Disc Harrow Bearing

Disc harrow bearings with square or round bore: W208PPB5, W209PPB5, W211PPB3, W209PPB2 and GW211PPB2 sizes, how to measure, seals and relube types.

A disc harrow bearing carries a gang of discs on a square or round shaft and keeps soil, crop residue and water out while the gang turns through the field. Most of these bearings are single row ball bearings with wide inner rings, a spherical outside diameter that aligns in the hanger housing, and heavy multi-lip seals behind a steel shroud. Numbers such as W208PPB5, W209PPB5, W211PPB3, DS208TT5 and GW211PPB2 cover a large share of the disc harrows, disc tillers and disc plows in use. FULI supplies square-bore and round-bore disc harrow bearings: send the model or a drawing and we confirm the exact part. Below we cover where the bearing sits, square bore against round bore, sizes checked against two makers’ catalogues, how to measure an old bearing, seal and relube versions, the usual failure causes and what to send with an inquiry.

Where the bearing sits on a disc gang

On a disc harrow the discs are threaded onto a long gang shaft with spacer spools between them. A nut at the end clamps the stack, so discs, spools and shaft turn as one unit. Two or more bearings carry the gang, each held in a hanger housing or a flanged stamping bolted to the frame. Timken describes its Tri-Ply seal bearings as designed for severe contamination such as disk harrows, disk tillers and other seed preparation equipment [1].

The bearing in that position has a hard life:

Shock load. Each disc strikes stones and hard ground, and the frame transmits the impact straight to the bearing.
Axial load. The discs are set at an angle to the direction of travel, so the soil pushes the gang along its own axis as well as up and back.
Misalignment. Frames twist under load. The spherical outside diameter lets the outer ring swivel in the housing so the bearing is not pinched.
Dirt and water. The bearing runs close to the soil and is often covered in mud. NTN describes field debris, dust and moisture as the cause of many bearing failures in tillage equipment every season [8].
Low speed. A disc gang turns slowly. Timken’s Tri-Ply seal tables ask buyers to consult Timken for speeds above 500 r/min [1], which shows how far these bearings are from high-speed designs.

Disc plows (disc ploughs) carry each disc on its own spindle or hub instead of a common gang shaft. The bearing type there depends on the plow maker and the hub design. Read the number from the old part before ordering, because a disc plow bearing is not always the same part as a harrow gang bearing, even when the bore shape looks alike.

Square bore vs round bore

The bore shape follows the shaft. Both types are common, sometimes on the same machine.

Square bore. The bearing slides onto the square gang shaft. The flats drive the inner ring, so no set screw, collar or key is needed to stop it turning on the shaft. Square bore bearings are sized by the shaft they fit, measured across the flats: 1-1/8 in, 1-1/4 in and 1-1/2 in are typical. The inner ring is often wider than the outer ring; Timken notes that the extra inner ring width gives greater support on the shaft [1].

Round bore. The bearing fits a round shaft or the round end of a spindle and is located by the parts clamped against its inner ring. Round bore disc bearings are sized in millimetres or inches, for example 45 mm or 2-3/16 in (55.58 mm). NTN offers its flange disc units with square, round, and round with locking collar bore options [8].

Hex bore bearings follow the same idea as square bore bearings with a six-sided shaft. Timken describes hex bore bearings as made for low speed, moderately loaded applications such as farm machinery and conveyors, with no collars or set screws needed to lock the inner ring to the hex shaft [1]. In Timken’s numbering, KRRB marks a hex bore type with a spherical outside diameter. FULI supplies KRRB-type inserts: send the model or a drawing and we confirm the exact part.

Disc harrow bearing sizes, checked against two catalogues

The table lists five common disc harrow bearings. Each row appears in the Timken ball bearing catalogue [1] and in NTN’s Bearing Finder [2]–[6], and the main dimensions agree between the two. Square bore sizes are given by the shaft across the flats. B is the inner ring width and C the outer ring width. Where the two makers differ, it is by 0.05 mm or less: Timken gives the inner ring of the square bore 208 and 209 sizes as 36.53 mm (1.438 in), NTN as 36.500 mm (1.437 in). Timken lists a ring width tolerance of 0 to −0.12 mm, or 0 to −0.15 mm on the 211 sizes [1], so these differences sit inside the published tolerance.

