SK vs SHF Linear Shaft Supports: What Is the Difference?

SK and SHF linear shaft supports are used to secure the ends of round linear shafts in automation equipment, sliding mechanisms, measuring devices and other linear motion systems. Both types hold the shaft through a split clamping structure, but their mounting surfaces and installation arrangements are different.

Choosing between them does not depend on which support is stronger in general. The correct choice depends mainly on the machine structure, mounting direction, available space, shaft diameter and required shaft position.

What Is an SK Linear Shaft Support?

An SK linear shaft support is a base-mounted support block for round linear shafts. Its mounting base sits on a horizontal machine surface, and bolts pass through the holes on both sides of the support.

The shaft passes horizontally through the bore above the mounting base. A split in the support body allows the clamping screw to tighten the support around the shaft.

SK supports are commonly used in systems where the shaft must be positioned above a base plate, machine frame or mounting platform. Two supports are normally installed at opposite ends of the shaft.

What Is an SHF Linear Shaft Support?

An SHF linear shaft support uses a flange-style mounting structure. Instead of standing on a base, the support is fixed against a vertical plate, side panel or machine face.

The round shaft enters the central bore of the support, while mounting bolts secure the flange to the installation surface. The split clamping section holds the shaft after its position has been adjusted.

This structure is useful when the machine does not have enough horizontal space for a base-mounted support or when the shaft must extend outward from a plate.

SK vs SHF Linear Shaft Supports

The central difference is therefore the mounting interface. SK and SHF supports can perform the same basic task of holding a round linear shaft, but they are not normally interchangeable without changing the surrounding mounting structure.

How SK and SHF Model Numbers Match Shaft Diameter

For standard SK and SHF supports, the number in the model normally corresponds to the nominal shaft diameter in millimetres.

• SK8 is used with an 8 mm linear shaft.
• SK12 is used with a 12 mm linear shaft.
• SK16 is used with a 16 mm linear shaft.
• SHF12 is used with a 12 mm linear shaft.
• SHF16 is used with a 16 mm linear shaft.

The nominal size must match the shaft diameter, but the model number alone is not enough to confirm interchangeability. Overall dimensions, mounting-hole spacing, support height and flange dimensions should also be checked against the drawing.

This is especially important when replacing an existing linear shaft support made by another manufacturer. Products with the same nominal bore may still have different external or mounting dimensions.

When to Choose an SK Shaft Support

An SK support is generally the more practical option when the machine has a flat base plate and the shaft needs to run parallel to that plate.

Consider an SK linear shaft support when:

• The support can be bolted directly onto a machine bed or mounting plate.
• The shaft must be positioned at a fixed height above the mounting surface.
• There is enough space for the base and mounting bolts.
• The shaft is supported at both ends in a conventional horizontal arrangement.
• Simple access to the clamping screw is required during installation or maintenance.

SK supports are frequently used with round linear shafts and closed-type linear bearings. They provide a simple end-support arrangement for short and moderate shaft spans where continuous support under the shaft is not required.

When to Choose an SHF Shaft Support

An SHF support is better suited to equipment with a vertical end plate, frame face or side panel available for mounting.

Consider an SHF linear shaft support when:

• The shaft must extend from an end plate or vertical machine surface.
• There is insufficient room for a base-mounted SK support.
• The machine frame is designed for flange mounting.
• The support must fit close to the end of the shaft assembly.
• The required shaft position can be controlled by machining the mounting plate accurately.

SHF supports can simplify compact machine layouts, but the mounting face must be rigid, flat and correctly positioned. Misalignment between the supports can cause the shaft to sit at an angle or create binding in the linear bearings.

Installation Points for Linear Shaft Support Blocks

Match the support bore to the shaft

Confirm that the support model matches the nominal shaft diameter. Do not force an oversized shaft into the support or depend on excessive tightening to hold an undersized shaft.

Align both supports before final tightening

Install both end supports loosely first. Insert the shaft, adjust the support positions and check alignment before tightening the mounting bolts and clamping screws.

Keep twin shafts parallel

When two linear shafts are used together, the distance between them must remain consistent over the full travel. Incorrect parallelism can make the linear bearing blocks tight, noisy or difficult to move.

Do not overtighten the clamp

The clamping screw should hold the shaft securely without damaging the support or making unnecessary deformation. Tighten it evenly after the shaft position has been confirmed.

Check shaft deflection

SK and SHF blocks support the shaft ends, but they do not continuously support the middle of the shaft. A long shaft or a shaft carrying a relatively high radial load may deflect between the supports.

If deflection affects movement stability, a larger shaft diameter, shorter unsupported span or fully supported shaft system may be required. More information is available in our article about linear shaft deflection and support.

Information to Confirm Before Ordering

To select the correct end support blocks for linear shafts, confirm the following information:

• Required support type: SK or SHF
• Linear shaft diameter
• Quantity of support blocks
• Mounting direction and available installation space
• Mounting-hole spacing and other critical dimensions
• Linear shaft length and unsupported span
• Number and type of matching linear bearings
• Application load and installation orientation

If the support is intended to replace an existing component, provide the complete model, dimensional drawing or clear photographs with measured mounting dimensions. This helps avoid selecting a support with the correct bore but incorrect mounting geometry.

Conclusion

SK and SHF linear shaft supports both secure round linear shafts through a split clamping structure. The main difference is how they connect to the machine.

Choose an SK support when the shaft needs to run above and parallel to a base plate. Choose an SHF support when the shaft needs to extend from a machine face, end plate or vertical panel. In both cases, the support bore must match the shaft diameter, and accurate alignment is necessary for smooth linear bearing movement.

For a complete shaft assembly, the support type should be selected together with the linear shaft diameter, bearing model, shaft span, load and machine mounting structure.

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