Schaeffler Product catalogue - medias
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Yoke type roller bearing track rollers, stud type roller bearing track rollers
 

Yoke and stud type roller bearing track rollers:

 
 
  • are ready-to-fit needle or cylindrical roller bearings of single or double row design ➤ Figure 2 to ➤ Figure 14
  • are mounted on shafts or studs (yoke type track rollers) or supplied with a heavy-section roller stud with fixing thread and a mounting aid (stud type track rollers) ➤ Figure 1
  • have particularly thick-walled outer rings with a crowned outside surface ➤ section
  • can support high radial loads ➤ section
  • tolerate axial loads which are due to small misalignment defects, skewed running or temporary contact running impacts ➤ section
  • are available with or without an inner ring (yoke type track rollers)
  • are produced with or without axial guidance of the outer ring (stud type track rollers are always produced with axial guidance)
  • are open or sealed on both sides ➤ section
  • are not mounted in a housing bore, but are supported on a flat mating track ➤ Figure 1
  • can be adjusted to the mating track in the design with the eccentric collar, thus permitting, for example, larger manufacturing tolerances in the adjacent construction.
 
   

Figure 1
Double row stud type track roller supported on a flat mating track

Symbole/00016410_mei_in_0k_0k.gif  Mating track

 

imageref_23159036939_All.gif

 
 

Bearing design

 
 

This range of yoke type track rollers comprises bearings:

 
   
 

Stud type track rollers are available in the following designs:

 
   
 

Yoke type track rollers (general)

The bearings have thick‑walled outer rings and are mounted on shafts or studs

 

Yoke type track rollers are single or double row units mounted on shafts or studs ➤ Figure 2 to ➤ Figure 7. They comprise thick-walled outer rings with a profiled outside surface and needle roller and cage assemblies or full complement needle roller or cylindrical roller sets. Yoke type track rollers can support high radial loads as well as axial loads arising from slight misalignment and skewed running. The bearings are available with or without an inner ring, with or without axial guidance and in sealed or open versions.

 

Typical applications

 

Proven areas of application of these products include cam gears, bed ways, conveying equipment and linear guidance systems.

 
 

Outside surface profile of the outer ring

The outside surface is predominantly crowned

 

Bearings with a crowned outside surface are predominantly used in practice since skewing usually occurs relative to the mating track and edge stresses must be avoided.

 

Radius of curvature

 

The radius of curvature of the outside surface is R = 500 mm. In the case of series NNTR..-2ZL, the radius is indicated in the product table.

 
 

Yoke type track rollers NATR..-PP, NATV..-PP, NUTR and PWTR..-2RS have an outside surface with the optimised INA profile ➤ link . In yoke type track rollers with this curvature profile:

 
   
 

X-life premium quality

imageref_19964530187_All.gif   Series PWTR is supplied as an X-life design. Due to a modified material and the optimised raceway geometry of the outer rings, the basic rating life has been increased by up to 30%. The static and dynamic load carrying capacity has also been increased. At the same time, the stress placed on the mating track has been reduced as a result of the optimised surface profile and its improved surface quality.  

Lower operating costs, higher machine availability

 

In conclusion, these advantages improve the overall cost-efficiency of the bearing position significantly and thus bring about a sustainable increase in the efficiency of the machine and equipment.

 

Suffix XL

 

X-life yoke type track rollers include the suffix XL in the designation.

 
 

Yoke type track rollers without inner ring, without axial guidance

The raceway must be designed as a rolling bearing raceway

 

Yoke type track rollers RSTO and RNA22..-2RSR do not have an inner ring ➤ Figure 2. Depending on the design, yoke type track rollers are also available as sealed versions ➤ section . They are particularly compact but require a hardened and ground raceway on the shaft or stud. Series RSTO is not self-retaining, which means that the outer ring and the needle roller and cage assembly can be fitted independently of each other. This gives simplified mounting of the bearings.

 
imageref_17757187211_All.gif   The rolling elements are guided by the cage. These designs do not have axial guidance of the outer ring. Axial guidance of the outer ring and needle roller and cage assembly (for RSTO only) must be provided in the adjacent construction.  
   

Figure 2
Yoke type track rollers without inner ring, without axial guidance, open or sealed on both sides

Fr =  radial load
Fa =  axial load
Symbole/00016410_mei_in_0k_0k.gif  Open (RSTO)
Symbole/00016411_mei_in_0k_0k.gif  Contact seals (RNA22..-2RSR)

 

imageref_23159041163_All.gif

 
 

Yoke type track rollers with inner ring, without axial guidance

 

Yoke type track rollers STO and NA22..-2RSR have an inner ring ➤ Figure 3. Depending on the design, yoke type track rollers are also available as sealed versions ➤ section . Bearings with an inner ring are used if the shaft or stud does not have a hardened and ground raceway. Series STO is not self-retaining. This means that the outer ring, needle roller and cage assembly and the inner ring can be fitted independently of each other. This gives simplified mounting of the bearings.

 
imageref_17757187211_All.gif   The rolling elements are guided by the cage. These designs do not have axial guidance of the outer ring. Axial guidance of the outer ring and needle roller and cage assembly (for STO only) must be provided in the adjacent construction.  
   

Figure 3
Yoke type track rollers with inner ring, without axial guidance, open or sealed on both sides

Fr =  radial load
Fa =  axial load
Symbole/00016410_mei_in_0k_0k.gif  Open (STO)
Symbole/00016411_mei_in_0k_0k.gif  Contact seals (NA22..-2RSR)

 

imageref_23159043083_All.gif

 
 

Yoke type track rollers with inner ring, with axial guidance

 

Yoke type track rollers with an inner ring are used if the shaft or stud does not have a hardened and ground raceway.

 

Designs

 

The series NATR and NATR..-PP have a cage ➤ Figure 4. The series NATV and NATV..-PP have a full complement needle roller set, while yoke type track rollers NUTR have a full complement cylindrical roller set ➤ Figure 5 and ➤ Figure 6. Yoke type track rollers PWTR..-2RS and NNTR..-2ZL have a full complement cylindrical roller set and a central rib ➤ Figure 7. Depending on the design, yoke type track rollers are also available as sealed versions ➤ section .

 
imageref_17757187211_All.gif   Bearings without a cage have the largest possible number of rolling el­ements and therefore have particularly high load carrying capacity. Due to the kinematic conditions, however, the speeds achievable with these bearings are somewhat lower than those achievable with the cage-guided yoke type track rollers.  
 

Axial guidance of outer ring

The type of guidance is dependent on the series

 

In NATR and NATV, axial guidance is provided directly by contact washers, while in NATR..-PP and NATV..-PP this is provided by contact washers and plastic axial plain washers. In NUTR, the outer ring is guided by the rolling elements, in PWTR..-2RS and NNTR..-2ZL it is guided by the central rib and the rolling elements.

 
 

Corrosion protection

Corrosion protection by Corrotect

 

Series PWTR..-2RS-RR is protected against corrosion by the special Cr(VI)‑free coating Corrotect ➤ link . These bearings have the suffix RR.

 
   

Figure 4
Yoke type track rollers with inner ring, with cage, with axial guidance, open or sealed on both sides

Fr =  radial load
Fa =  axial load
Symbole/00016410_mei_in_0k_0k.gif  Gap seals (NATR)
Symbole/00016411_mei_in_0k_0k.gif  Plastic axial plain washers (NATR..-PP)

 

imageref_23072002187_All.gif

 
   

Figure 5
Yoke type track rollers with inner ring, full complement needle roller set, with axial guidance, open or sealed on both sides

Fr =  radial load
Fa =  axial load
Symbole/00016410_mei_in_0k_0k.gif  Gap seals (NATV)
Symbole/00016411_mei_in_0k_0k.gif  Plastic axial plain washers (NATV..-PP)

 

imageref_23159047691_All.gif

 
   

Figure 6
Yoke type track roller with inner ring, full complement cylindrical roller set, with axial guidance, sealed on both sides

Fr =  radial load
Fa =  axial load
Symbole/00016410_mei_in_0k_0k.gif  Labyrinth seals (NUTR)

 

imageref_23159049611_All.gif

 
   

Figure 7
Yoke type track rollers with inner ring, full complement cylindrical roller set, with central rib, with axial guidance, sealed on both sides

Fr =  radial load
Fa =  axial load
Symbole/00016410_mei_in_0k_0k.gif  Protected lip seals (PWTR..-2RS)
Symbole/00016411_mei_in_0k_0k.gif  Contact washers with lamellar ring (NNTR..-2ZL)

 

imageref_23159051531_All.gif

 
 

Stud type track rollers (general)

The bearings have thick‑walled outer rings and a heavy-section roller stud

 

Stud type track rollers are similar in their construction to single and double row yoke type track rollers with axial guidance, except that the raceway is formed by a heavy-section roller stud with a fixing thread and type-dependent mounting aid, and with a type-dependent relubrication facility. Due to the thick-walled outer ring with profiled outside surface and the rolling element set, they can support high radial loads as well as axial loads arising from slight misalignment and skewed running. The stud type track rollers are available with or without an eccentric collar ➤ Figure 8 to ➤ Figure 14.

