FAQ Frequently asked questions

Overview

Operating principle Keys and splines Self-centering Reducing hub pressure Reduced tightening torque Stainless steel clamping sets

Operating principle

How do clamping sets, locking assemblies and shrink discs work?
The following section explains the basic operating principle of the shaft-hub connections we offer.
The fundamental principle of these connecting elements is frictional locking. Similar to a thermal shrink fit, a force is generated between shaft, hub and clamping element by forced elastic deformation of the components involved.
In a thermal shrink fit, this force is generated when the outer ring contracts during cooling.
In our shaft-hub connections, this force is generated by the forced axial displacement of matching tapered surfaces. Shrink discs and clamping sets achieve this displacement by means of their screws. With a locking assembly, the design engineer must provide an external pressure flange to generate the required axial force.
As soon as the shaft-hub connection has to transmit torque or axial force, the resulting friction force counteracts relative movement and prevents slipping.
This offers significant advantages compared with the supposedly safer positive-locking method using keys or splines:

  • No fretting or backlash under alternating or pulsating load
  • Easy disassembly
  • Simple repositioning of the hub
  • No weakening of shaft or hub by keyways
The last point in particular is often underestimated.

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Advantages of clamping sets compared with keys and splines

Are you still using keys or splined profiles to connect shafts and hubs?
Why not try our clamping sets?
The advantages are obvious:

  • No backlash under alternating direction of rotation and dynamic loading
  • No weakening of shaft and hub, as no keyway is required
  • Easy disassembly
  • Simple hub adjustment during assembly
  • Lower cost because no machining of shaft and hub is required
We will be glad to support you in changing from keyed connections to clamping sets. Please call us or send us an email.

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Self-centering vs. non-self-centering

A distinction is made between self-centering and non-self-centering clamping sets.
Self-centering clamping sets (for example W926) can center the hub on the shaft with an accuracy better than 0.05 mm and therefore provide correspondingly good concentric running. In general, additional centering of the shaft directly in the hub - for example by means of a sliding fit - is not required.
When using non-self-centering clamping sets (for example W921), a sufficiently long centering fit between shaft and hub is required instead. This centering fit should be at least twice the width of the clamping set. The advantage of non-self-centering clamping sets is usually their ability to compensate for larger fit deviations between shaft and hub.

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How can hub contact pressure be reduced?

By reducing the tightening torque of the screws (see also FAQ: reduced tightening torque). The relationship between tightening torque and contact pressure is generally close to linear. However, the tightening torque should not be reduced below 60% of the specified value. Please ask us in special cases. Back to top ↑

Is it possible to tighten the screws of clamping sets with lower torque?

Yes. In general, the tightening torque of the screws can be reduced to 60% of the value specified in the data sheet. Please ask us in special cases. In this range, the transferable force and transferable torque change approximately linearly, as does the pressure on shaft and hub.

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Which stainless steels can be used for clamping sets?

In principle, many stainless steels are suitable for the manufacture of clamping sets. We differentiate between AISI 300 and AISI 400 grades.
Our standard stainless steel clamping sets are manufactured from martensitic grades, preferably 1.4057 or similar materials.
Where higher corrosion resistance is required, for example due to cleaning agents in the food industry or possible chloride-induced corrosion, we switch to austenitic stainless steels.

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