unit?

Pragati Enterprises has supplied pillow block bearings from Nagdevi Street, Masjid Bunder, Mumbai since 1997. We stock UCP, UCF, UCFL and take-up units in SKF, FAG and NTN, alongside China-make options. We supply single pieces or bulk quantities with GST invoices, and dispatch within 24 hours.

Send us the marking from your old unit, or the shaft diameter and bolt-hole centres, along with the quantity you need. We’ll reply within 12 hours.

View our pillow block bearing range · Request a quote

A 6205, a 6205-2RS and a 6205-2RS-C3 all fit the same 25 mm shaft and the same 52 mm housing bore. They are not interchangeable in service. Fit the wrong one and the bearing may run hot, let water in, or seize on a shaft it was never meant to clamp onto.

This guide covers the bearing suffixes you’ll meet most often, how the main brands write them differently, and which swaps are safe when you can’t get the exact one.

Seals and shields

The most common suffixes, and the ones that matter most in a dirty or wet plant.

Here’s where brands diverge. The same double rubber-sealed bearing is written:

• 2RS1 or 2RSH by SKF
• 2RSR by FAG
• DDU by NSK
• LLU by NTN
• 2RS or 2RD by Koyo
• 2NSE by NACHI

They’re equivalent in function, though seal materials and the exact lip design differ. If you’re switching makes, treat them as equivalent for selection purposes and check the temperature rating if the position runs hot, because standard nitrile seals have a lower limit than the bearing itself.

The shield-versus-seal decision, in one line each:

• Shields add almost no friction and barely affect maximum speed, but they don’t stop water or fine dust.
• Seals stop both, at the cost of friction, running temperature and speed. They’re also greased for life, so you can’t relubricate through them.

Internal clearance

The second group that causes real trouble.

Internal clearance is the small amount of free movement inside an unmounted bearing. It sounds like slack, but it’s there so the bearing still has working clearance once it’s been pressed onto a shaft and has warmed up.

When you need more than normal:

• a tight interference fit on the shaft, which squeezes the inner ring and reduces clearance
• the bearing running hot, so the inner ring expands more than the outer
• some misalignment present
• heavy vibration

When you want less: positions needing precise location with minimal shaft movement.

The practical rule: if the old bearing was C3, fit C3. Substituting a normal-clearance bearing into a position specified as C3 is one of the more common causes of a replacement running hot within hours. Electric motors in particular are frequently C3 as standard.

Bore shape: the K suffix

A K after the number means a tapered bore, usually 1:12. These don’t go straight onto a plain shaft. They mount either on a tapered shaft seat or, far more often, on an adapter sleeve with a locknut.

Two things follow from that:

1. K and non-K are not interchangeable. A K bearing on a plain shaft has nothing clamping it.
2. The nut setting controls the clearance. Driving the bearing up the taper squeezes the inner ring and reduces internal clearance, which is why K bearings are usually specified C3 or C4. Tighten by the figure for the size, not by feel.

K30 indicates a 1:30 taper, used on some larger spherical roller bearings. It is not interchangeable with 1:12.

You’ll see K most often on self-aligning and spherical bearings, where sleeve mounting is standard in the larger sizes.

Internal design: E, EC, CA, CC

These indicate a modified internal design, usually meaning more or larger rolling elements and therefore higher load capacity than the older design of the same size.

• E or EC: reinforced design. Common on cylindrical roller and self-aligning bearings.
• CA, CC, CAC: cage and guidance variants on spherical roller bearings. CC generally indicates a pressed-steel cage with a guide ring; CA indicates a machined brass cage.

An E-design bearing is dimensionally the same as the non-E version, so it fits the same housing. In most cases it’s an upgrade, though check with the maker where preload or speed is critical.

