Mounted linear bearings combine a linear bushing with a housing that can be bolted to a carriage or machine plate. The assembly shortens design and installation work because the bearing seat, mounting holes, and shaft center height are already defined. However, the complete housing code remains essential.
A linear bearing block may be open or closed, single or twin, adjustable or fixed, and standard, flanged, or side mounted. In addition, the shaft can be end supported or continuously supported. Buyers must therefore confirm both the mounted unit and the shaft-support arrangement before ordering.
Inside the housing, a ball bushing recirculates balls along a round shaft. The housing provides an external mounting interface and controls the bearing’s orientation. Self-aligning designs can accommodate limited installation error, but they do not correct a bent shaft, major parallelism error, or an inaccurate machine base.
Closed units run around an unsupported shaft and are normally used between end supports. Open units include a lower opening that passes over a continuous support rail. Twin blocks contain two bearings in one longer housing, which increases spacing and helps resist moment load. Each structure has different dimensions and bolt patterns.
| Configuration | Main feature | Buyer confirmation |
| Closed single block | One bearing around an end-supported shaft | Center height, bolt pattern, and shaft deflection |
| Open single block | Opening clears a continuous support rail | Opening direction, rail width, and mounting clearance |
| Twin block | Two bearings in one extended housing | Housing length, moment load, and mounting-hole spacing |
| Adjustable block | Housing can reduce radial play | Adjustment range, shaft tolerance, and preload risk |
| Flanged or side mount | Mounting face changes relative to the shaft | Flange pattern, orientation, and machine interface |
| Lightweight unit | Lower-mass housing or bearing components | Rigidity, load, speed, and environment |
A shaft block is not the same as a linear bearing block. Shaft blocks clamp or support the shaft, while the mounted bearing travels along it. Therefore, an inquiry for a complete system should list the pillow blocks, shafts, shaft supports, and any support rail as separate components.
Mounted linear bearings are used in packaging machines, pick-and-place equipment, printing systems, assembly fixtures, inspection devices, laboratory equipment, guarding mechanisms, and light material handling. Their ready-to-mount housings simplify carriage construction and help establish center height. Twin units are useful when a moving plate creates moment loads.
Closed blocks generally suit shorter, end-supported shafts, while open blocks can travel along continuously supported shafts over longer spans. However, the block, shaft, and support arrangement must be selected as one system. Vertical axes need a separate brake or holding device because a linear guide is not a safety restraint. Buyers should state the load direction, stroke, speed, mounting orientation, and shaft support method.
Begin with the complete housing model rather than the bearing insert alone. Then provide the nominal shaft size, quantity, open or closed requirement, and mounting orientation. A machine drawing should show the center height, hole spacing, bearing spacing, shaft spacing, and available envelope.
Also confirm whether the supplier’s code represents a complete pillow block or only a bushing. Similar product photos often hide differences in center height and bolt spacing. Consequently, dimensional drawings should be compared before any cross-brand replacement is discussed.
Clean the mounting surfaces and verify that they are flat before positioning the blocks. Install the reference shaft first, then align the second shaft by moving the carriage through its full travel. Tighten fasteners gradually so the housing does not twist or pull the guide out of parallel.
For open units, keep the opening aligned with the support rail and confirm clearance along the entire stroke. Do not use the adjustment screw to compensate for a damaged shaft or major misalignment. After installation, check drag, noise, play, and seal contact. Record the final orientation before removing a unit for maintenance.
Thomson RoundRail pillow blocks are offered in several configurations. The examples below are complete product references, not generic bore codes.
| Complete Thomson model | Confirmed configuration | Nominal shaft size |
| SPB16 | Super Ball Bushing single pillow block, closed, non-adjustable | 1.000 in |
| SPB24OPN | Super Ball Bushing single pillow block, open, self-aligning | 1.500 in |
| TWN16 | Super Ball Bushing twin pillow block, closed, non-adjustable | 1.000 in |
SPB identifies a Super Ball Bushing pillow-block family, while TWN identifies the twin-pillow-block configuration in the example above. The OPN suffix identifies an open unit. The size code must be read within Thomson’s inch designation system, so 16 corresponds to a 1-inch shaft and 24 corresponds to a 1.5-inch shaft in these models.
Still, buyers should send the entire code. Open or closed construction, single or twin length, adjustment, sealing, corrosion resistance, and shaft class can change the ordered unit. A bearing insert with the same shaft size does not confirm the housing is interchangeable.
HSN Bearing Group supports model confirmation, sourcing, inspection, and custom supply discussions. First, buyers should provide the complete mounted-unit code, shaft size, quantity, drawings, and working conditions. HSN can then review the housing style, open or closed construction, single or twin arrangement, center height, bolt pattern, seals, load, speed, stroke, and shaft support.
For difficult or discontinued units, HSN can compare the block, bushing, shaft, and support geometry before discussing a replacement. Custom housings or shafts can be considered after technical confirmation. Before shipment, agreed checks may cover dimensions, hardness, appearance, fit, and movement. However, the same shaft size does not automatically confirm mounting compatibility.
Is a shaft block a linear bearing block?
No. A shaft block supports the shaft, while a linear bearing block travels along the shaft.
When is an open pillow block required?
Use it with a continuously supported shaft after confirming the opening and support-rail geometry.
Why choose a twin mounted bearing?
Its wider bearing spacing helps manage moment load, but dimensions and load ratings still need review.
Can matching shaft sizes prove compatibility?
No. Compare center height, bolt pattern, housing length, opening, adjustment, seals and shaft class.
For mounted linear bearing models not listed above, contact HSN for confirmation. Send the complete unit code, photos, drawings, dimensions, quantity, shaft arrangement, and working conditions.
This article is based on independent analysis of publicly available technical information and industry understanding for knowledge sharing. All brand names and trademarks mentioned belong to their respective owners. HSN Bearing Group is an independent bearing supplier and technical service provider.
Tel: +86 156 6578 7336 Email: service@hsnindustrial.com Website: www.rollingparts.com www.hsnbearings.com