Rotary table bearings are the components that let a machine tool table turn with almost no wobble while still carrying heavy loads from every direction. They sit between the fixed base and the rotating platform, and they have to manage radial load, axial load, and tilting moment all at the same time, without losing accuracy.
Choosing the wrong type is one of the most common mistakes in machine tool design. A bearing that runs fine at low speed can overheat at high RPM, and a bearing built for pure axial load can fail quickly under a heavy overturning moment. This guide breaks down the main rotary table bearing types, what separates them, and where each one fits.
What Is a Rotary Table Bearing
A YRT rotary table bearing is a precision bearing designed for the outer ring to stay fixed while the inner ring rotates, or the reverse, depending on the mounting. Unlike a standard radial bearing, it is built to take combined loads: radial force, two-directional axial force, and tilting moment, in a single compact unit.
This combined-load capability is why rotary table bearings show up in CNC rotary tables, four-axis and five-axis machining centers, indexing heads, direct drive motors, rotary milling heads, and high-precision measuring equipment. Running accuracy in these applications is usually rated in precision grades such as P5, P4, and P2, with P2 reserved for the most demanding positioning tasks.
Main Types of Rotary Table Bearings
YRT Bearings
YRT bearings are the standard rotary table bearing and the most widely used type in this category. The design uses three rows of cylindrical rollers: two rows of axial rollers that handle load from both directions, and one row of radial rollers that manages radial force and tilting moment. This layout gives the bearing high rigidity and stable running accuracy even under heavy combined loads.
YRT bearings are the default choice for general CNC rotary tables, turntables, and swivel heads where speed requirements are moderate.
YRTS Bearings
YRTS bearings share the same basic structure as YRT bearings but are engineered for higher speed. The internal geometry is modified to reduce friction and heat buildup, which raises the limiting speed compared to a standard YRT unit. Grease selection matters here too, since high-speed operation puts more demand on lubrication stability across a wider temperature range.
This makes YRTS bearings a common upgrade for direct drive spindles and high-speed CNC rotary axes where a standard YRT bearing would run too hot.
YRTM and YRTSM Bearings
YRTM and YRTSM bearings take the YRT and YRTS platform and add an integrated angle measuring system. A steel scale is built into the bearing itself, which allows real-time monitoring and correction of rotational position. Positioning accuracy on these bearings can reach the arc-second range, which is important for applications where the table’s exact angle has to be verified continuously rather than assumed from the drive motor alone.
These bearings are typically specified for high-end multi-axis machining centers and measuring systems where positioning error has a direct impact on part accuracy.
ZKLDF Bearings
ZKLDF bearings take a different construction approach. Instead of cylindrical rollers, they use axial angular contact ball bearings with a 60-degree contact angle, built from an integral outer ring, two inner rings, and two sets of ball and cage assemblies. The ball-based design runs with lower friction than roller-based YRT or YRTS bearings, which gives ZKLDF bearings the highest speed capability in the rotary table bearing family.
They are usually chosen when a spindle or rotary axis needs to run faster than a roller-based bearing can comfortably support, while still holding combined radial, axial, and tilting moment loads.
Cross Roller Bearings as a Rotary Table Alternative
Cross roller bearings are not classified under the YRT or ZKLDF families, but they are frequently used on smaller or more compact rotary tables. Rollers are arranged in a 90-degree V-groove pattern, alternating direction row by row, so a single bearing handles radial load, axial load, and moment load together.
Because the design lets two half-rows of rollers fit in the space of a single row, cross roller bearings are a good fit where space is limited but high rigidity is still required, such as robot joints, smaller indexing tables, and rotary stages on measuring instruments. For larger diameter tables carrying heavier combined loads, YRT-family bearings generally hold the advantage in load capacity and thermal stability.
How to Choose the Right Rotary Table Bearing Type
A few factors to consider while choosing the Rotary Table Bearing.
Speed requirement. Standard YRT bearings suit moderate speeds. YRTS and ZKLDF bearings are built for higher RPM, with ZKLDF typically reaching the highest speeds due to its ball-based design.
Load type and direction. All four main types handle combined radial, axial, and moment loads, but the axial-to-radial capacity ratio varies slightly by series and size, so it’s worth checking the load rating table against the actual application load.
Positioning accuracy needs. If the application needs continuous angle feedback rather than relying purely on drive control, YRTM or YRTSM bearings with their built-in measuring scale are the better fit.
Available space. Compact rotary stages, smaller robotic joints, and space-limited housings often favor cross roller bearings, while larger CNC tables typically use the YRT family.
Operating temperature and lubrication. Higher-speed series depend more on correct grease selection, since friction at speed affects both accuracy and bearing life over time.
LYDL Bearing manufactures the full YRT, YRTS, YRTM and ZKLDF rotary table bearing range, along with cross roller bearings, for machine tool builders and precision equipment manufacturers.
Rotary Table Bearing Applications
Rotary table bearings appear across a wide range of precision machinery, including CNC rotary tables and four/five-axis machining centers, indexing heads and direct drive rotary motors, rotary milling, grinding, and honing heads, robotic joints and automation equipment, and measuring and testing instruments where angular accuracy is critical.
Frequently Asked Questions
What is the difference between YRT and YRTS bearings?
Both use the same three-row roller structure, but YRTS bearings are modified internally to run at higher speeds with lower friction than standard YRT bearings.
What does ZKLDF stand for in bearing terminology?
ZKLDF refers to axial angular contact ball bearings with a combined outer ring and dual inner ring design, used where higher rotational speed is needed compared to roller-based rotary table bearings.
Can cross roller bearings replace YRT bearings on a rotary table?
In smaller or space-limited applications, yes. For larger tables with heavier combined loads, YRT-family bearings usually offer better load capacity and thermal performance.
What precision grades are used for rotary table bearings?
Common grades are P5, P4, and P2, with P2 used for applications that demand the tightest running accuracy, such as high-end CNC machining centers.
Why would a machine need YRTM instead of standard YRT bearings?
YRTM bearings include a built-in angle-measuring scale, which allows real-time position feedback. This is useful when positioning accuracy needs to be verified continuously rather than inferred from the drive system alone.