 

Typical applications

 

Proven areas of application of these products include cam gears, bed ways, conveying equipment and linear guidance systems.

 
 

Outside surface profile of the outer ring

The outside surface is crowned

 

Stud type track rollers with a crowned outside surface are predominantly used since skewing usually occurs relative to the mating track and edge stresses must be avoided.

 

Radius of curvature

 

In series KR, the radius of curvature is R = 500 mm. The series KR..-PP, KRE..-PP, KRV..-PP, NUKR, NUKRE, PWKR..-2RS and PWKRE..-2RS have an outside surface with the optimised INA profile.

 
 

In stud type track rollers with the optimised INA profile:

 
   
 

X-life premium quality

imageref_19964530187_All.gif   Stud type track rollers PWKR(E) are supplied in the X-life design. Due to a modified material and the optimised raceway geometry of the outer rings, the basic rating life has been increased by up to 30%. The static and dynamic load carrying capacity has also been increased. At the same time, the stress placed on the mating track has been reduced as a result of the optimised surface profile and its improved surface quality.  

Lower operating costs, higher machine availability

 

In conclusion, these advantages improve the overall cost-efficiency of the bearing position significantly and thus bring about a sustainable increase in the efficiency of the machine and equipment.

 

Suffix XL

 

X-life stud type track rollers include the suffix XL in the designation.

 
 

Stud type track rollers without eccentric collar

 

Stud type track rollers without an eccentric collar do not have a defined adjustment facility in relation to the mating track on the adjacent construction
_dictid_A480_
in mounting of the bearings.

 

Designs

 

The series KR and KR..-PP have a cage, the design KRV..-PP has a full comp­lement needle roller set. Series NUKR has a full complement cylindrical roller set, series PWKR..-2RS has a full complement cylindrical roller set and a central rib ➤ Figure 8 to ➤ Figure 11.

 
imageref_17757187211_All.gif   Bearings without a cage have the largest possible number of rolling el­ements and therefore have particularly high load carrying capacity. Due to the kinematic conditions, however, the speeds achievable with these bearings are somewhat lower than those achievable with the cage-guided stud type track rollers.  
 

Axial guidance of outer ring

The type of guidance is dependent on the series

 

In KR, axial guidance is provided directly by the contact flange and contact washer, while in KR..-PP and KRV..-PP this is provided by plastic axial plain washers, the contact flange and contact washer ➤ Figure 8 and ➤ Figure 9. The outer rings of series NUKR and PWKR..-2RS are guided by the rolling elements and ribs ➤ Figure 10 and ➤ Figure 11.

 
 

Relubrication facility

imageref_17757187211_All.gif   Stud type track rollers KR16 and KR19 with a hexagonal socket cannot be relubricated, while stud type track rollers KR16 and KR19 with a mounting slot have a relubrication facility.  
 

Corrosion protection

Corrosion protection by Corrotect

 

Series PWKR(E)..-2RS-RR is protected against corrosion by the special Cr(VI)-free coating Corrotect ➤ link . These bearings have the suffix RR.

 
   

Figure 8
Stud type track roller without eccentric collar, with cage, sealed on both sides

Fr =  radial load
Fa =  axial load
Symbole/00016410_mei_in_0k_0k.gif  Plastic axial plain washers (for KR..-PP) or gap seals (for KR)

 

imageref_23159056907_All.gif

 
   

Figure 9
Stud type track roller without eccentric collar, full complement needle roller set, sealed on both sides

Fr =  radial load
Fa =  axial load
Symbole/00016410_mei_in_0k_0k.gif  Plastic axial plain washers (KRV..-PP)

 

imageref_23159058827_All.gif

 
   

Figure 10
Stud type track roller without eccentric collar, full complement cylindrical roller set, sealed on both sides

Fr =  radial load
Fa =  axial load
Symbole/00016410_mei_in_0k_0k.gif  Labyrinth seals (NUKR)

 

imageref_23159063051_All.gif

 
   

Figure 11
Stud type track roller without eccentric collar, full complement cylindrical roller set, with central rib, sealed on both sides

Fr =  radial load
Fa =  axial load
Symbole/00016410_mei_in_0k_0k.gif  Protected lip seals (PWKR..-2RS)

 

imageref_23159064971_All.gif

 
 

Stud type track rollers with eccentric collar

The bearings have a defined adjustment facility relative to the mating track

 

Designs with an eccentric collar can be adjusted by means of a hexagonal socket on the flanged or threaded side of the roller stud. The outer ring outside surface can thus be adjusted against the mating track. As a result, larger manufacturing tolerances can be tolerated in the adjacent construction. Furthermore, this gives improved load distribution when using several stud type track rollers and also allows preloaded linear systems to be easily realised.

 

Highest point of the eccentric collar

 

The highest point of the eccentric collar is indicated on the roller stud side, the eccentricity e is stated in the product tables. This is also the location of the radial relubrication holes, which should lie in the unloaded zone of the rolling contact.

 

Designs

 

Series KRE..-PP has a cage, NUKRE and PWKRE..-2RS have a full complement cylindrical roller set ➤ Figure 12 to ➤ Figure 14.

 
imageref_17757187211_All.gif   Bearings with a full complement cylindrical roller set have the largest poss­ible number of rolling elements
_dictid_N3640_
and therefore have particularly high load carrying capacity. Due to the kinematic conditions, however, the speeds achievable with these bearings are somewhat lower than those achievable with the cage-guided stud type track rollers.
 
 

Axial guidance of outer ring

The type of guidance is dependent on the series

 

In the series KRE..-PP, axial guidance is provided by the plastic axial plain washers, contact flange and contact washers. In NUKRE, the outer ring is guided axially by the rolling elements, in PWKRE axial guidance of the outer ring is provided by the central rib and rolling elements.

 
   

Figure 12
Stud type track roller with eccentric collar, with cage, sealed on both sides

Fr =  radial load
Fa =  axial load
Symbole/00016410_mei_in_0k_0k.gif  Plastic axial plain washers (KRE..-PP)

 

imageref_23159107595_All.gif

 
   

Figure 13
Stud type track roller with eccentric collar, full complement cylindrical roller set, sealed on both sides

Fr =  radial load
Fa =  axial load
Symbole/00016410_mei_in_0k_0k.gif  Labyrinth seals (NUKRE)

 

imageref_23159109515_All.gif

 
   

Figure 14
Stud type track roller with eccentric collar, full complement cylindrical roller set, with central rib, sealed on both sides

Fr =  radial load
Fa =  axial load
Symbole/00016410_mei_in_0k_0k.gif  Protected lip seals (PWKRE..‑2RS)

 

imageref_23159111435_All.gif

 
 

Optimised INA profile

 

The advantages of the optimised INA profile are:

 
   
 

Hertzian pressure curve

Optimised INA profile, profile R = 500, cylindrical profile

 

The Hertzian pressure curve is more favourable for bearings with an optimised INA profile than for bearings with a cylindrical profile or with a profile where R = 500 mm (load Cr w/Pr = 5) ➤ Figure 15.

 
   

Figure 15
Hertzian pressure curve

Symbole/00016410_mei_in_0k_0k.gif  Optimised INA profile
Symbole/00016411_mei_in_0k_0k.gif  Profile R = 500
Symbole/00016412_mei_in_0k_0k.gif  Cylindrical profile
Symbole/00016413_mei_in_0k_0k.gif  Untilted running, β = 0 mrad
Symbole/00016414_mei_in_0k_0k.gif  Tilted running, β = 3 mrad

 

imageref_22455726987_All.gif

 
 

Maximum Hertzian pressure

Reduced Hertzian pressure with optimised INA profile

 

The maximum Hertzian pressure is significantly lower for bearings with an optimised INA profile than for bearings with a cylindrical profile or with the profile R = 500 mm ➤ Figure 16.

 
   

Figure 16
Maximum Hertzian pressure, stud type track roller NUKR80, Fr = 13 800 N (Cr w/Pr = 5)

pH =  maximum Hertzian pressure
β =  tilt angle
Symbole/00016410_mei_in_0k_0k.gif  Optimised INA profile
Symbole/00016411_mei_in_0k_0k.gif  Profile R = 500
Symbole/00016412_mei_in_0k_0k.gif  Cylindrical profile

 

imageref_22455729163_All.gif

 
 

Basic rating life of mating track

Longer rating life of mating track

 

The rating life of the mating track is significantly longer for outer rings with an optimised INA profile than for bearings with the profile R = 500 mm ➤ Figure 17. Yoke type track rollers NUTR15 ➤ Figure 18 were used as comparative bearings.

 
   

Figure 17
Basic rating life of the mating track, track made from 42CrMo4 V, hardness 350 HV

L =  basic rating life in millions of overrolling motions
Fr =  radial load
Symbole/00016410_mei_in_0k_0k.gif  Optimised INA profile
Symbole/00016411_mei_in_0k_0k.gif  Profile R = 500

 

imageref_22455731339_All.gif

 
 

Wear of the mating track

Reduced wear of the mating track

 

The mating track wears to a lesser extent with the optimised INA profile ➤ Figure 18: mating track made from EN-GJS-500-7, mean value derived from several test runs after 360 000 overrolling motions.

