THK RU User manual

Instruction Manual
No. 1038-T59006
Cross-Roller Ring
THK Linear Motion System

Table of Contents
iCross-Roller Ring
1. Introduction 1-1
1-1Acknowledgment ――――――――――――――――――――――――――― 1-1
1-2About this manual ――――――――――――――――――――――――――― 1-2
1-3How to use this product ―――――――――――――――――――――――― 1-3
1-4Product support ―――――――――――――――――――――――――――― 1-3
1-5Product and company information ―――――――――――――――――――― 1-3
2. Handling precautions 2-1
2-1Safety warning indications ――――――――――――――――――――――― 2-1
2-2Handling ――――――――――――――――――――――――――――――― 2-1
2-3Precautions on use ―――――――――――――――――――――――――― 2-2
2-4Lubrication ―――――――――――――――――――――――――――――― 2-3
2-5Storage ――――――――――――――――――――――――――――――― 2-3
2-6Disposal ――――――――――――――――――――――――――――――― 2-3
3. Installation3-1
3-1Installation procedure ――――――――――――――――――――――――― 3-1
3-2Recommended tightening torque for the presser flange and press bolts―――― 3-4
4. Lubrication4-1
4-1Greasing interval and quantity―――――――――――――――――――――― 4-1
4-2Lubrication method ―――――――――――――――――――――――――― 4-2

1-1
1. Introduction
Cross-Roller Ring
1-1Acknowledgment
Thank you for purchasing the THK Cross-Roller Ring. This manual describes precautions for use,
the installation method, and the lubrication method of the cross-roller ring.
The cross-roller ring is given an anti-rust treatment and sealed before being packaged. (Figure
1-1)
When storing the cross-roller ring, pack it as designated by THK and store it in a horizontal posi-
tion away from high or low temperatures and high humidity.
The packaging contains a Certificate of Inspection that guarantees the product quality. (Figure
1-2)
Please contact THK if you have any questions regarding quality.
1. Introduction
Figure 1-2: Certificate of
Inspection
Figure 1-1: Cross-roller ring packaging example

1-2
1. Introduction
Cross-Roller Ring
1-2About this manual
1-2-1 Target audience
Persons in charge of product assembly design, installation, maintenance, and persons who will
use this product.
1-2-2 Purpose
This manual describes correct handling methods and precautions for this product.
In order to achieve the maximum performance and a long service life from this product, read this
manual carefully, and use the product safely and correctly with a thorough understanding of the
contents of the manual.
If you will be printing this manual to read it, be sure to keep it where the target audience can refer
to it when needed.
1-2-3 Notices and points to remember
●Do not use or handle the product in ways that are not described in this manual.
●Do not reproduce, reprint, or lend the contents of this manual in whole or in part without
permission.
●Please note that the contents of this manual are subject to change in the future without prior
notice, due to product improvements or other reasons.
●We have made all possible efforts to ensure the accuracy of this manual’s contents. However,
if you find any mistakes or have any questions about this manual, please contact THK.
●Drawings show representative examples, which may differ from your product.
●Please understand that we are not responsible for any consequences resulting from the use
of this manual for any reason whatsoever.
●This manual can be applied to custom products. However, the details specified in the
specification drawings should take precedence over this manual.
* Custom products refer to products that have different materials and specifications from those
of the standard products in catalogs.

1-3
1. Introduction
Cross-Roller Ring
1-3 How to use this product
●This product must not be used for devices or systems that are utilized under situations that
may affect human life.
●Be sure to contact THK in advance if you are considering using this product for special appli-
cations, such as with devices or systems relating to passenger vehicles, medicine, aerospace,
nuclear power, or electric power.
●This product is manufactured under strict quality control. However, that does not mean that
the product is incapable of failure. For applications to equipment that may cause serious
accidents or loss as a result of the failure of this product, install safety devices or backup
devices that prevent such serious accidents or loss.
1-4 Product support
We have made all possible efforts to ensure the accuracy of this manual’s contents. However, if
you find any mistakes, please contact THK.
1-5 Product and company information
To find the most recent information about our products and company, we recommend that you
periodically visit our website.
●Website URL: http://www.thk.com/
●Technical Support Site (URL): https://tech.thk.com/

