Linear Ball Bearing Rail

The SF linear ball bearing sliding linear rail is from our mono-race ball-cage series.  These two profile sizes combine to represent a very simple yet effective linear rail solution. The SF28 and SF43 range from an extremely high load and high moment bearing system range yet is seen as a very economical solution to load movement within a compact working space envelope.  Both sizes (28mm & 43mm) of linear rail CAD data can be downloaded from here.

Typical market sectors for which these rails are used in:

  • Defence & Military: ECU Module mobilisation for cooling; Armoured vehicles; Seating (Personnel Transportation); Battery/Power Units
  • Medical: Patient Mobility; Movement of sensory devices;
  • Manual handling: Furnace Loading Equipment; Work Platforms; Extension Platforms; Cargo Movement;
  • Automotive/Coach Building PSV/Niche Vehicle: Slide out step platforms; Battery Carriers; Maintenance Aids; Automotive and racing sliding pedal box assemblies;
  • Fire & Rescue (Emergency Vehicles): Slideout Equipment Trays; Slide out Pump & Power Generation Modules;
  • Marine: Pump Access Solutions; Oil Boring and drilling platforms; Exploratory Craft; Ship Door Systems; Sail Bearings; Sliding Cockpit Covers.
  • Rail: Sliding Seating Adjustment; Battery Carrier Modules; Sliding Door Systems; Electronic Panel slides; Galley Accessibility Slides; Toilet Module Door Slides;
  • Machine Builders & Guarding: Enclosure Door Sliding systems; Sliding Gate Guards;
  • Automation, Materials handling, logistics & Robotics: Sliding Tray Extraction; Pick and Place racking solutions; Automated Drawer Slides;
  • Agriculture: Automated Feeding Systems; Silo Automation
  • Disability Access Products: Sliding Bathing Platforms; Stairlift Slides; Movement Aids; Specialist Vehicle Ramps; Vehicle Accessibility Platforms; Orthopaedic Beds;
  • Retail: Shop Counters; Display Cabinets; Sliding Drawers for Product Merchandising; Cash Till & Cash Register Drawers;
  • Electronics Industry: Racking Slides; Server Room Sliding Doors; Electronic/ Electrical Panel sliding Rails.

How SF linear ball bearing are manufactured

The SF linear ball bearing is manufactured and constructed by one or more linear motion sliders moving in a ball-cage (filled with ball bearings) inside a longer sliding rail profile.  The linear ball bearings themselves are core hardened 100Cr6 steel as standard or in cases whereby a corrosion resistant linear slide requirement is necessary for the linear ball bearing rail a core hardened AISI440C ball bearing is utilised.  This same base material elemental combination is carried over from the components that come together to make up the SR series telescopic slide rails and share the same excellent load bearing and wear characteristics.  You can find more material specifications for the linear ball bearings on page 77 of our technical download.

The linear ball bearing rails themselves are unique and stand out in the linear rail and linear motion industry due to the nature of their composition.  Both the inner and outer beam of the SF linear ball bearing sliders are made from a cold drawn nitride-hardened steel.  This steel, in turn, is processed firstly by a highly sophisticated and refined nitride hardening process.  This is a process uniquely applicable to linear rails and linear ball bearing applications that we have actually been granted an international patent for.  Its primary function of the linear rail is its ability to increase the hardness on the surface and also in the depth enough to guarantee to support the typical Hertz’s stress in the point of contacts with the rollers and the balls in heavy duty industrial linear rail sliding systems.

An important factor in being able to successfully incorporate this process in the hardened linear rail and sliding rail markets is the ability to intricately design complex geometries of the linear ball bearing rail so that core strength is retained while optimising surface hardness characteristics.  Most recently this has led to our range of ‘G’ version linear rails being optimised. 

A typical composition for our linear ball bearing hardening is a top outer layer of Magnetite Fe3 O4:850 HV at 5 microns deep.  An intermediate layer termed e-sheet hardness 750-800 HV and a thickness of 15-20 micron then follows.  A final Diffusion layer of hardness 750-300 HV that is approximately 0.05-0.70 mm in cross section follows as the third and final layer.

The linear rail inner and outer profiles are both then subjected to a black thermochemical impregnation and oxidisation process.  This, crucially in the context of linear rail performance requirements, is not a deposited, painted or coated process.  Whereby upon the use of the linear ball bearing sliding rail the contact points on a zinc plated induction hardened rail are quickly eroded and removed along with the underlying de-carbonised layer. 

The finished result

The results of this are the linear bearing rail losing its factory set pre-load and the clearance with excessive play becoming rapidly evident. In cases whereby flexion is an issue or for example a vehicle in motion with a sliding system is needed to maintain this constant pre-load so as to avoid vibration and chatter noise whilst running, our post drawing processing system allows our linear ball bearing rails to excel in performing far in advance of any other linear rail on the market.  As an added benefit this gives the sliding rail in excess of 120 hours as a result of the salt spray test according to UNI EN ISO 9227:2012.  It also acts on the contact points between the linear ball bearings and the sliding rails themselves as a constant source and release of lubrication in the daily linear motion of the application.

The combination of the nitride hardening and black thermochemical/oxidisation on the linear ball bearing rail we have come to refer to as the process T NOX 1.0.  Fundamentally this T NOX 1.0 application gives our high-performance linear rails a crucial advantage over induction hardened linear ball bearing rails which fail to offer complete coverage in certain zones when considering the maximum Von Mises stress in the contact points of the ball bearings loaded into the linear ball bearing rail assembly.  In actual fact, the NOX 1.0 process always provides a higher strength (almost uniformly above this line when shown plotted on a graph) compared to the Von Mises stress.