 
   

Figure 18
Wear of the mating track, track made from EN-GJS-500-7

sw =  wear
Fr1 =  low radial load
Fr2 =  high radial load
Symbole/00016410_mei_in_0k_0k.gif  Optimised INA profile
Symbole/00016411_mei_in_0k_0k.gif  Profile R = 500

 

imageref_22455733515_All.gif

 
 

Mating track made from 58CrV4, mean value derived from several test runs after 800 000 overrolling motions ➤ Figure 19.

 
   

Figure 19
Wear of the mating track, track made from 58CrV4

sw =  wear
Fr1 =  low radial load
Fr2 =  high radial load
Symbole/00016410_mei_in_0k_0k.gif  Optimised INA profile
Symbole/00016411_mei_in_0k_0k.gif  Profile R = 500

 

imageref_22455737867_All.gif

 
 

Rigidity in outer ring contact

Radial deflection

 

The radial deflection of the outer ring and rolling element set is smaller for bearings with an optimised INA profile than for bearings with the profile R = 500 mm ➤ Figure 20. Example, yoke type track roller NUTR15.

 
   

Figure 20
Rigidity in outer ring contact

δr =  radial deflection
Fr =  radial load
Symbole/00016410_mei_in_0k_0k.gif  Optimised INA profile
Symbole/00016411_mei_in_0k_0k.gif  Profile R = 500

 

imageref_22455735691_All.gif

 
 

Corrosion protection by Corrotect

A Corrotect coating is often more economical than using corrosion-resistant steels

 

Track rollers are often subjected to aggressive media. In such applications, corrosion protection
_dictid_C2580_
is therefore a decisive factor in achieving a long operating life of the bearings. In principle, corrosion-resistant steels may be used here. In many applications, however, the application of a special coating using available Corrotect thin film coating technology is more cost‑effective and should therefore be queried in advance. The series PWTR..‑2RS-RR and PWKR(E)..-2RS-RR are therefore available with a Corrotect coating. These bearings have the suffix RR ➤ section . Other series are also available as a special design with high performance Corrotect systems, which are matched to the specific application.

 
imageref_17757187211_All.gif   Before Corrotect-coated units are used, the compatibility of the coating with the existing media should always be checked.  
 

Corrotect systems

Corrotect coating thicknesses

 

Corrotect methods are available which permit the application of an extremely thin coating and, as a result, do not need to be included in the bearing tolerance (0,5 μm to 3 μm or 2 μm to 5 μm). Increased demands on corrosion protection
_dictid_C2580_
can be fulfilled with increasing coating thicknesses or completely different Corrotect methods. In isolated cases, dimensional changes resulting from the coating must be taken into account in a further processing step.

 

Cr(VI)-free coatings

 

The current Corrotect systems are all free from Cr(VI), protect effectively against corrosion and, as a result, extend the useful life of the Schaeffler components ➤ Figure 21.

 
imageref_17757210635_All.gif   Further detailed information on the modular coating tool box and on the individual coating systems can be found in Technical Product Information ➤ TPI 186 “Higher Performance Capacity through the Use of Coatings”. This publication can be requested from Schaeffler.  
 

Fitting of Corrotect-coated bearings

Take account of larger tolerances

 

The tolerances are increased by the thickness of the coating. In order to reduce the press-in forces, the surface of the parts should be lightly greased for fitting.

 
   

Figure 21
Uncoated and coated stud type track roller in the salt spray test


 

imageref_22456456587_All.gif

 
 

Load carrying capacity

 

Suitable for high radial loads

 

The bearings can support high radial loads. Yoke or stud type track rollers with axial guidance tolerate axial loads which are due to slight misalignments, skewed running or temporary contact running impacts.

 
 

Installation as yoke or stud type track roller

 

If the yoke and stud type track rollers are used on a flat mating track, the outer rings undergo elastic deformation. Compared with rolling bearings supported in a housing bore, yoke and stud type track rollers therefore have the following characteristics:

 
 
  • modified load distribution in the bearing. This is taken into consideration by the effective basic load ratings Cr w and C0r w used in the calculation of the rating life.
  • bending stresses and reverse bending strengths in the outer ring. These are taken into consideration by the permissible effective radial loads Fr per and F0r per. The bending stresses and reverse bending strengths must not exceed the permissible strength values of the material.
 
 

Permissible radial load under dynamic loading

Cr w is valid

 

For rotating bearings under dynamic load, the effective basic dynamic load rating Cr w is used. Cr w is used to calculate the basic rating life.

 
imageref_17757187211_All.gif   The permissible dynamic radial load Fr per must not be exceeded. If a value for Fr per is not given, the effective basic dynamic load rating Cr w is used as a substitute. This basic load rating must also not be exceeded by the radial load present. If the basic static load rating C0r w is lower than the basic dynamic load rating Cr w, then C0r w applies.  
 

Permissible radial load under static loading

C0r w is valid

 

For bearings under static load, either stationary or with only infrequent rotary motion, the effective basic static load rating C0r w applies. C0r w is used to calculate the static load safety factor S0.

 
imageref_17757187211_All.gif   The permissible basic static radial load F0r per must not be exceeded. If a value for F0r per is not given, the effective basic static load rating C0r w is used as a substitute. This basic load rating must also not be exceeded by the radial load present. In addition to the permissible radial load of the bearing, the permissible radial load of the mating track must also be taken into consideration ➤ link .  
 

Angular misalignment

 
 

Skewed running

Additional axial load under skewed running

 

Skewed running leads to additional axial load on the rolling bearing and axial slippage in the rolling contact between the outer ring and mating track ➤ Figure 22. Depending on the skewed running angle α and the lubrication, wear can occur in these cases.

 
imageref_17757187211_All.gif   A complete loss of adhesive friction between the outer ring and raceway, with correspondingly severe wear, is to be expected with a skewed running angle α ≧ 1,4 · 10–4 · pH (°) or α ≧ 2,5 · 10–3 · pH (mrad).  
   
   

Figure 22
Skewed running

α =  skewed running angle

 

imageref_22456213643_All.gif

 
 

Tilting

Cylindrical outer ring

 

If tilting occurs during running, increased edge stresses occur, especially in yoke and stud type track rollers with cylindrical outer rings.

 

Crowned outer ring

 

Track rollers with a crowned outer ring are less sensitive to tilting and should therefore be used in preference.

 

Limits for tilting

 

In practice, track rollers with a cylindrical outside surface and a tilting angle of β > 0,1° (1,7 mrad) and for yoke and stud type track rollers wth a crowned outside surface and a tilting angle of β > 0,25° (4,4 mrad) have proved susceptible to damage ➤ Figure 23.

 
 

   

Figure 23
Tilting

β =  tilt angle

 

imageref_22456215563_All.gif

 
 

Lubrication

 
 

Two contact zones

 

Two contact zones must be lubricated and considered separately:

 
 
  • the rolling elements and rolling element raceway
  • the outside surface of the track roller and the mating track.
 
imageref_17757210635_All.gif   The contact zone between the rolling elements and the rolling element raceway is covered in the chapter Technical principles, Lubrication.  
 

Lubrication of the bearing

Greased with a lubricating grease to GA08

 

For yoke and stud type track rollers, a lithium complex soap grease with a mineral oil base and EP additives to GA08 is used. Yoke type track rollers can be lubricated via the inner ring, stud type track rollers have a type-dependent relubrication facility via the roller stud. Greases for initial greasing are listed in the chapter Lubrication ➤ Table . For relubrication, greases in accordance with ➤ Table 1 are suitable.

 
imageref_17757187211_All.gif   In stud type track rollers with an eccentric collar, the eccentric collar covers the radial lubrication hole in the shank. Relubrication must therefore be carried out via the end faces.  
   
Table 1
Arcanol rolling bearing greases for relubrication
 

Arcanol grease
Designation
to DIN 51825
Type of grease
Track roller
Load150
KP2N–20
Lithium soap grease
with mineral oil base
Yoke and stud type
roller bearing track rollers
Load220
KP2N–20
Lithium calcium soap grease with mineral oil base
Yoke and stud type
roller bearing track rollers
Multi3
KP3K–30
Lithium soap grease
with mineral oil base
Yoke and stud type
ball bearing track rollers

 
 

Lubrication of mating track

Suitable lubricants

 

For lubrication of the mating track, all lubricants suitable for rolling bearing lubrication may be used. However, there are applications in which the mating track must not be lubricated.

 
imageref_17757187211_All.gif   If the contact point cannot be lubricated, wear must be expected, especially under high loads and at high speeds.  

Oil lubrication

 

For oil lubrication, oils of type CLP to DIN 51517 are recommended.

 

Grease lubrication

 

For grease lubrication, lithium soap greases to DIN 51825 should be used. Relubrication intervals can only be determined under operating con­ditions. Relubrication must be carried out at the latest when fretting cor­rosion first occurs; this can be identified by a reddish discolouration of the mating track or the outer ring.

 

Solid lubricants and anti‑friction coatings

 

These substances are also suitable for lubrication. At high traverse or rotational speeds, however, they provide effective lubrication for a significantly shorter period than oil or grease lubrication.

