The Advantages of Thin Section Bearings

Advantages Explained

Kaydon thin section bearings reduce weight and friction, increase design flexibility and create more space as well provide precision running accuracy. 

Kaydon Reali-Slim® and Ultra-Slim® bearings provide the design engineer with many materials choices, various retainer and cross-section options. Kaydon Thin Section bearings can be designed with various internal fits, lubricants and material corrosion resistant options. 

As with any angular contact bearing Kaydon offers several contact angles. With bore sizes from 3/4 inch to 40 inches (19 mm to 1 m), Kaydon provides the largest range of thin section bearings in the Industry.

Kaydon YouTube Video “The Advantages of Thin Section Bearings.”

Kaydon Reali-Slim thin section bearings are lightweight and compact so they are perfect in situations where space is limited. They are available in three different bearing types: radial contact ball bearings (type C, fig. 1) angular contact ball bearings (type A, fig. 2) four-point contact ball bearings (type X, fig. 3).

In applications where dust or dirt or other contaminants are present, Kaydon Reali-Slim Thin Section bearings offer various seal options.

Kaydon bearings are often used as open when sealing is not required. The bearings can also be customized to meet specific application requirements.

Another advantage in using Kaydon Bearings is the ability to order matched pairs and or sets.

Contact your Pacific International Bearing when ordering matched pair angular contact ball bearings in different arrangements. Tandem arrangement (fig. 4), Back-to-back arrangement (fig. 5), Face-to-face arrangement (fig. 6), and four-point contact ball bearings.

These variations can provide multiple options to meet load, stiffness and accuracy requirements in the most efficient way.

In many applications, a single Reali-Slim four-point contact ball bearing can replace two bearings, compacting the design and simplifying the bearing mounting while saving space, weight, and cost. ​

Reali-Slim® thin section Kaydon bearings are designed to be a ready solution for highly demanding applications and for specific requirements in a wide range of applications.

Kaydon thin section bearings are utilized in aerospace, robotics, semiconductor, industrial machinery, machine tools, and medical device applications.

Reali-Slim open bearings are available in the following design series KAA, KA, KB, KC, KD, KF, and KG. These bearings are shown with their respective cross sections shown below.

Kaydon open bearings are intended for applications where bearings are not exposed to contaminants. Two popular series of the Kaydon open bearings are KA and KAA. In the part number you can easily determine the basic bore size for example KA020 has a 2.00 inch bore whereas KA025 has a bore size of 2.50 and so on through the product line.

Below is a list of the popular Kaydon bearing sizes:

Kaydon KA Type A (1/4″ cross-section) – Popular Sizes

Looking at the various series of thin section Kaydon bearings you can see the cross sections range from 3/16 inch wide for the KAA series to 1 inch wide for the KG series.

Kaydon created thin section bearings and created the standard using inch dimensions which was adapted by industry.

Kaydon started making standard thin-section bearings in 1954 based on inch sizes. The Kaydon Reali-Slim inch-standard bearing is the most widely used thin section bearing in the world.

Later on due to increased demand Kaydon developed metric thin section bearings for those applications that required metric denominations.

Kaydon needed to provide metric versions of the thin section bearings for dimensional compatibility with other components used internationally.

Kaydon through distributors like Pacific International Bearing offers the Kaydon Reali-Slim MM series of bearings.

Kaydon offers metric bearing as follows:

• ❚❚ in cross sections of 8, 13, and 20mm
• ❚❚ with bore diameters ranging from 20mm to 360mm
• ❚❚ with many of the same options found on standard

The Reali-Slim MM series can be customized for special applications using:

• ❚❚ ceramic balls
• ❚❚ special lubes
• ❚❚ integral seals

Kaydon Type an Angular Contact Series

Kaydon offers this deep groove ball bearing with a reduced shoulder on one side of the inner or outer race ball path. The design allows for a snap-over ball retainer assembly of a one-piece circular pocket ring type which yields a greater ball complement. This series bearings will accept radial load and single direction thrust load and will be used in conjunction with another bearing of similar construction. 