2-1
2. Precautions
Cross-Roller Ring
2. Handling precautions
2-1 Safety warning indications
This manual uses the following warning indications for matters involving safety. Be sure to obey
the text next to the warning indication, which contains important safety information.
Warning Incorrect handling may result in death or serious
injury.
Caution Incorrect handling may cause injury to a person
or property damage only.
Prohibited (Something that must not be done)
Required (Something that must be done)
2-2 Handling
CAUTION
Handling precautions
⿟Please use at least two people to move any product weighing 20 kg or more, or use a cart or
another method of conveyance. Otherwise, it may cause injury or damage the unit.
Do not disassemble
⿟Inner or outer rings that are split into two pieces are kept together by special rivets or by bolts
and nuts, so please install the product as-is. The improper installation of a spacer cage in a
cross-roller ring greatly impacts its rotational functionality. Please do not disassemble the
cross-roller ring.
Do not drop
⿟Take care not to drop or strike the cross-roller ring. Otherwise, it may cause injury or damage
the unit. Even if there is no outward indication of damage, a sudden impact could prevent the
unit from functioning properly.
Handling precautions
⿟Wear appropriate safety gear, such as protective gloves and safety shoes, when handling the
product.

2-2
2. Precautions
2. Handling precautions
Cross-Roller Ring
2-3 Precautions on use
CAUTION
Contaminant warning
⿟Prevent foreign materials, such as cutting chips or coolant, from entering the product. Failure
to do so could damage the product.
⿟Use a cover to prevent foreign materials such as cutting chips, coolant, corrosive solvents, or
water from getting in the product when it is used in an environment where such a thing is
likely.
Max. temperature
80℃
Max
⿟Do not use this product if the external temperature exceeds 80°C. If used above this
temperature, there is a risk that the resin and rubber parts may deform or become damaged.
Handling precautions
⿟If foreign materials such as cutting chips adhere to the product, replenish the lubricant after
cleaning the product.
⿟Slight oscillations can inhibit the formation of an oil film between the raceways and the area of
contact for the balls, resulting in fretting. We recommend periodically rotating the cross-roller
ring several times to help ensure that a film forms on the surfaces and rolling elements.
⿟Do not forcibly drive a pin, key, or any other positioning device into the product. This could
create indentations on the raceway and impair the product's function.
⿟Because it is possible that the seam for the inner or outer ring could be slightly off-center,
slightly loosen the bolts securing the inner or outer ring and correct with a plastic hammer
before inserting into the housing. (The securing rivets will adjust to the housing.)
⿟When installing the cross-roller ring onto a housing, if the inner ring is fixed, hammer the inner
ring to insert it. If the outer ring is fixed, hammer the outer ring. Hammering the non-fixed side
may cause damage to the unit.
⿟If the mounting material lacks sufficient rigidity or accuracy, the bearing load may be focused
in one area, and bearing functionality will dramatically decrease. Therefore, carefully consider
the rigidity and accuracy of the housing and base, and the strength of the securing bolts.
⿟Avoid applying force to the securing rivets or bolts when installing or removing.
⿟Be careful of the dimensional tolerances of the mounting components to ensure that the
presser flange firmly holds the inner and outer rings from the sides.