 
 

Central lubrication system
_dictid_L3840_
for stud type track rollers

Connection adapter with rapid-fit connection cartridge

 

If a central lubrication
_dictid_C4740_
system is to be used, a patented central lubrication
_dictid_C4740_
adapter can be used to connect the standard roller stud of stud type track rollers with hexagonal sockets on both sides ➤ Figure 24. This connector comprises a connection adapter with a hexagonal end and a rapid-fit connection cartridge.

 
 

The connection adapter is connected to the roller stud on one end of the stud type track roller by replacing the funnel type lubrication nipple with the fitting cylinder. The hexagonal end prevents rotation of the adapter. The other end of the stud type track roller is closed off using the supplied funnel type lubrication nipple ➤ Figure 24.

 
   

Figure 24
Central lubrication adapter and funnel type lubrication nipple

Symbole/00016410_mei_in_0k_0k.gif  Connection adapter with M10× 1 internal thread
Symbole/00016411_mei_in_0k_0k.gif  Rapid-fit connection cartridge
Symbole/00016412_mei_in_0k_0k.gif  Fitting cylinder
Symbole/00016413_mei_in_0k_0k.gif  Funnel type lubrication nipple

 

imageref_22456217995_All.gif

 

Hard PA pipes should be used in preference

 

The connection adapter has an M10×1 internal thread. This is used for screw mounting and sealing of the rapid-fit connection cartridge. The cartridge gives firm retention and sealing of the plastic pipe. It is therefore not necessary to screw the pipe and adapter onto each other. Hard PA pipes should be used in preference. In this instance, the operating limits according to DIN 73378 and the manufacturer's guidance must be observed. The maximum excess pressure for pipes made from PA11 or PA12 is as follows at +23 °C: 31 bar to 62 bar. The maximum excess pressure when using other screw-in connectors is 80 bar.

 

Dimensions

 

For dimensions of the adapters ➤ Table 2 and ➤ Figure 25.

 
   
Table 2
Dimensions of adapter
 

Central
lubrication adapter
Dimensions
W
L
l1
l2
l3
For polyamide pipe to DIN 73378
Designation
max.
approx.
d1×snom
AP8 8
27
16
22
4
4×0,75
AP10 10
27
15
22
5
4×0,75
AP14 14
25
8
20
6
4×0,75

 
   

Figure 25
Dimensions of central lubrication
_dictid_C4740_
adapters


 

imageref_22456220171_All.gif

 
 

Calculation of relubrication intervals

Simplified determination of lubrication impulses

 

The relubrication quantities for central lubrication
_dictid_C4740_
using flowable grease and their conversion to the number of relubrication impulses for conventional metering nipple sizes are given in the table ➤ Table 3. The data are valid for EP additives, for a lithium soap flowable grease with a mineral oil base ISO VG 100 to ISO VG 220 or NLGI 00 or NLGI 000.

 
   
Table 3
Relubrication quantities for stud type track rollers
 

Series1)
Outside diameter
Central lubrication adapter
Relubri­cation quantity2)
Relubrication impulses
for metering nipple of size
D
Designation
30 mm3
50 mm3
mm
g
from
up to
NUKR, NUKRE
35
40
AP8
1,1
40
24
47
52
AP10
2,4
89
53
62
90
AP14
7,3
271
163
KR, KRE
35
40
AP8
1,2
44
27
47
52
AP10
1,6
60
36
62
90
AP14
6
222
133
KRV, KRVE
35
40
AP8
0,7
26
16
47
52
AP10
1
37
22
62
90
AP14
3,2
120
72

 
 
______
 1    For stud type track rollers with hexagonal socket on both sides.
 
 
 2    Relubrication quantity and relubrication intervals for central lubrication
_dictid_C4740_
using flowable grease for the majority of applications. Note the quantity required to fill the feed lines.
 
 

Relubrication periods

Approximate definition

 

The approximate definition of the relubrication periods for single shift operation and the majority of applications is shown in ➤ Table 4 and ➤ Table 5. The data are valid for single shift operation; the relubrication quantity and relubrication intervals are valid for the majority of appli­cations. They are based on approximate calculation of the relubri­cation interval tfR. For definition of the relubrication interval
_dictid_R2970_
see chapter Relubrication    ➤ section. Within these periods, the number of relubrication impulses determined in accordance with ➤ Table 3 should be evenly distributed.

 
 

   
Table 4
Relubrication period for calculating the relubrication intervals
 

Load ratio
C0r w/Pr
Maximum operating speed
nmax in % of nD G
10
25
50
100
5 >C0r w/Pr ≧ 3
1/2 yearly
- - -
10 >C0r w/Pr ≧ 5
yearly
4 months
monthly
-
C0r w/Pr ≧ 10
yearly
8 months
2 months
14 days

 
   
Table 5
Periods in single shift operation
 

Months
Weeks
Working days
Working hours
1/2
2
10
80
1
4
20
160
2
8
40
320
4
16
80
640
6
24
120
960
8
32
160
1 280
12
48
240
1 920

 
 

Fitting of central lubrication
_dictid_C4740_
adapter

Mount the stud type track roller first

 

The stud type track roller must be mounted before fitting the adapter. The unused lubrication hole in the roller stud must be closed off using the funnel type lubrication nipple supplied. Only the lubrication nipples supplied should be used.

 

Guidelines for mounting of the adapter

 

The central lubrication
_dictid_C4740_
adapter should preferably be pressed in using a manual lever press under low, uniform pressure or carefully driven into the unused hexagonal socket of the roller stud by means of light blows with a plastic hammer; pay attention to the press-in depth l3 and the position of the hexagon ➤ Figure 25 and ➤ Table .

 

Fitting of the polyamide pipe

 

The plastic pipe must be cut off straight across and inserted into the cartridge until it stops. Only polyamide pipes to DIN 73378 should be used. Check the seating of the pipe. Note maximum pressures, maximum temperatures and minimum bending radius. The maximum pipe length up to the distributor is 1  m.

 
 

Sealing

 
 

Yoke type track rollers

Available in open or sealed designs

 

Yoke type track rollers are available in open designs and with non-contact or contact type seals ➤ Table 6.

 
   
Table 6
Seals used in yoke type track rollers
 

Yoke type track roller
Seal
STO
Open
RSTO
RNA22..-2RSR
Lip seal on both sides
NA22..-2RSR
PWTR..-2RS
Protected lip seal on both sides
continued ▼

 
   
Table 7
Seals used in yoke type track rollers
 

Yoke type track roller
Seal
NATR..-PP
Three-stage sealing on both sides plastic axial plain washers
NATV..-PP
NATR
Gap seal on both sides
NATV
NUTR
Labyrinth seal on both sides
NNTR..-2ZL
Contact washer with lamellar ring on both sides
continued ▲

 
 

Stud type track rollers

Available with seals on both sides

 

Stud type track rollers are sealed on both sides. Depending on the series, non-contact or contact type seals are used. A three-stage seal, comprising plastic axial plain washers with formed seal lips, is also used on both sides of the bearing ➤ Table 8.

 
   
Table 8
Seals used in stud type track rollers
 

Stud type track roller
Seal
KR
Gap seal on both sides
KR..-PP
Three-stage sealing on both sides by plastic axial plain washers
KRE..-PP
KRV..-PP
NUKR
Labyrinth seal on both sides
NUKRE
PWKR..-2RS
Protected lip seal on both sides
PWKRE..-2RS

 
 

Three-stage seal

Seal design

 

In the three-stage concept, there is a gap seal between the plastic axial plain washer and the outer ring, as well as a labyrinth seal between the formed seal lip and an undercut in the outer ring. The disc spring shape of the axial plain washer gives a preloaded contact seal as the third stage. It also provides axial sliding contact between the outer ring and contact washers, thus reducing friction and grease consumption.

 
 

Speeds

 

Speeds nD G

 

The maximum possible speed is essentially determined by the permissible operating temperature
_dictid_O940_
of the yoke and stud type track rollers. The speed thus depends on the type of bearing, the load, the lubrication conditions and the cooling conditions.

 
 

Speeds with lip seals

imageref_17757187211_All.gif   The speed of track rollers with lip seals is additionally restricted by the permissible sliding speed at the seal lip.  
 

Speed during continuous operation
_dictid_C1230_

 

The speeds nD G in the product tables are guide values. They were determined for:

 
 
  • grease lubrication
  • loads during continuous operation
    _dictid_C1230_
    of < 0,05 · C0r w
  • skewed running angles of α < 0,03° (< 0,5 mrad)
  • an ambient temperature
    _dictid_A4430_
    of +20 °C
  • outer ring temperatures of +70 °C
  • lubricated mating tracks
  • no external axial load.
 
 

The speeds must be reduced under the following conditions:

 
 
  • loads > 0,05 · C0r w
  • additional axial forces (skewed running)
  • insufficient heat dissipation.
 

Higher speeds

 

Higher speeds can be achieved with intermittent operation and oil impulse lubrication.