Type A Kaydon bearings require thrust loading to establish a contact angle. Stock products are single bearings and when purchased will need to be adjusted at installation to a specific running clearance or preload.

Kaydon offers matched spacers for applications requiring extra precision. In this series bearing part numbers reveal the dimensions for example K02508AR0 has a 25 mm bore and the K05008AR0 has a 50 mm bore and so on through all the Kaydon part numbers.

• Kaydon Reali‑Slim MM (8 mm cross-section) Type A – Popular Sizes

Kaydon bearings offer many options to help solve highly demanding applications and specific requirements in many different industries.

Reali-Slim thin section bearings have so many advantages based on weight and space savings and can be ordered in both inch and metric sizes.

With bore sizes from 3/4 inch to 40 inches (19 mm to 1 m), Kaydon easily has the largest range of thin-section bearings. 

FAQ

Q. What is a thin-section bearing?
A thin-section bearing is a ball bearing family with a constant cross-section (radial + axial thickness stays the same) while the bore (ID) changes. Inch series are KAA, KA, KB, KC, KD, KF, KG (3/16″ to 1″ sections). Metric MM series use 8, 13, or 20 mm sections across 20–360 mm bores.

Q. Why are thin-section bearings lighter than standard ball bearings?
Because ring mass scales ~linearly with mean diameter when cross-section is fixed:
​m≈ρ⋅A⋅πdm where A is the section area and dm​=(d+D)/2. Conventional bearings increase A as size grows; thin-section bearings keep A constant.

Q. Thin-section vs. crossed-roller bearings — which should I use?

• Thin-section ball: lower torque, higher speed, better for continuous rotation; great in robotic wrists, turntables, medical tools.
  
• Crossed-roller: higher tilt stiffness and accuracy in short-stroke rotary stages; lower speed.

Q. How do I do a quick thin-section bearing size check?

1. Choose the smallest section your envelope allows (e.g., KA 1/4″ or MM-8).
2. Select contact type (C/A/X) from your load vector.
   Compute speed factor n⋅dmn\cdot d_mn⋅dm​ to choose separator & lubricant.
3. Compute equivalent dynamic load P=XFr​+YFa​​ (use catalog X,Y,eX, Y, eX,Y,e).
4. Estimate life with ISO 281:L10​=(C/P)p×106, p=3 for balls.

Q. What is n⋅dmn\cdot d_mn⋅dm​ and why does it matter?
It’s the speed factor: rotational speed nnn times mean diameter dmd_mdm​. Higher ndmn d_mndm​ → higher heat and cage/grease shear → choose low-torque separators (formed-wire or PEEK circular-pocket) and low-bleed grease or oil.

Q. How much grease should I put in a sealed thin-section bearing?
Typical initial fill = 20–35 % of free internal volume. Run-in at 30–60 % operating speed for 10–20 min to stabilize starting torque and temperature.

Q. What precision should I specify (ABEC/ISO)?

• ISO P5 (≈ ABEC 5) for most robotic wrists and precision turntables.
• ISO P4 (≈ ABEC 7) for metrology/optics or very high speed.
  Higher classes reduce radial/axial runout but demand tighter mounting tolerances.

Q. Best materials for thin-section bearings in corrosive or clean environments?

• Bearing steel (52100) for general duty.
• Stainless (440C or nitrogen-alloyed) for cleaning agents/humidity.
  Si₃N₄ hybrid balls when you need electrical insulation, low mass, or non-magnetic behavior.
  

Q. Best grease for cleanroom or medical devices?
PFPE-based greases (PTFE-thickened) for chemical inertness, low outgassing, and steam-cycle tolerance; pick viscosity from your ndmn d_mndm​ and temperature.

Q. Open vs. sealed thin-section bearings — which should I choose?

• Open: lowest torque, highest speed; rely on filtered housings and periodic relube
• Sealed: better contamination control and grease life; slightly higher torque. Sealed inch series (e.g., JA/JB/JG/JU/JHA) map to common KA/KC/KD/KF geometries.

Purchase Kaydon Reali-Slim® and Ultra-Slim® bearings in inch and metric dimensions from Pacific International Bearing Sales send us your questions to [email protected].