Agricultural Bearings for Farm Machinery

Agricultural bearings work in some of the hardest conditions in machinery. Tillage tools drag through wet soil and stones, combines run for long days in chaff and dust, balers and mowers wrap crop around their shafts, and most of these machines stand outside for months between seasons. Yet they come from a small set of types. Insert bearings in pillow block, flange and take-up housings carry most shafts. Deep groove ball bearings in the 6200 and 6300 series sit in gearboxes, wheels, fans and motors. Tapered roller bearings carry wheel hubs, and spherical roller bearings carry the heaviest shafts. Below we cover where each type goes on farm machinery, which of our products fit each position, sizes by shaft, sealing against soil and water, lubrication around the season, the usual failure causes and what to send with an inquiry.

Which bearing goes where on agricultural equipment

Makers that serve agriculture divide the field the same way: soil working, seeding, hay and silage making, baling and harvesting [2]. Each group has its own load and its own dirt.

Machine and position	Load and conditions	Usual bearing
Disc harrows and disc tillers, disc gangs	Heavy shock, soil, stones, water	Special disc harrow bearings with square or round bores and multi-lip seals
Tillage tool shafts, rollers and packers	Shock and radial load, mud	UCP pillow blocks and UCF flange units with set screw inserts
Seed drills and planters, drive and metering shafts	Light load, dust, fertilizer	UCF and UCFL flange units, SB and SA inserts, 6200 bearings
Mowers, rakes and tedders	High speed, grass and stones	Ball bearings to the machine maker’s design; mounted units on drive shafts
Balers, pick-up and drive shafts	Continuous running, crop wrap, dust	Mounted units; hex bore inserts on hex shafts
Combine harvesters, augers, elevators, straw walkers, fans	Dust and chaff, long running hours in season	UCP, UCF, UCFL and UCT units; 6200 and 6300 bearings
Combine rotors, threshing drums and heavy shafts	Higher load, some misalignment	Spherical roller bearings, to the machine maker’s design
Implement and trailer wheel hubs	Radial and axial load, road shock	Tapered roller bearings in pairs, metric or inch
PTO gearboxes and rotary tiller gearboxes	Gear loads, oil lubrication	Tapered roller and deep groove ball bearings
Grain augers and farm conveyors	Radial load, thrust from the flights	UCP, UCF and UCT units
Grain dryer fans and motors	High speed, heat near the burner	6200 and 6300 deep groove ball bearings

Two points in this table matter more than the rest. First, mounted units do most of the work: much of the soil working and harvesting section of the NTN-SNR agriculture catalogue is given to insert bearings and their seals [2]. Second, the most specialised bearings on a farm machine, disc harrow bearings and hub units, are designed for one job and carry their own numbers. Treat them as separate parts when you replace them.

FULI products for farm machinery

These are the types on our product pages that cover farm machinery positions. Each category page lists the models on this site with their dimensions.

• Insert bearings. UC201 to UC214 with set screws, SA201 to SA210 with an eccentric collar and SB201 to SB208 with a narrower inner ring.
• Pillow block units. UCP204 to UCP212 plus UCP202, and inch bore pillow blocks for shafts in inches.
• Flange units. UCF204 to UCF213 four-bolt square flanges, UCFL204 to UCFL208 two-bolt oval flanges, and the 2-bolt flange bearing page.
• Take-up units. UCT206, UCT210 and UCT213 to UCT218 for shafts that need tensioning.
• Deep groove ball bearings. The 6200 series and 6300 series, open, ZZ or 2RS.
• Tapered roller bearings. Metric 302, 303, 320 and 322 series and inch sets such as L44649, LM11949 and 3780.
• Spherical roller bearings. 22205 to 22224 and 22308 to 22320, for heavy shafts, usually mounted in plummer block housings.

FULI also supplies square-bore and round-bore disc harrow bearings, ag hub units and KRRB-type inserts. They carry their own numbers, so send the model or a drawing and we confirm the exact part. The disc harrow bearing page lists common square and round bore sizes with their dimensions, and our article on types of hub bearings used in agricultural machinery explains how to tell a disc bearing, an insert and an ag hub unit apart.

Mounted unit sizes by shaft diameter

On most farm machines the shaft decides the insert, and the insert number fixes the bore. These are the metric sizes on this site, with the matching pillow block, flange, take-up and insert pages.