 
 

Noise

 
 

Schaeffler Noise Index

 

The Schaeffler Noise Index (SGI) is not yet available for this bearing type    ➤ link. The data for these bearing series will be introduced and updated in stages.

 
 

Temperature range

 
 

The operating temperature
_dictid_O940_
of the yoke and stud type track rollers is limited by:

 
 
  • the dimensional stability of the bearing rings and rolling elements
  • the cage
  • the lubricant
  • the seals.
 
 

   
Table 9
Permissible temperature ranges
 

Operating tempera­ture
Yoke and stud type track rollers
Open or with
gap seal or labyrinth seal
With
lip seals
With
plastic cages
With
three-stage seal
2RS, 2RSR
TV
PP
from
to
from
to
from
to
from
to
°C
imageref_19988082955_All.gif
   
–30
+140
–30
+120
–30
+120
–30
+100

 
imageref_17757187211_All.gif   Note the information on the operating temperature range
_dictid_O1970_
in the chapter Technical principles, Lubrication.
 
imageref_18348417035_All.gif   In the event of anticipated temperatures which lie outside the stated values, please contact Schaeffler.  
 

Cages

 
 

Yoke type track rollers

 

Yoke type track rollers without inner ring

With cage

 

Yoke type track rollers RSTO and RNA22..-2RSR have a sheet steel cage as standard. Yoke type track rollers RSTO up to D = 24 mm have a plastic cage made from polyamide PA66 (suffix TV). Series RSTO does not have axial guidance of the needle roller and cage assembly and of the outer ring. As a result, lateral guidance is required.

 
 

Yoke type track rollers with inner ring

With cage, with full comp­lement needle roller or cylindrical roller set

 

The series STO, NA22..-2RSR, NATR and NATR..-PP have a sheet steel cage as standard. Yoke type track rollers STO up to D = 24 mm have a plastic cage made from polyamide PA66 (suffix TV). The series NATV and NATV..-PP have a full complement needle roller set, while yoke type track rollers NUTR, PWTR..-2RS and NNTR..-2ZL have a full complement cylindrical roller set. Series STO does not have axial guidance of the needle roller and cage assembly and of the outer ring. As a result, lateral guidance is required.

 
 

Stud type track rollers

 

Stud type track rollers without eccentric collar

With cage, with full comp­lement needle roller or cylindrical roller set

 

Stud type track rollers KR and KR..-PP have a sheet steel cage, the design KRV..-PP has a full complement needle roller set. The series NUKR and PWKR..-2RS have a full complement cylindrical roller set.

 

Axial guidance of outer ring

 

In KR, axial guidance is provided directly by the contact flange and contact washer, while in KR..-PP and KRV..-PP this is provided by plastic axial plain washers, the contact flange and contact washer. In NUKR, the outer ring is guided axially by the rolling elements, in PWKR, axial guidance of the outer ring is provided by the central rib and rolling elements.

 
 

Stud type track rollers with eccentric collar

With cage or full comp­lement cylindrical roller set

 

Series KRE..-PP has a sheet steel cage, NUKRE and PWKRE..-2RS have a full complement cylindrical roller set.

 

Axial guidance of outer ring

 

In KRE..-PP, axial guidance is provided by the plastic axial plain washers, contact flange and contact washer. In NUKRE, the outer ring is guided axially by the rolling elements, in PWKRE, axial guidance of the outer ring is provided by the central rib and rolling elements.

 
 

Internal clearance

 
 

Radial internal clearance

Standard corresponds approximately to C2 or CN

 

The radial internal bearing clearance of yoke and stud type track rollers corresponds approximately to tolerance class C2 (Group 2) and, in the case of STO and NA22..-2RSR, to tolerance class CN (Group N). Values ➤ Table 10.

 
imageref_17757201419_All.gif   The values for radial internal clearance correspond to DIN 620-4:2004 (ISO 5753-1:2009). These are valid for bearings which are free from load and measurement forces (without elastic deformation).  
   
Table 10
Radial internal clearance for yoke and stud type track rollers
 

Nominal
bore diameter
Radial internal clearance
d
C2
(Group 2)
CN
(Group N)
C3
(Group 3)
C4
(Group 4)
mm
μm
μm
μm
μm
over
incl.
min.
max.
min.
max.
min.
max.
min.
max.
- 24
0
25
20
45
35
60
50
75
24
30
0
25
20
45
35
60
50
75
30
40
5
30
25
50
45
70
60
85
40
50
5
35
30
60
50
80
70
100
50
65
10
40
40
70
60
90
80
110
65
80
10
45
40
75
65
100
90
125
80
100
15
50
50
85
75
110
105
140
100
120
15
55
50
90
85
125
125
165
120
140
15
60
60
105
100
145
145
190

 
 

Dimensions, tolerances

 
 

Tolerances

imageref_17757201419_All.gif   The dimensional and running tolerances correspond to the tolerance class Normal in accordance with ISO 492, for KR, KRE and KRV to ISO 7063.  
 

The following deviations from ISO 492 apply:

 
 
  • the diameter deviations of the profiled outside surface 0/–0,05  mm
  • for NNTR, the diameter tolerance class h10
  • for NATR, NATV, NUTR, PWTR..-2RS, the tolerance class h12 for width B
  • for NATR, NATV, the roundness of the inner ring
  • for stud type track rollers, the tolerance class of the shank diameter h7 and the eccentric collar diameter h9.
 

Tolerances for Corrotect-coated bearings

 

For PWTR..-2RS-RR and PWKR..-2RS-RR , the tolerances are increased by the thickness of the Corrotect special coating.

 
 

Enveloping circle

Yoke type track rollers without inner ring

 

For yoke type track rollers without an inner ring, RSTO and RNA22..-2RSR, the needle enveloping circle Fw is in the tolerance class F6. The enveloping circle is the inner inscribed circle of the needle rollers in clearance-free contact with the adjacent construction.

 
 

Suffixes

 
 

For a description of the suffixes used in this chapter ➤ Table 11 and medias interchange http://www.schaeffler.de/std/1D52.

 
   
Table 11
Suffixes and corresponding descriptions
 

Suffix
Description of suffix
PP
Plastic axial plain washer with formed seal lip on both sides of the bearing, giving a three-stage seal
Standard
RR
Protected against corrosion by Corrotect special coating
in the case of PWTR..-2RS and PWKR(E)..-2RS
SK
Hexagonal socket only on the flange-side end face,
no relubrication facility
TV
Plastic cage
XL
X-life design
2RS
Protected lip seal on both sides
2RSR
Radial contact lip seal on both sides
2ZL
Contact washer with lamellar ring on both sides

 
 

Structure of bearing designation

 

Examples of composition of bearing designation

 

The designation of bearings follows a set model. Examples ➤ Figure 26 to ➤ Figure 29.

 
   

Figure 26
Yoke type track roller, single row, without inner ring, without seal, without axial guidance, open design, plastic cage, R = 500: designation structure


 

imageref_23118946571_en.gif

 
   

Figure 27
Yoke type track roller, double row, with inner ring, sealed, with axial guidance, optimised INA profile: designation structure


 

imageref_23118949131_en.gif

 
   

Figure 28
Stud type needle roller bearing track roller, full complement needle roller set, with axial guidance, three-stage seal, optimised INA profile: designation structure


 

imageref_23118964491_en.gif

 
   

Figure 29
Stud type cylindrical roller bearing track roller, full complement cylindrical roller set, with axial guidance, X-life design, optimised INA profile: designation structure


 

imageref_23118967051_en.gif

 
 

Dimensioning

 
 

The methods for calculating the rating life are:

 
 
  • the basic rating life to DIN ISO 281
  • the adjusted basic rating life to DIN ISO 281
  • the expanded calculation of the adjusted reference rating life to DIN ISO 281-4.
 
 

These methods are described in the chapter Load carrying capacity and life. For yoke and stud type track rollers, use the following values (values ➤ dimension table):

 
 
  • for Cr, the effective basic dynamic load rating Cr w
  • for C0r, the effective basic static load rating C0r w
  • for Cur, the effective fatigue limit load Cur w.
 

Other rating life equations

 

Other equations for calculating the rating life ➤ Equation 1, ➤ Equation 2 and ➤ Equation 3.

 

Equation 1
Basic rating life
 
imageref_13999520395_All.gif


Equation 2
Basic rating life in oscillating operation
 
imageref_13999522315_All.gif


Equation 3
Basic rating life
 
imageref_13999524235_All.gif

Legend

 
Ls
105 m
Basic rating life in 105 m
Lh
 h
Basic rating life in operating hours
Cr w
 N
Effective basic dynamic load rating. Cr w is that load of constant magnitude and direction which a sufficiently large group of apparently identical track rollers can endure for a basic rating life of one million revolutions
Pr
 N
Equivalent dynamic bearing load (radial load)
p
Life exponent:
p = 3 for yoke or stud type track rollers based on balls
p = 10/3 for yoke and stud type track rollers based on needle or cylindrical rollers
n
 min–1
Operating speed
D
 mm
Outside diameter of track roller
H
 m
Single stroke length for oscillating motion
nosc
 min–1
Number of return strokes per minute
Medias/00015D3C_mei_in_0k_0k.gif
 m/min
Mean travel velocity.
 