2-3
2. Precautions
2. Handling precautions
Cross-Roller Ring
2-4 Lubrication
CAUTION
Lubricant check
⿟Thoroughly wipe off anti-rust oil before using the product.
⿟Do not mix different lubricants. Even grease containing the same type of thickening agent
may, if mixed, interact negatively due to disparate additives or other ingredients.
⿟When using the product in locations exposed to constant vibrations or in special environments
such as in clean rooms, vacuums, and low/high temperatures, use a lubricant suitable for its
use/environment.
⿟Grease viscosity can vary depending on the temperature. Please keep in mind that the torque
of the cross-roller ring may be affected by changes in viscosity.
⿟Since the cross-roller ring unit contains high-quality lithium soap-based grease No. 2, you can
start using the product without replenishing grease. However, the product requires regular
lubrication, since it has a smaller internal space than ordinary roller bearings and because the
rollers need frequent lubrication due to their rolling contact structure. To replenish grease, it is
necessary to provide greasing holes that lead to the oil grooves formed on the inner and outer
rings. Regularly resupply grease of the same type so that it is distributed throughout the
interior of the bearing at least every three to six months. The final greasing interval/amount
should be set at the actual machine. When the bearing is filled up with grease, the initial
rotational torque temporarily increases. However, surplus grease will run off of the seals, and
the torque will return to a normal level after a short period of time. Because the thin type does
not have oil grooves, please lubricate by providing oil grooves on the inner diameter of the
housing.
⿟Excess grease may protrude from the outside edge of the cross-roller ring. The structure of
peripheral components will require careful consideration if contamination due to grease
around the edges of the device is a concern.
2-5 Storage
When storing the cross-roller ring, pack it as designated by THK and store it indoors in a
horizontal position away from high or low temperatures and high humidity. Please note that if the
product has been kept in storage for an extended period, the lubricant inside may have
deteriorated. Please ensure that you replenish the lubricant before using.
2-6 Disposal
The product should be treated as industrial waste and disposed of appropriately.

3-1
3. Installation
3. Installation
Cross-Roller Ring
3-1 Installation procedure
Follow the procedure below to install the cross-roller ring.
Preparing for installation
(1) Thoroughly clean the housing and other assembly parts, and make sure there are no burrs.
(2) If the seam of the split outer ring or inner ring is off-center, lightly adjust with a plastic hammer
before inserting. (If using the rivet type, insert as-is.)
Inserting the cross-roller ring onto a housing or shaft
Because the cross-roller ring is thin and can easily tilt when being inserted, use a plastic hammer
to tap the circumference a little at a time while inserting to keep it level. Continue to hammer
carefully until you hear the sound of it making direct contact with the reference surface.
Note) When inserting the inner ring, hammer the inner ring. When inserting the outer ring, hammer the outer ring.
Note) Oil holes are provided. Configure the ring to allow for direct replenishment of lubricant to all oil holes in
order to equally distribute lubricant throughout the internal space. (Install so that there is a short path to
the lubrication holes on the housing or rotating axis.)
図3-1.RB形 油穴
ハウジング
給脂穴
クロスローラーリング
油穴
Figure 3-1: Model RB oil hole
Housing lubrication hole
Cross-roller ring oil hole

3-2
3. Installation
3. Installation
Cross-Roller Ring
Mounting orientation for Models RU and RAU
Models RU and RAU have insertion holes for installing rollers in the outer ring. (Filler plugs are
attached.) Pay attention to the mounting orientation so that the filler plugs do not overlap with the
area under maximum load. (The periphery of the plugged section is slightly recessed, and a
fixing pin is driven into its side.)
Mounting orientation for Model RA-C
The outer ring of the Model RA-C is split to allow roller insertion.
When installing, pay attention to the mounting orientation so that the split section does not
overlap with the area under the maximum load.
(The split section is the part with two small holes next to the product name marking on the side
surface.)
Figure 3-2: Model RU plug
Figure 3-3: Model RA-C split section
Outer ring
Inner ring
Split section
Outer ring
Plug
Holes (marking side)

3-3
3. Installation
3. Installation
Cross-Roller Ring
Mounting the presser flange
(1) Mount the presser flange onto the single-piece ring (inner ring on Models RB and RA, outer
ring on the Model RE). In case of Models RU and RAU, mount the presser flange onto the
rotational axis side.
(2) After attaching the presser flange, align the mounting bolts while rotating the presser flange
several times. The same applies to the Model RU: align the mounting bolts while rotating
the presser flange several times.
(3) Install the press bolts. When manually turning the bolts, make sure they do not show
skewing caused by misalignment of the holes.
(4) Bolt tightening should be divided into three or four steps, from temporary tightening to final
tightening, moving diagonally between bolts in order. You can correct misalignment of the
split inner ring or outer ring when tightening by oscillating the single-piece outer ring or inner
ring back and forth (around 90°) four to five times each time you tighten a bolt.
Figure 3-4: Assembly order

