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Siemens AG
Entry type: FAQ Entry ID: 31642168, Entry date: 09/22/2008

Import info when installing transmission means

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What should be observed when installing transmission means?





Transmission means such as couplings or belt pulleys must be carefully and gently fitted onto the shaft.

The transmission means should only be used when they have been drilled and balanced.

The balancing of transmission means must correspond to the balancing of the rotor.

The balancing of the rotor is stamped into the front face of the shaft extension:


F = Full-key balancing

H = Half-key balancing


Since 01 June 1998, half-key balancing for three-phase machines has been stipulated in accordance with DIN ISO 8821.






Shaft end with balance code






If the balancing of the rotor and transmission element do not correspond this can result in unsmooth running and, in extreme cases, damage to bearings.

Caution! Machines with half-key balancing which run using a featherkey but without attached transmission element e.g. for testing purposes, are highly unbalanced.

This operation is only allowed for a short time during commissioning and only if urgently required. If the hub length is shorter than the shaft extension, the featherkey protrudes out of the hub and also results in unbalance with the risk of operating vibrations and, in extreme cases, damage to the bearings.






  • Medium lenght featherkeys

  • Offset featherkeys

  • Compensating bushing






Safety note

The featherkeys are only secured against falling out during transport. If on machines with two shaft extensions no transmission element is fitted on one shaft extension, secure these featherkeys from being slung out. Also, when using rotor counterbalance type "H" (standard version) shorten to around half the length.






Prior to fitting the transmission elements, the bore diameter and balance status are to be checked.

The shaft extension is to be cleaned thoroughly.

The default settings of the coupling manufacturer are to be observed.

The transmission means to be attached must be warmed up to around 100°C for expansion.

They must then be attached in one seamless process, either via the threaded face hole in the shaft or by pushing on by hand.

It is prohibited to strike the transmission means with a hammer or similar to seat it.



1. Shaft extension

4. Thread rod or spindle

2. Center hole with thread 5. Pressure plate
3. Transmission means to be attached  

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