 

Operating life

Life actually achieved

 

The operating life is defined as the life actually achieved by a yoke type track roller, stud type track roller or ball bearing track roller. This can deviate significantly from the calculated basic rating life.

 
 

Possible causes of a deviation between the basic rating life and the operating life are wear or fatigue as a result of:

 
 
  • deviations in the operating data
  • misalignment between the track roller and mating track
  • insufficient or excessive operating clearance
  • contamination of the track roller
  • inadequate lubrication
  • excessive operating temperature
  • oscillating bearing motion with very small swivel angles, leading to false brinelling
  • wear between the outer ring outside surface and mating track
  • high vibration and false brinelling
  • very high shock loads, static overloading
  • prior damage during mounting.
 
imageref_17757187211_All.gif   Due to the variety of mounting and operating conditions, the operating life cannot be precisely calculated in advance. The most reliable way of arriving at a close estimate is by comparison with similar applications.  
 

Static load safety factor

S0 = C0r w/F0r

 

In addition to the basic rating life L, it is also always necessary to check the static load safety factor S0 ➤ Equation 4.

 

Equation 4
Static load safety factor
 
imageref_13999363979_All.gif

Legend

 
S0
Static load safety factor
C0r w
 N
Effective radial basic static load rating in accordance with product table
F0r
 N
Maximum static radial load on track roller.
 
imageref_17757187211_All.gif   Track rollers are regarded as heavily loaded at a static load safety factor of S0 < 8. Static load safety factors of S0 < 1 cause plastic deformation
_dictid_P3260_
of the rolling elements and the raceways, which can impair smooth running. This is only permissible for bearings with small rotary motions or in secondary applications.
 
imageref_18348417035_All.gif   If an application has a static load safety factor of S0 < 2, please consult Schaeffler.  
 

Frictional torque

Calculation only possible in approximate terms

 

The frictional torque MR of a yoke type, stud type or ball bearing track roller depends on many influencing factors such as load, speed and type, as well as the lubrication conditions and seal friction. Due to the wide range of these influencing factors, the frictional torque can only be calculated approximately.

 
  For designs without contact seals, the frictional torque can be calculated under normal operating conditions and moderate speed range in accordance with ➤ Equation.

Equation 5
Frictional torque
 
imageref_13999347595_All.gif

Legend

 
MR
 Nmm
Frictional torque of track roller
f
Coefficient of friction ➤ Table 12 and ➤ Table 13
Fr
 N
Radial load
dM
 mm
Mean bearing diameter of track roller (d + D)/2.
 
 

   
Table 12
Coefficient of friction for yoke and stud type track rollers
 

Type
Coefficient of friction
f
Cylindrical roller bearing, full complement
0,002
to 0,003
Needle roller bearing, with cage
0,003
to 0,004
Needle roller bearing, full complement
0,005
to 0,007

 
   
Table 13
Coefficient of friction for track rollers
 

Type
Coefficient of friction
f
Ball bearing, single row
0,0015
to 0,002
Ball bearing, double row
0,002
to 0,003

 

Validity of coefficients of friction

 

The stated factors f are valid for yoke type, stud type and ball bearing track rollers, which are unsealed or have a contact seal and are subjected to radial load. If sealed designs are used, higher coefficients of friction must be expected.

 

Influence of additional axial forces

 

Additional axial forces, such as those occurring under large skewed running angles, can lead to a substantial increase in the values, especially in the case of track rollers based on needle rollers. Track rollers based on ball bearings can support axial loads without a significant change in friction.

 
 

Displacement resistance

 

When an outer ring rolls on a track, it must overcome not only the friction within the bearing but also the rolling friction between the outer ring and the mating track. The displacement resistance is determined from the rolling friction and the frictional torque MR in accordance with ➤ Equation 6.

 

Equation 6
Displacement resistance
 
imageref_13999257867_All.gif

Legend

 
Fv
 N
Displacement resistance
fR
 mm
Coefficient of rolling friction for tracks made from hardened steel:
fR = 0,05 mm
Fr
 N
Radial load
MR
 Nmm
Frictional torque
D
 mm
Outside diameter of track roller.
 
 

Minimum load

 

Minimum load C0r w/Fr < 60

 

In order to ensure that the outer ring is driven, that no slippage occurs and that the track roller does not lift from the mating track, the track roller must be subjected to a minimum load in dynamic operation. In general, the minimum load is calculated using the ratio C0r w/Fr < 60.

 
 

Design of bearing arrangements

 
 

Adjacent construction for yoke type track rollers

Yoke type track rollers without inner ring, raceway design

 

For yoke type track rollers without an inner ring, the rolling element raceway on the shaft or stud must be hardened and ground ➤ Table 14. The surface hardness must be 670 HV to 840 HV, the hardening depths CHD or SHD must be sufficiently large.

 
   
Table 14
Tolerances and surface design
 

Diameter tolerance of shafts or studs
Roughness
Roundness tolerance
Parallelism tolerance
Without inner ring
With inner ring
max.
max.
k5 Ⓔ
g6 Ⓔ
(with point load)
Ramax 0,4 (Rzmax 2)
25% of diameter tolerance
50% of diameter tolerance

 
 

Location of yoke type track rollers without axial guidance

imageref_17757187211_All.gif   For yoke type track rollers without axial guidance, the outer ring and needle roller and cage assembly must be laterally guided ➤ Figure 30. The contact surfaces for the outer rings must be precision machined, wear‑resistant and lubricated (Ramax 2 recommended).  

Bearing parts must not be interchanged with parts from other bearings during fitting

 

Yoke type track rollers without axial guidance are not self-retaining. The outer ring and the needle roller and cage assembly are matched to each other and must not be interchanged during mounting with components from other bearings of the same size. The inner rings are matched to the enveloping circle tolerance class F6 and can be interchanged within their accuracy class (used in different combinations).

 
   

Figure 30
Lateral guidance of outer ring and needle roller and cage assembly

Symbole/00016410_mei_in_0k_0k.gif  RSTO

 

imageref_23159116811_All.gif

 
 

Location of yoke type track rollers with axial guidance

Observe dimension d2

 

Yoke type track rollers with axial guidance must be axially clamped in place. The thrust washers must be axially supported if axial loads occur. The dimension d2 in the product tables must be observed ➤ Figure 31.

 

Location by snap ring

 

Yoke type track rollers NATR and NATV can be located using conventional fasteners such as snap rings ➤ Figure 31.

 
   

Figure 31
Location by snap ring

d2 = abutment diameter
Symbole/00016410_mei_in_0k_0k.gif  NATR
Symbole/00016411_mei_in_0k_0k.gif  Snap ring

 

imageref_22471241739_All.gif

 

Firmly locate inner ring and thrust rings axially

 

For yoke type track rollers NNTR..-2ZL, NUTR and PWTR..-2RS, the inner ring and thrust rings must be located axially ➤ Figure 32.

 
   

Figure 32
Clamping of inner ring and thrust rings

Symbole/00016410_mei_in_0k_0k.gif  PWTR..-2RS

 

imageref_23159134987_All.gif

 
 

Adjacent construction for stud type track rollers

Bore tolerance H7

 

The bore tolerance H7 produces a clearance fit since the stud tolerance is h7 for studs without eccentric collar and h9 for studs with eccentric collar.

 

Design of locating surfaces

 

The locating surfaces for stud type track rollers must be flat, perpendicular and of sufficient height. The strength of the nut locating surface must be sufficiently high. The dimension must not be less than the dimension d2 in the product tables.

 

Lead chamfer

 

The lead chamfer on the locating bore must not be more than 0,5×45°.

 
 

Axial location

Axial location

 

Stud type track rollers must be axially secured using a hexagon nut. The nuts of grade 8 to ISO 4032 (M6, M8), ISO 8673, are not included in the delivery and must be ordered separately.

 
 

If heavy vibration occurs, the stud type track rollers can be located using self-locking nuts in accordance with DIN 985 or special locking washers.

 
imageref_17757187211_All.gif   For self-locking nuts, a higher tightening torque must be observed; the advice given by the nut manufacturer must be followed.  
 

Position of lubrication hole

Ensure that the lubrication hole is positioned correctly

 

The position of the radial lubrication hole is indicated on the flanged side of the roller stud ➤ Figure 33. This must not be positioned in the loaded zone.

 
   

Figure 33
Position of lubrication hole

Symbole/00016410_mei_in_0k_0k.gif  NUKR
Symbole/00016411_mei_in_0k_0k.gif  Marking (position of radial lubrication hole)

 

imageref_22456393099_All.gif

 
 

Design of mating track

Take account of Hertzian pressure

 

In the design of the mating track (material and strength, heat treatment, surface), the Hertzian pressure pH must be taken into consideration. This is dependent on the load, the contact geometry (point contact or line contact) and the modulus of elasticity of the materials.

 

Nomogram for determining the Hertzian pressure

 

The Hertzian pressure can be read from the nomogram and calculated ➤ Figure 35. The nomogram is valid for mating tracks made from steel. For other materials, the correction factor k must be taken into consideration ➤ Table 16.

