Hardened and ground shafts are used in linear motion applications where ball bushings, guides and machine structures need to move smoothly and accurately. The combination of a hard running surface and a tougher core makes these shafts suitable for applications involving point loads, shocks and bending moments. As a result, they are widely used in mechanical engineering, automation and conveyor systems.
At LM Systems, hardened steel and ground CF53 shafts are kept in stock as standard with an h6 tolerance. This tolerance is well suited to many applications involving linear bearings and ball bushings. For hollow shafts, C60 material in h7 quality is used as standard.
Standard stock of CF53 and hollow shafts
To enable short delivery times, we keep CF53 shafts in stock in diameters ranging from 4 millimetres up to and including 120 millimetres. This provides a broad range for both compact linear motion applications and heavier structures requiring larger shaft diameters.
Hollow shafts are also available in diameters ranging from 12 millimetres up to and including 60 millimetres, manufactured from C60 material in h7 quality. The choice between solid and hollow shafts depends on the application, the load, the span and the required structural configuration.
Material selection for linear shafts
CF53 is a widely used material for hardened and ground shafts. It is suitable for applications where wear resistance, dimensional stability and a reliable running surface are required. However, CF53 is not the best choice for every environment. Where corrosion resistance is important, for example in damp or humid environments, stainless steel X46 becomes an option.
For applications where both corrosion resistance and high wear resistance are required, X90 can be selected. This is a high-alloy stainless steel with excellent wear-resistant properties. The choice between CF53, X46 and X90 therefore depends on the specific application. Factors such as moisture, load, wear conditions and the requirements of the linear motion all need to be taken into account.
Why hardening depth is so important
The hardening depth determines how well a shaft can withstand the loads generated by rolling balls. During linear motion, the balls exert localised pressure on the surface of the shaft. This creates high contact stresses. The hardened outer layer prevents the balls from pressing into the running surface and causing permanent deformation.
At the same time, the core must remain sufficiently tough. It is precisely this tough core that allows the shaft to absorb shocks and bending loads without becoming brittle. The balls must therefore remain within the hardened zone, while the core continues to withstand the mechanical loads.
An additional advantage of the hard surface is that it can withstand higher contact stresses without deformation. In certain situations, this may allow a smaller shaft diameter to be used. This is only possible when deflection, load and the specific application have been properly assessed from a technical perspective.
When are supported shafts required?
With longer spans or higher loads, shaft deflection increases. In such situations, an unsupported shaft may deflect too much. This affects accuracy, bearing service life and the running characteristics of the machine.
Supported shafts may then be required to limit deflection. This is particularly relevant for longer strokes, heavy loads or applications where movement needs to remain smooth and precise. The choice to use supported shafts is therefore based on the load, stroke length, span and required rigidity.
Reliable linear motion starts with the right shaft
What load will be applied to the shaft, how large is the span and in what environment will the machine operate? For a standard application, CF53 with an h6 tolerance is often a logical choice. As soon as moisture, cleaning requirements or increased wear come into play, materials such as X46 or X90 are more commonly selected.
The hardening depth also deserves careful consideration. The outer surface must be hard enough to withstand the point loads exerted by the balls. At the same time, the core must remain tough so that the shaft can withstand shocks and bending moments. This combination largely determines how reliable the linear motion will remain in practice. Unsure about the correct shaft diameter, material selection or type of support? Contact us. Our specialists will be happy to discuss your application and help you select a hardened and ground shaft that matches the load, operating environment and required motion.