Shaft (mm)	Pillow block	Square flange	Oval flange	Insert, set screw	Insert, eccentric collar
20	UCP204	UCF204	UCFL204	UC204	SA204
25	UCP205	UCF205	UCFL205	UC205	SA205
30	UCP206	UCF206	UCFL206	UC206	SA206
35	UCP207	UCF207	UCFL207	UC207	SA207
40	UCP208	UCF208	UCFL208	UC208	SA208
45	UCP209	UCF209		UC209	SA209
50	UCP210	UCF210		UC210	SA210
55	UCP211	UCF211		UC211
60	UCP212	UCF212		UC212

Many machines built to North American drawings have inch shafts. Inch bore inserts use the same housings as the metric unit of the same size, and the number after the dash gives the bore in sixteenths of an inch, so UCP205-16 fits a 1 inch shaft and UCP208-24 fits a 1-1/2 inch shaft. The inch bore pillow block page lists them.

For augers, elevators and belts that need tensioning, the take-up bearing page lists UCT units such as UCT206 and UCT210. When you replace a unit, check the bolt spacing and centre height as well as the shaft, because housings of the same designation can differ between makers. The UCP 200 series cross reference and the UCF and UCFL cross reference list brand numbers for the same sizes.

Set screw, eccentric collar or hex bore

The insert is a sealed deep groove ball bearing with a spherical outer ring, so it lines up in the housing even when a farm frame is not perfectly true. The locking method is what differs, and on farm machines it matters.

• Set screw inserts (UC, SB). Two grub screws lock the inner ring to the shaft. NTN-SNR notes that this type can run in both directions of rotation [2]. That makes it the usual choice on shafts that reverse, take shock or are driven by hand during setup.
• Eccentric collar inserts (SA). A collar on the extended inner ring is turned against an eccentric step until it grips. NTN-SNR states that the eccentric collar type works in one direction of rotation only [2]. Use it on shafts that always turn the same way, and turn the collar in the direction the shaft runs.
• Hex bore inserts. On balers and many implements the shaft is hexagonal, and the bearing bore matches it. NTN-SNR offers inserts with a hexagonal bore for balers [2]. Timken describes hex bore bearings as made for low speed, moderately loaded applications such as farm machinery and conveyors, and notes that no collars or set screws are needed to lock the inner ring to the hex shaft [1].

The insert bearing page compares the UC, SB and SA types with dimensions. The inserts listed on this site have a round bore. For hex shafts FULI supplies KRRB-type inserts, and for square gang shafts square-bore disc harrow bearings: send the model or a drawing and we confirm the exact part.

Sealing against soil, crop dust and water

Sealing decides the service life of most farm bearings. NTN describes the conditions in tillage plainly: field debris, dust and moisture cause many bearing failures every season [3]. In its test lab, disc harrow bearings were run inside a rotating drum filled to about 30% of its volume with a mixture of water and test dust, and bearings with triple-lip seals clearly outperformed bearings with standard single-lip seals [3].

The extra lips come at a price in speed. In the NTN-SNR seal comparison for insert bearings, a single-lip seal allows 100% of the bearing’s maximum speed, while the triple-lip seal for very polluted environments is rated at 30% [2]. Timken’s Tri-Ply seal bearings for tillage equipment carry a similar note: for speeds above 500 r/min, consult the maker [1]. So a heavy seal suits a slow disc gang or roller, not a fast fan shaft.

Fertilizer, slurry and silage juice also make some positions corrosive environments, not only dirty ones. There good sealing matters even more, and some makers offer coated or stainless units. Describe the conditions in the inquiry so the part can be matched to them.

NTN-SNR also warns that its reinforced agricultural inserts cannot be combined with every housing because of the seal [2]. The general lesson for any replacement: a wider seal or an extra shield can change how the insert sits in the housing, so compare the old part before ordering a different seal type.

The UC inserts on our product pages are sealed on both sides and greased, and the housings have a grease nipple for relubrication. If a position needs a different seal, an extra shield, end covers or a relubricatable version, tell us which seal and relube version you need in the inquiry, and we confirm the exact part before quoting.

Lubrication around the season

Farm machines are greased hard during the season and then parked. Both ends of that cycle affect the bearings.

1. Relubricate on schedule while the machine works. Fresh grease pushed in through the nipple flushes old grease and fine dirt out past the seal lips. Pump slowly until a little fresh grease appears at the seal, then stop, because too much grease adds heat and can push the seal out.
2. Grease before parking. A unit parked full of dirty grease and moisture corrodes over the winter. Clean the outside, grease the units and run the shafts briefly so the grease spreads.
3. Check the grease range. Buyers of machines for North America often specify a grease that works from −40 to 120 °C. If your machine has a required temperature range, write it in the inquiry and we will confirm a suitable grease.
4. Grease tapered bearings at assembly. Tapered roller bearings normally leave the factory with rust protection only and are rarely pre-greased. Pack them with grease when you assemble the hub.

For our sealed deep groove ball bearings, the default grease fill is about 30% of the free internal space. The bearing lubrication basics article covers relubrication quantities, and the grease fill calculator gives a figure for a given size.