 
 

Other conditions:

 
 
  • point contact
  • radius of curvature R = 500. For radii R > 500 and the optimised INA profile, correction values must be calculated ➤ Equation 10
  • mating track flat in the direction of the track roller axis
  • signs according to ➤ Figure 34.
 
   

Figure 34
Raceway radii and signs

D =  outside diameter of track roller
rL =  raceway radius

 

imageref_22456395275_All.gif

 
 

Example

 
  • stud type track roller NUKR35 with optimised INA profile
  • D = 35 mm
  • outer ring width C = 18 mm
  • radial load Fr = 2 500 N
  • cam plate, radius rL = 80 mm.
 
 

Curvature sum

Calculating the curvature sum

 

The curvature sum is calculated from the raceway radius rL and the diameter D of the track roller ➤ Equation 7.

 

Equation 7
Curvature sum
 
imageref_9007199332478347_All.gif

 
 

Calculating the curvature sum

 

pH500
= 1 250 N/mm2

 

Equation 8
Hertzian pressure
 
imageref_13998910731_en.gif

 
 

Calculating the curvature sum

 

 
=
1 250 N/mm2 · 0,85
=
1 063 N/mm2
(1 025 N/mm2 from calculation program
_dictid_C860_
BEARINX), kpH➤ Table 15.

 

Figure 35
Nomogram for determining Hertzian pressure, calculation example (purple)


 

imageref_22456397451_All.gif

 
  For an outer ring with the optimised INA profile, the following calculation provides sufficiently precise values➤ Equation and ➤ Table.

Equation 9
Optimised INA profile
 
imageref_9007199995416459_en.gif

   
Table 15
Pressure factor kpH
 

Outer ring width
Pressure factor
C
kpH
mm
10 ≦ C ≦ 15
1
15 < C ≦ 20
0,85
20 < C ≦ 30
0,83
30 < C ≦ 35
0,8

 
 

Radius of curvature R > 500 mm

  If the outer ring has a radius of curvature of R > 500 mm,➤ Equation.

Equation 10
R > 500 mm
 
imageref_13997347595_All.gif

 

Materials for mating track

High load on the mating track

 

The mating track is subjected to high load during overrolling. This produces high Hertzian contact pressures. The strength and surface hardness of the material must be matched to this load.

 

Correction factors

 

For raceways subjected to high loads, through hardened steels, case hardened steels and steels for flame or induction hardening are rec­ommended. For raceways subjected to low loads, construction steels and cast steel or cast iron materials can be used ➤ Equation 11 ➤ Table 16.

 

Equation 11
Correction for mating track material
 
imageref_9007199332491403_en.gif

   
Table 16
Correction factor k
 

Material
Material no.
Correction factor for mating track with
k
for point contact
for line contact
EN-GJL-200
0.6020
0,74
0,8
EN-GJL-300
0.6030
0,81
0,85
GG-40
- 0,85
0,88
EN-GJS-400-15
0.7040
0,92
0,94
EN-GJS-600-3
0.7060
0,94
0,96
EN-GJS-800-2
0.7080
0,96
0,97

 
 

Guide values for permissible Hertzian pressure

Selection by material

 

The table ➤ Table 17 gives a selection of materials with the associated values. The values were determined on steel test specimens; load cycles of 10 7 were achieved.

 
 

On a similar basis to the calculation of the load carrying capacity of rolling bearings, this gives:

 
 
  • pH stat for predominantly static load
  • pH dyn for predominantly dynamic load.
 
   
Table 17
Materials and guide values for permissible Hertzian pressure (selection)
 

Material
Material designation
Material no.
Hertzian pressure
Proof stress of material
New
Old
pH stat
pH dyn
Rp0,2
N/mm2
N/mm2
N/mm2
Flake graphite cast iron
EN-GJL-150
GG-15
EN-JL1020
0.6015
850
340
120
EN-GJL-200
GG-20
EN-JL1030
0.6020
1 050
420
150
EN-GJL-250
GG-25
EN-JL1040
0.6025
1 200
480
190
EN-GJL-300
GG-30
EN-JL1050
0.6030
1 350
540
220
EN-GJL-350
GG-35
EN-JL1060
0.6035
1 450
580
250
GG-40
- 1 500
600
280
Spheroidal graphite cast iron
EN-GJS-400-15
GGG-40
EN-JS1030
0.7040
1 000
490
250
EN-GJS-500-7
GGG-50
EN-JS1050
0.7050
1 150
560
320
EN-GJS-600-3
GGG-60
EN-JS1060
0.7060
1 400
680
380
EN-GJS-700-2
GGG-70
EN-JS1070
0.7070
1 550
750
440
EN-GJS-800-2
GGG-80
EN-JS1080
0.7080
1 650
800
500
Cast steel
GE200
GS-38
1.0420
780
380
200
GE240
GS-45
1.0446
920
450
230
GS-52
1.0552
1 050
510
260
GE300
GS-60
1.0558
1 250
600
300
GS-62
- 1 300
630
350
GS-70
- 1 450
700
420
Material
Material designation
Material no.
Hertzian pressure
Proof stress of material
New
Old:
pH stat
pH dyn
Rp0,2
N/mm2
N/mm2
N/mm2
Construction steel
S235JR
St 37-2
1.0037
690
340
235
S275JR
St 44-2
1.0044
860
420
275
S355J2G3+N
St 52-3
1.0570
980
480
355
Quenched and tempered steel
C45 V
1.0503
1 400
670
500
Cf53 V
1.1213
1 450
710
520
Cf56 V
- 1 550
760
550
C60 V
1.0601
1 600
780
580
46Cr2 V
1.7006
1 750
850
650
42CrMo4 V
1.7225
2 000
980
900
50CrV4 V
1.8159
2 000
980
900
Hardened and low temperature tempered steel
100Cr6 H
1.3505
4 000
1 500
1 900
16MnCr51)
1.7131
4 000
1 500
7703)
Cf532)
1.1213
4 000
1 500
7303)
Cf562)
- 4 000
1 500
7603)

 
 
______
 1    Case hardened.
 
 
 2    Induction surface layer hardening.
 
 
 3    Proof stress of the core.
 
 

Hardenable materials

 

The following materials with a purity level corresponding to that of alloyed construction steels may be used:

 
 
  • through hardening steels to ISO 683-17, such as 100Cr6. In special cases, surface hardening is possible.
  • case hardening steels to ISO 683-17, such as 17MnCr5, or in accordance with EN 10084, such as 16MnCr5. Both the hardenability and the core strength must be taken into consideration. For case hardening, a fine grained hardening structure and a case hardening depth CHD in accordance with ➤ Equation 12 is necessary.
  • steels for flame or induction hardening to ISO 683-17, such as C56E2, or to DIN 17212, such as Cf53. For flame or induction hardening, only the parts of the machine component used as raceways must be hardened. The material should be quenched and tempered before hardening. The surface hardening depth SHD is determined in accordance with ➤ Equation 13.
 
 

Heat treatment of the mating track

 

The following apply for hardened mating tracks:

 
 
  • a surface hardness of 670 HV to 840 HV
  • CHD and SHD according to ➤ Equation 12 and ➤ Equation 13 – in accordance with DIN 50190, the depth of the hardened surface zone at which there is still a hardness of 550 HV
  • hardness curves according to ➤ Figure 36 and ➤ Figure 37
  • a hardening depth of ≧ 0,3 mm.
 
 

The equations are based on the hardness curves normally achieved with skilled heat treatment.

 
 

Case hardening


Equation 12
Case hardening depth
 
imageref_13997351435_All.gif

 

Flame and induction hardening


Equation 13
Surface hardening depth
 
imageref_13997349515_All.gif

Legend

 
pH
N/mm2
Max. Hertzian pressure
CHD
 mm
Case hardening depth
SHD
 mm
Surface hardening depth
D
 mm
Outside diameter of track roller
Rp0,2
N/mm2
Proof stress of mating track material ➤ Table 17
rL
 mm
Radius of mating track – the raceway must be flat in the direction of the yoke type track roller axis ➤ Figure 34.
 
   

Figure 36
Case hardening depth CHD, hardness curve

CHD =  case hardening depth with hardness 550 HV
HV = hardness
z = distance from surface
Symbole/00016410_mei_in_0k_0k.gif  Required hardness
Symbole/00016411_mei_in_0k_0k.gif  Case hardening

 

imageref_22456399627_All.gif

 
   

Figure 37
Surface hardening depth SHD, hardness curve

SHD =  surface hardening depth
HV = hardness
z = distance from surface
Symbole/00016410_mei_in_0k_0k.gif  Required hardness
Symbole/00016411_mei_in_0k_0k.gif  Flame or induction hardening

 

imageref_22456401547_All.gif

 
 

Schaeffler guideways as mating tracks

 

The Schaeffler guideways are ready-to-fit units from the Schaeffler linear range. They are to the appropriate grade Q20 for yoke and stud type track rollers and correspond to the dimensions of standard profiles:

 
 
  • parallelism 20 μm/m
  • surface quality Ramax 0,8
  • hardness 58 HRC to 62 HRC
  • angular misalignment between the raceways max. 1 mrad (1 μm/mm)
  • deviations of the guideway cross-section +0,05/+0,015
  • length tolerance of the individual guideway +1/0  mm/m.
 