Timken number	NTN number	Bore type	Shaft or bore	OD D (mm)	Inner ring B (mm)	Outer ring C (mm)	Relubricatable
W208PPB5	DS208TT5	Square	1-1/8 in (28.6 mm) across flats	80	36.53	18.00	No [1][2]
W209PPB5	DS209TT5	Square	1-1/4 in (31.8 mm) across flats	85	36.53	30.18	No [1][3]
W211PPB3	DS211TT3	Square	1-1/2 in (38.1 mm) across flats	100	33.34	33.34	No [1][4]
W209PPB2	DS209TT2	Round	45.00 mm	85	30.18	30.18	No [1]
GW211PPB2	DS211TTR2	Round	2-3/16 in (55.58 mm)	100	33.34	33.34	Yes [1]

Dimensions are taken from Timken’s Tri-Ply seal series tables, non-relubricatable type and relubricatable type [1], and checked against the NTN item pages [2]–[6]. The relubricatable mark for GW211PPB2 comes from Timken’s relubricatable table only [1]; the NTN page for DS211TTR2 does not state it. W211PPB2 and other sizes we could check in only one catalogue are left out of the table.

A note on the number itself. In Timken’s system the W prefix with PP2, PP3, PP5 and similar suffixes marks a Tri-Ply seal bearing, and B marks a spherical outside diameter [1]. The relubricatable Tri-Ply series carries a G in front, as in GW211PPB2 [1]. NTN lists its numbers, such as DS208TT5 and DS208TTR5, as heavy duty disc bearings [2][7]. These are each maker’s own codes. Two numbers with the same dimensions are not automatically the same in seal design or clearance.

Relube versions are not always the same size

It is easy to assume that the relubricatable version of a disc bearing is the sealed-for-life version with a grease hole added. Published data shows that this is not safe for the 208 square bore size. The non-relubricatable W208PPB5 and DS208TT5 have an 18.00 mm outer ring [1][2]. Timken’s relubricatable GW208PPB5 lists a 21.00 mm outer ring [1], and NTN’s relubricated DS208TTR5 lists 24.0 mm [7]. Same bore, same 80 mm OD, three different outer ring widths.

A wider outer ring may not fit the hanger or stamping built for the narrow one. If you are changing a sealed-for-life bearing for a greasable one, or the other way round, measure the housing seat and the old bearing first, and send both widths with the inquiry. Tell us which seal and relube version you need, and we confirm the part that matches before quoting.

How to measure an old disc harrow bearing

When the number on the shroud has worn off, five measurements and a photo usually identify the bearing.

Bore shape. Square, round or hex. Look at the shaft as well as the bearing; a worn square bore can look rounded at the corners.
Bore size. For a square or hex bore, measure across the flats, not across the corners, with a calliper. Convert to inches if the machine was built to inch drawings: 28.6 mm is 1-1/8 in, 31.8 mm is 1-1/4 in, 38.1 mm is 1-1/2 in. For a round bore, measure the diameter in two directions.
Outside diameter. Measure the outer ring at its widest point. A spherical OD is curved across its width, so measure at the centre line.
Inner ring width B and outer ring width C. Measure both. On many disc bearings the inner ring is wider than the outer ring and sticks out on both sides.
Grease fitting or hole. A grease hole in the outer ring, or a fitting on the housing that leads to the bearing, means the original was a relubricatable type.

Photograph the bearing from both faces and from the side, and include any marks on the shroud or the outer ring. The bearing size finder matches a measured bore, outside diameter and width to a number, and the bearing number decoder helps with partial markings.

Choosing the seal and relube version

Seal design matters more on a disc gang than on almost any other bearing on the farm. Timken’s Tri-Ply bearings use three rubber seals separated by steel spacers, or a one-piece moulded seal, with an outer shroud cap that protects the seals [1]. NTN’s disc harrow bearings use triple-lip seals, and NTN tested them in a rotating drum filled to about 30% of its volume with a mixture of water and test dust; bearings with triple-lip seals clearly outperformed bearings with standard single-lip seals [8].

Timken also offers R-Seal bearings with a single-lip contact seal and a metal shroud for planting, cultivating and harvesting machinery [1]. A single-lip design can suit a lighter position away from the soil, while a gang bearing that runs in mud needs the heavier seal.