Wheel hubs and gearboxes: axial and radial loads

Implement and trailer wheel hubs run on two tapered roller bearings, one inner and one outer, set facing each other. The pair carries the weight on the wheel and the side load when the machine turns or works on a slope. NTN-SNR lists metric tapered roller bearings such as the 30210 and 32011 to 32014 for soil working tools [2]. Metric hubs often use sizes such as 30206 and 30208. Hubs built to inch drawings use cone and cup sets such as L44649 and LM11949. Read the numbers on both the cone and the cup, and set the end play the machine maker gives when you assemble the hub. The how to choose wheel hub bearings article covers hub bearings in more detail. Some implements use a complete ag hub unit instead of loose tapered bearings; FULI supplies ag hub units, so send the hub number or a drawing and we confirm the exact part. The tractor itself is covered on the tractor bearing page: front wheel hubs, gearbox, PTO and differential.

PTO gearboxes and rotary tiller gearboxes commonly use tapered roller bearings on the shafts that carry axial load from helical or bevel gears, and deep groove ball bearings elsewhere. The gearbox bearing page covers this in detail. Heavier rotor and drum shafts may use spherical roller bearings such as 22210 and 22212, which accept some misalignment between the two ends of a long shaft.

Why farm machinery bearings fail early

1. Loose set screws. On mounted units, problems usually start at the set screws. If they are not tightened to the correct torque or loosen under shock and vibration, the inner ring turns on the shaft, wears the shaft and its own bore, heats up and fails. Tighten both screws to the specified torque and check them again after the first days of running.
2. Mud and water past the seals. Field debris, dust and moisture are the main enemies of tillage bearings [3]. Once these contaminants get past a worn or damaged seal they mix with the grease into an abrasive paste. High-pressure washing aimed at a seal can push water in the same way.
3. Moisture during storage. A machine parked outside with dirty grease in its bearings can be stiff or rough when the next season starts.
4. Wrong seal for the speed. Triple-lip seals are rated for a lower speed than single-lip seals [2]. On a fast shaft a heavy seal wears quickly and heats the unit.
5. Wrong end play in wheel hubs. Tapered bearings set too tight run hot; set too loose they hammer under road shock.
6. Misalignment between two units on one shaft. The spherical insert takes small errors, but a twisted frame or uneven mounting faces overload both bearings.
7. A missing prefix or suffix in the order. A bearing ordered without its full designation may have the wrong seal, bore or clearance for the position.

Because set screws and the housing fit decide how a mounted unit performs, our factory checks four things on mounted units before they ship: the housing mounting torque, the fit between insert and housing, the batch consistency of the centre height from the base, and the internal clearance of the insert.

How to write an agricultural bearing inquiry

An inquiry with these items can usually be priced in one round:

1. The full designation with every prefix and suffix, for example UCP208, UCF206, SA206, 6306-2RS or 30208. For tapered bearings, give both the cone and the cup number.
2. The quantity for each model.
3. The machine and position: disc gang, seed drill drive, baler pick-up, combine auger, wheel hub.
4. The shaft diameter and shape, round, hex or square, in millimetres or inches. For special parts, add the bore, OD and width.
5. For housings, the bolt spacing and centre height if you are replacing an existing unit.
6. The conditions: mud, water, washdown, speed and any temperature range.
7. A photo of the old unit and its markings, and any marking requirement. Rings can carry your authorized brand, the factory brand, or no brand.

Send your model numbers and quantities to sales@fuli-bearings.com or through the contact page. The quotation request template has a copy-ready format, and how to avoid ordering the wrong bearing lists the usual mistakes. We check each number against the standard designations, mark any item we cannot meet as an exception on the specification sheet rather than substituting it, and send the quote. An inspection report can cover dimensions, radial clearance, rotation noise, vibration, appearance, material certificate and batch traceability. Export documents are the commercial invoice, packing list and CCPIT certificate of origin, plus an FTA Form COO where the destination country qualifies.

Backed by 20+ years of bearing export experience in Linqing, Shandong. FULI ships to 50+ countries & regions.

Timken, NTN and SNR are trademarks of their respective owners. FULI is not affiliated with, authorized by or endorsed by any of them. Their published technical material is cited here as general reference only.

Sources

1. https://www.timken.com/wp-content/uploads/2018/04/Timken-Ball-Bearing-Catalog_10734.pdf
2. https://www.ntn-snr.com/sites/default/files/2021-07/DOC.I_AGRI_CAT3_GBa_web.pdf
3. https://help.bdsbearing.com/hubfs/Knowledge%20Base/NTN/NTN%20Agricultural%20Bearing%20Brochure.pdf