 

Protection of mating track

imageref_17757187211_All.gif   The mating track must be protected against contamination. Where necessary, covers and wipers, for instance made from felt, should be placed ahead of the track roller ➤ Figure 38.  
 

   

Figure 38
Protection of mating track against contamination

Symbole/00016410_mei_in_0k_0k.gif  Covers

 

imageref_22456403979_All.gif

 
 

Mounting and dismounting

 

Mounting

 

Track rollers must be handled with care before and during assembly. Their trouble-free operation depends largely on the care taken during mounting.

 

Guidelines for mounting

 

The products must be protected against dust, contaminants and moisture. Contaminants have a detrimental influence on the running and operating life of rolling bearings.

 
 

Do not cool the bearings excessively. Moisture due to condensation can lead to corrosion in the bearings and bearing seats.

 
 

Yoke type track rollers RSTO and STO are not self-retaining. The outer ring and the needle roller and cage assembly are matched to each other and must not be interchanged during mounting with components from other bearings of the same size.

 
 

The assembly area must be kept clean and free from dust.

 
 

Check the seat of the axis for dimensional, geometrical and positional accuracy and for cleanliness.

 
 

The seating surfaces of the bearing rings must be lightly oiled or rubbed with solid lubricant.

 
 

After mounting, the bearings must be supplied with lubricant. Finally, the correct functioning of the bearing arrangement
_dictid_B2640_
must be checked.

 
 

Depending on the application, the following are suitable:

 
 
  • induction heaters; note the manufacturer’s guidance on grease and seals
  • heating cupboard; heating up to +80 °C
  • mechanical or hydraulic presses; use mounting sleeves that cover the whole circumference of the bearing ring end faces
  • hammer and mounting sleeves; blows should only be applied concentrically to the sleeve.
 
imageref_17757187211_All.gif   Mounting forces must never be directed through the rolling elements. Avoid direct blows on the bearing rings in all cases. Ensure that the seals are not damaged.  
 

Dismounting should be taken into consideration in the original design of the bearing position. If the bearing is to be reused:

 
 
  • avoid direct blows on the bearing rings
  • dismounting forces should not be applied through the rolling elements
  • carefully clean the bearings after dismounting
  • do not use a concentrated or “hard” flame.
 
 

Mounting and dismounting of yoke type track rollers

Use a mounting press

 

If the tolerances are unfavourable, the yoke type track roller should be pressed onto the shaft or stud using a mounting press ➤ Figure 39. The inner ring must be mounted such that the pressing-in force is distributed uniformly over the end face of the inner ring.

 

Lubrication hole

 

The bearings must be mounted such that the lubrication hole is positioned in the unloaded zone. For yoke type track rollers PWTR and NNTR, defined positioning of the lubrication hole is not required.

 
   

Figure 39
Mounting of yoke type track roller using a mounting press

NUTR
Symbole/00016410_mei_in_0k_0k.gif  Mounting press

 

imageref_22456431755_All.gif

 

Axial location

 

Yoke type track rollers NUTR, PWTR and NNTR must be axially clamped in place ➤ Figure 40.

 
   

Figure 40
Axial location

PWTR..-2RS
Symbole/00016410_mei_in_0k_0k.gif  Hexagon nut

 

imageref_22456433675_All.gif

 
 

Mounting and dismounting of stud type track rollers

Use a mounting press

 

Stud type track rollers should be mounted using a mounting press if possible ➤ Figure 39.

 
imageref_17757187211_All.gif   Blows on the flange of the roller stud must be avoided. The position of the lubrication hole is indicated on the flanged side of the roller stud. It must not be positioned in the loaded zone ➤ Figure 33.  
 

Drive fit lubrication nipples for stud type track rollers

Fit the lubrication nipples before mounting the bearings

 

Stud type track rollers are supplied with loose drive fit lubrication nipples that must be pressed in correctly before mounting of the bearings ➤ Figure 41. For lubrication of stud type track rollers using the central lubrication
_dictid_C4740_
adapter ➤ Figure 24.

 
imageref_17757187211_All.gif   Only the lubrication nipples supplied may be used ➤ Table 18. If lubrication is to be carried out via the locating bore, the axial lubrication holes in the stud type track roller must be closed off using the lubrication nipples before mounting ➤ Figure 41.  
   

Figure 41
Stud type track roller with drive fit lubrication nipple and dimensions for pressing mandrel

KR..-PP

 

imageref_22456436107_All.gif

 
   
Table 18
Drive fit lubrication nipples
 

Lubrication nipple
Dimensions

 
Suitable for
outside diam­eter
D
d
L
h
dS
LS
D
±0,1
mm
mm
mm
mm
mm
mm
NIPA1
6
4
6
1,51)
- - 16 and
19
NIPA1×4,5
4,7
4
4,5
1
4,5
5
22 to
32
NIPA2×7,5
7,5
6
7,5
2
7,5
6
35 to
52
NIPA3×9,5
9,5
8
9,5
3
10
9
62 to
90

 
 
______
 1    Projection of lubrication nipple, see product tables
 
 

Axial location of stud type track rollers

Secure bearings axially

 

Stud type track rollers must be axially secured using a hexagon nut. The slot or hexagonal socket on the end of the roller stud can be used to hold the bearing by means of a key while tightening the fixing nut and to adjust the eccentric collar ➤ Figure 42. If heavy vibration occurs, self-locking nuts to DIN 985 or special locking washers can be used.

 
imageref_17757187211_All.gif   The tightening torque for the fixing nuts stated in the product tables must be observed. It is only in this way that the permissible radial load can be ensured. If this cannot be adhered to, an interference fit is required. For self-locking nuts, a higher tightening torque must be observed; the advice given by the nut manufacturer must be followed.  
   

Figure 42
Securing the bearing using an Allen key

Symbole/00016410_mei_in_0k_0k.gif  Allen key

 

imageref_22456438283_All.gif

 
 

Stud type track rollers with eccentric collar

Highest point on the eccentric collar

 

The highest point on the eccentric collar is indicated on the roller stud side, which also gives the position of the radial lubrication hole.

 
 

Commissioning and relubrication

 

Stud type track rollers have a lubrication hole for relubrication:

 
 
  • on the flange side of the roller stud
  • on the thread-side end face for outside diameters from 22 mm
  • on the shank of the roller stud, for outside diameters from 30 mm with an additional lubrication groove.
 
imageref_17757187211_All.gif   Stud type track rollers with an eccentric collar cannot be relubricated via the stud. The eccentric collar covers the lubrication hole.  
  For lubrication, only grease guns with needle-point nozzles may be used that have an opening angle ≦ 60° ➤ Figure 43.  
  Before commissioning, the lubrication holes and feed pipes must be filled with grease in order to ensure protection against corrosion; lubrication can be carried out at the same time.  
  Lubrication will be more difficult if a rolling element is located over the radial lubrication hole. Relubrication should therefore be carried out with the bearing still warm from operation and rotating if safe to do so, before the bearing comes to rest if safe to do so and before extended breaks in operation.  
  The grease used for relubrication should be the same as that used for initial greasing. If this is not possible, the miscibility and compatibility of the greases must be checked. Relubrication should continue until a fresh collar of grease appears at the seal gaps. The old grease must be able to leave the bearing unhindered.  
   

Figure 43
Relubrication using a grease gun

Symbole/00016410_mei_in_0k_0k.gif  Needle-point nozzle, opening angle ≦ 60°

 

imageref_22456440203_All.gif

 
 

Schaeffler Mounting Handbook

Rolling bearings must be handled with great care

 

Rolling bearings are well-proven precision machine elements for the design of economical and reliable bearing arrangements, which offer high operational security. In order that these products can function correctly and achieve the envisaged operating life without detrimental effect, they must be handled with care.

 
imageref_21602891659_en.gif   The Schaeffler Mounting Handbook MH 1 gives comprehensive infor­mation about the correct storage, mounting, dismounting and mainten­ance of rotary rolling bearings http://www.schaeffler.de/std/1D53. It also provides information which should be observed by the designer, in relation to the mounting, dismounting and maintenance of bearings, in the original design of the bearing position. This book is available from Schaeffler on request.  
 

Legal notice regarding data freshness

 

The further development of products may also result in technical changes to catalogue products

 

Of central interest to Schaeffler is the further development and opti­misation of its products and the satisfaction of its customers. In order that you, as the customer, can keep yourself optimally informed about the progress that is being made here and with regard to the current technical status of the products, we publish any product changes which differ from the printed version in our electronic product catalogue.

 
imageref_18350433803_All.gif   We therefore reserve the right to make changes to the data and illus­trations in this catalogue. This catalogue reflects the status at the time of printing. More recent publications released by us (as printed or digital media) will automatically precede this catalogue if they involve the same subject. Therefore, please always use our electronic product catalogue to check whether more up-to-date information or modification notices exist for your desired product.  
 

Further information

 

In addition to the data in this chapter, the following chapters in Technical principles must also be observed in the design of bearing arrangements:

 
   
   
  
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