On relubrication, the choice depends on how the machine is serviced:

Non-relubricatable. Filled with grease and sealed at the factory. No service, and no risk of grease pumped past the seal lips. The bearing is replaced when it wears.
Relubricatable. A grease path lets fresh grease flush out moisture and fine dirt. This works when operators grease the gangs regularly and slowly; pumping hard can lift a seal lip and let dirt in.

FULI supplies square-bore and round-bore disc harrow bearings, and seal and lubrication versions vary between makers and between machines. Tell us which seal and relube version you need, with the old number or the measurements, and we confirm the exact part.

Why disc harrow bearings fail early

Water and mud past the seals. Once dirt mixes with the grease it becomes an abrasive paste. NTN identifies seal durability as one of the major factors in bearing life in this environment [8].
A loose gang. If the gang bolt is not tight, the discs and spools move on the shaft. A square bore then hammers against the shaft flats and both wear quickly. Check the gang nut after the first hours of work.
The wrong width. A replacement with a different outer ring width, such as a relube version in a seat made for a non-relube one, can bind in the housing or leave the outer ring free to spin.
Over-greasing. On relubricatable bearings, too much grease or grease pumped too fast can push the seals out of place.
Damaged shroud. The steel shroud protects the seal from stones and roots. Once it is bent, the seal behind it wears quickly.
Storage. A harrow parked wet with mud packed around the bearings can start the next season with corroded rings.

What to send for a disc harrow bearing quote

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

The full number from the old bearing, with every prefix and suffix, for example W208PPB5, DS208TT5 or GW211PPB2.
The quantity for each number.
If the number is missing: bore shape, bore size across the flats or diameter, outside diameter, inner ring width B and outer ring width C.
The seal type you need, and whether the bearing must be relubricatable or not.
The housing or stamping if you are replacing a complete disc unit, with photos and the bolt spacing.
Any marking requirement. Rings can carry your authorized brand, the factory brand, or no brand.

Send your list to sales@fuli-bearings.com or through the contact page. We check each number against the published dimensions, mark anything we cannot match as an exception rather than substituting it, and confirm the exact part before quoting. The quotation request template has a copy-ready format.

The other bearings on a disc harrow and on most tillage tools are covered on the agricultural bearings page: pillow block and flange units on rollers and packers, tapered roller bearings in the transport wheels, and gearbox bearings. Our article on types of hub bearings used in agricultural machinery explains how to tell a disc bearing from an insert bearing and an ag hub unit. For round shafts with standard housings, see the insert bearing, pillow block bearing and flange bearing pages.

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

Timken, Tri-Ply, NTN and BCA 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

FAQ

What is the difference between a square bore and a round bore disc harrow bearing?

A square bore bearing slides onto the square gang shaft that runs through the discs and spools, so the shaft itself drives the inner ring and no set screws are needed. A round bore bearing fits a round shaft or the round end of a spindle and is held by the parts clamped against it. Both types usually have a spherical outside diameter so they can align in the hanger housing.

How do I measure a square bore disc harrow bearing?

Measure the square bore across the flats, not across the corners, and compare it with the shaft size in inches, for example 1-1/8 in (28.6 mm) for a W208PPB5 type. Then measure the outside diameter and the widths of the inner and outer rings. The inner ring of many disc bearings is wider than the outer ring.

Is a W208PPB5 the same as a DS208TT5?

In published catalogue data the two have the same main dimensions: a 1-1/8 in square bore, an 80 mm spherical outside diameter, an inner ring about 36.5 mm wide and an outer ring 18 mm wide. Seal design, clearance and lubrication can still differ between makers, so check those points against the original before you replace one with the other.

Are relubricatable disc harrow bearings the same size as sealed-for-life ones?

Not always. Published data for the 208 square bore size shows a wider outer ring on the relubricatable versions than on the non-relubricatable one, and two makers list different widths for their relubricatable versions. Measure the old bearing, or send its full number, before you change from one type to the other.

Do you supply disc harrow bearings?

Yes. FULI supplies square-bore and round-bore disc harrow bearings. Send the model number from the old bearing, or a drawing with the bore shape, bore size, outside diameter and ring widths, and we confirm the exact part before quoting. Tell us which seal and which relube version you need.