For situations and applications featuring a high degree of corrosion resistance such as marine, medical / pharmaceutical, Food production, waste water management, Aerospace and military/defence we can include a cathodic epoxy coating (e-coat) to the linear bearing rail (excluding the raceway contact points).  This provides in excess of 700 hours as a result of the salt spray test according to UNI EN ISO 9227:2012.

Typical loads per pair for the SF28 linear ball bearing rails can be 27000 Newton or 2753 kilogrammes (kg) or 6069 pounds (lbs).

Whereby typical loads per pair for the SF43 linear ball bearing rails can be 67100 Newton or 6842 kilogrammes (kg) or 15084 pounds (lbs).

SF standard

The standard series SF linear ball bearing rail is composed of a single slider part of the variable length, sliding inside the outer linear rail and ball-cage. The stroke of the sliding rail is limited by a combination of the internal linear slider length, the roller ball bearing ball cage and then the length of the outer linear rail. Many standard versions are available and we are also able to customise this linear rail to suit specific requests.  Special variant linear ball bearing rails have modified length, stroke and are open to customisation of changing the hole fixings and machining both the inner and outer linear rail slides to suit your specific application.  CAD download of standard linear ball bearing sliding rails for size SF28 can be found on this link or by contacting us direct.  CAD download of standard linear ball bearing sliding rails for size SF43 can be found on this link or by contacting us direct.

Prices from £54.63

SF with double sliders in the same ball-cage

Upon request, we are able to provide the SF linear ball bearing rail with 2 slider rails moving along the same common outer linear rail and ball bearing slider cage. This version is specifically designed and developed for sliding system applications with a longer oversize mobile part. The inner slider rails and rail versions are selected among the standard versions as a general rule.  However, many standard versions are available and we are also able to customise this linear rail to suit specific requests.  Special variant linear ball bearings may have modified length, stroke and are open to customisation of changing the hole fixings and machining both the inner and outer linear rail slides to suit your specific application and needs.  This arrangement of linear ball bearing rail is most common and can be seen when the length of the mobile starting point is important and correlates across the two sliders.  It is particularly useful when used to counter a high Mz moment within a typical overhanging load situation.

Prices from £54.63

SF with double slider in independent ball-cages

In addition and upon receiving special requests it is possible to provide a version of this linear ball bearing slider assembly with 2 sliders, each moving in its own independent ball-cage, to allow opposite movement direction, hence a 2 door sliding system. The slider and rail versions can be selected among the standard versions.  However, many standard versions are available and we have the ability to customise this linear rail to suit specific requests.  Special variant linear ball bearings may have modified length, stroke and are open to customisation of changing the hole fixings and machining both the inner and outer linear rail slides to suit your specific application and needs.  Typical applications this scenario is utilised in would be rail door carriages which allow independent movements of the two sliders in opposite directions, thus with a double leaf sliding door the opening with two panels is possible which converge on closing.

Ball-cage linear ball bearing rail SF28 Base Advanced Finish Options: SFX28, SFKB, SFKL

 Base: Cold drawn profile with high depth nitride hardening “T RACE NOX 1.0”, oxidation with micro oil impregnation. Ends are cut to size after treatment and sprayed with protective black paint. KL: As above base version, but with additional “T RACE e-coating 1.0”, black cathodic epoxy e-Coat cataphoresis painted for high corrosion resistance (tested for 700 hours in salt spray test according to UNI EN ISO 9227:2012) on the entire surface, except on the raceways, which however remain protected by the standard oxidation and raceway lubrication.

KB: As above KL version, but with ball bearings, linear ball cage and all ancillary fittings in stainless steel (INOX). The high load and high performance along with compact small profile dimensions are maintained for each linear ball bearing rail regardless of the anti-corrosion specification selected.

Part number & Sizing of Linear Bearing Rails

The product code for the SF linear rails is obtained, by first selecting the slider length (F), then based on the required sliding stroke (H) the rail length (L) is calculated according to the formula: L = F+H+W. Where W is a constant of 40mm for linear ball bearing rail series SF28 or 50mm for series SF43.

Main innovations in summary for the linear ball bearing rails of series SF:

  • Constant smooth movement of Linear Bearing Slides with technically advanced materials and processing
  • High strength cold drawn steel linear rail profile
  • Complete overall nitride hardened profiles with high resistance to wear and ‘Bruneling’ (indentation/deformation).
  • Lifetime constant preload of the linear rail system (unlike zinc plated slides). Play elimination.
  • Smooth black good aesthetic finish combined with the latest technology in surface hardened linear ball bearing rails
  • Greater increased high load capacity & heavy duty / high moment characteristics
  • Large ball diameter offering greater performance
  • Increased number of balls per ball-cage, therefore, higher dissipation of forces and load
  • Nitride hardened raceways for increased load capacity and resistance to impact damage
  • Shaped contoured ball-cage to offer a more rigid ball-cage from the reinforcing ribs
  • Improved caged end stoppers for robustness
  • Reduced ball-cage creeping problems due to greater impact resistance
  • Main corrosion resistance on all surfaces of 120 hours Salt spray and an option for 700 hours (excluding contact points)
  • T NOX 1.0 micro impregnation treatment to provide high standard corrosion resistance, which is far superior to traditional zinc plated slides
  • Uprated rail version with Stainless Steel (INOX) components plus coating available for corrosion resistance