Cages

• J: pressed-steel cage, the usual default
• M, MA, MB: machined brass cage, used at higher speeds, higher temperatures or under heavy vibration. MA and MB differ in whether the cage is guided by the outer or inner ring.
• TN9, TNG, TVH: moulded polyamide cage. Quiet and light, but with a temperature ceiling, typically around 120°C, and vulnerable to ageing in some oils.
• W33: an annular groove and three lubrication holes in the outer ring, letting grease reach the bearing through the housing. Common on spherical rollers in positions that are relubricated in service.

The cage is where a substitution can quietly go wrong. Swapping a brass-cage bearing for a polyamide one in a hot position will shorten its life, even though the bearing number otherwise matches.

Heat stabilisation: S0 to S4

Standard bearings are dimensionally stable to about 120°C. Above that, the rings can change size in service. Heat-stabilised bearings carry an S code indicating the temperature they’re stable to, rising through S0, S1, S2, S3 and S4.

If a position runs hot enough to need this, it usually also needs the right grease and greater clearance. The combination matters more than any one element. Our high temperature bearings page sets out the S codes against temperature.

Precision classes

P0 is normal, and P6, P5, P4 and P2 tighten progressively on running and dimensional accuracy. Standard industrial positions run fine on P0. Spindles, grinding machines and anything where runout shows in the finished product usually need P5 or better.

Paying for a class the application doesn’t need gains nothing. Specifying below what it needs shows up in the work.

Pairing and preload codes

On angular contact bearings you’ll see arrangement suffixes: DB back to back, DF face to face, DT tandem. These usually come with a preload class, light, medium or heavy, written differently by each maker.

Two bearings of the same number are not a matched pair. If the position needs one, order it as a set and say so.

Reading a full designation

Take 22216 EK W33 C3:

• 22216 — spherical roller bearing, 222 series, 80 mm bore
• E — reinforced internal design
• K — 1:12 tapered bore, for sleeve mounting
• W33 — lubrication groove and holes in the outer ring
• C3 — greater than normal internal clearance

Every one of those affects whether the bearing is right for the position. Only the first group tells you whether it fits.

Which substitutions are safe

Usually safe:

• a brand’s equivalent seal code for the same construction (2RS1 for DDU for LLU)
• an E-design bearing in place of the older design of the same number
• a higher precision class than specified, where the cost is acceptable

Usually not safe:

• normal clearance in place of C3, or the reverse
• a shielded bearing (ZZ) where the original was sealed (2RS), in a wet or dusty position
• K for non-K, in either direction
• polyamide cage in place of brass in a hot position
• one angular contact bearing in place of a matched pair

Needs checking: a sealed bearing in place of an open one at high speed, since the seal lowers the speed limit.

When the suffix has worn off

If you can read the basic number but not the suffix, work from the application:

• Was the old bearing sealed, shielded or open? Look at the bearing itself.
• Does the position run hot, or is the shaft fit tight? That points to C3.
• Is it on an adapter sleeve? Then it’s a K bore.
• Is the housing drilled for grease into the outer ring? That suggests W33.

The dimensions tell you the basic number, and our bearing size chart covers that. The old bearing itself tells you most of the rest.

FAQs

What’s the difference between 2RS and ZZ?
2RS has rubber contact seals on both sides, which keep out fine dust and moisture but add friction and lower the speed limit. ZZ has metal shields that don’t touch the inner ring, so friction stays low but protection is limited to coarse dust.

What does C3 mean, and do I need it?
C3 is greater than normal internal clearance. It’s needed where the bearing runs hot, has a tight shaft fit, or is in a position specified for it, such as many electric motors. If the old bearing was C3, fit C3.

Is 2RS1 the same as DDU?
Functionally yes. They’re the SKF and NSK codes for a double rubber-sealed bearing. Seal materials and lip design vary slightly, so check the temperature rating if the position runs hot.

Can I fit a K bearing on a straight shaft?
No. A K bearing has a tapered bore and needs either a tapered shaft seat or an adapter sleeve with a locknut to clamp it.