3-4
3. Installation
3. Installation
Cross-Roller Ring
3-2
Recommended tightening torque for the presser flange and press bolts
Use a torque wrench to firmly tighten the press bolts so that there is no looseness. Table 3-1
gives the tightening torque for bolts with a tensile strength grade of 12.9 and a housing and
presser flange made of common medium-hard steel.
Table 3-1: Bolt tightening torque
Unit: N･m
Screw type Tightening Screw type Tightening
M 2 0.6 M 8 30
M 2.3 0.8 M 10 70
M 2.6 1.2 M 12 120
M 3 2 M 16 200
M 4 4 M 20 390
M 5 9 M 22 530
M 6 14

4-1
4. Lubrication
4. Lubrication
Cross-Roller Ring
It is necessary to provide adequate lubrication when using the cross-roller ring. Using the product
without lubrication may increase wear on the rolling elements and shorten the service life.
Lubricant has the following functions.
(1) Reducing wear on moving parts by lowering friction and preventing burns.
(2) Lengthens the rolling contact fatigue life by creating an oil film on the raceways, alleviating
stress.
(3) Prevents rust by creating an oil film on metal surfaces.
To optimize the performance of the cross-roller ring, the product must be lubricated according to
the usage conditions.
The mounting location of the grease nipple and pipe fitting must also be considered according to
the mounting orientation.
Even with a seal, the lubricant inside will be expelled slightly when running, so it is necessary to
set appropriate lubricant replenishment intervals according to the usage conditions.
4-1 Greasing interval and quantity
Grease lubrication
The greasing interval varies depending on the usage conditions and environment. In normal
conditions, even when rotation frequency is low, regularly resupply grease of the same type at
least every three to six months, distributing it throughout the interior of the product.
The final greasing interval/amount should be set at the actual machine.
Note) The standard models contain THK AFB-LF Grease (a lithium-based grease).
Oil lubrication
When lubricating with oil, the product will be shipped with VG68 oil. If using another type of
lubricant, please specify it when ordering.
zThe amount of lubrication will vary depending on the rotational speed and movement patterns.
In particular, if the rotation angle is small or if oscillatory movement is used, increase the
lubrication frequency or the amount of lubricant used. Adjust the lubrication frequency and use
the optimal amount of lubricant to create an oil film on the raceways.
zConfirm that lubricant is being discharged from the end of the lubrication pipe.

4-2
4. Lubrication
4. Lubrication
Cross-Roller Ring
4-2 Lubrication method
The cross-roller ring can be lubricated manually by using a grease gun or manual pump, or a
forced greasing method can be employed with an automatic pump.
The grease nipple and pipe fitting must also be installed in a location that is suited to the
mounting orientation in order to efficiently lubricate the product.
Manual lubricating method
The general method is to use a grease gun to replenish the lubricant periodically through the
grease nipple mounted on the cross-roller ring and housing.
Follow the procedure below to replenish the lubricant in the cross-roller ring.
(1) Replenish the grease inside the cross-roller ring with a grease gun.
(2) When replenishing grease, first supply the grease, rotate the product, and then supply more.
Continue this cycle of replenishing the grease and rotating the product multiple times to
distribute the grease throughout the inside of the product evenly.
Note) Do not immediately run the product at operating speed after greasing. Perform running-in operations at low
speeds. While running in, wipe off the excess grease that is expelled from the cross-roller ring. It is
recommended to perform the running-in process until grease is no longer expelled.
Forced greasing method
This method forcibly supplies a fixed amount of grease at a fixed interval using an automatic
pump, and recovery of grease is not done often. This requires lubrication design such as piping,
but it eliminates the possibility of running out of lubricant due to forgetting to replenish grease.

Appendix
Revision history
The instruction manual number is indicated on the back cover.
Date of issue Instruction manual No. Details
March 2022 No.1038-T59006 First version

No. 1038-T59006
Website URL: https://www.thk.com/eng/
Technical support site URL: https://tech.thk.com/
Inquiries