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Attaching gears


Different methods for securing gears

There are many solutions for securing a gear to a shaft. Below are several options that may help with your application.


Secured using a
Set screw
Secured using a
Set screw

Securing using a setscrew :


Principle : Securing a gear by using a setscrew is very simple. A threaded hole should be machined into the hub of the gear. The tightening forces are concentrated on the edges of the threads of the cup headed screws (HC ranges).



Advantages : This type of fixing improves the tightness of the assembly and limits any movement.
However the value of torque that can be transmitted is limited and it is therefore this arrangement is only recommended for securing gears with a low module. The threaded hole is standard on all HPC pulleys.
Please Note:  the screws can become loose if subjected to vibration



Secured using a Key


Secured using a Circlip
Secured using a
Key and Circlip

Securing using a key


Principle : The use of a key ensures that a secure it possible to make a connection by blocking rotation. It requires the machining of a groove in both the shaft and the bore. For manufacturing reasons the groove in the bore must be made along its entire length.


A parallel key is a rectangular piece of metal that mounts partly in the shaft and partly in the bore of the hub. The machining of the groove in the shaft is normally performed with the aid of a two-bladed cutting tool.
A keyway of this type makes it possible to transmit high levels of torque.

Securing using a key->  Securing using a key


Disk (or half moon) keys are used for the transmission of lower values of torque. The machining of the keyway into the shaft is very easily done using a three bladed cutter.

A keyway does not stop axial movement of the assembly; it must therefore be combined with another locking system, such as a thread and a nut or more simply by using a circlip.


Securing using a key->  Securing using a key

Securing using a circlip


Principle : Circlips stop axial movement between two components.
There are two types of circlips, an external one for shaft mounting and an internal one for mounting inside a bore.


Use : The use of a circlip requires a groove to be cut into either the bore or the shaft. The circlip are then fitted from one end of the shaft (or bore) with the aid of a special tool.


Note:a minimum (or maximum) clearance diameter is needed for the installation.

external circlip internal circlip Securing using a circlip

The use of circlips is often used in association with a keyway in the assembly of pulleys or spur gears.

Secured using a Dowel pin
Secured using a
Dowel pin

Securing using a dowel pin


Principle : A dowel pin is used to attach two component together, to ensure accurate relative positioning of two components or for transmitting movement.

It can also play a safety role by shearing in the event of a violent shock pr overload.


Use : In normal operation, the pin is subject to shearing forces and should therefore be used in cases where there is relatively little torque involved. Its use is not recommended where frequent removal is necessary. The drilling of the mounting holes for the dowel pins is generally done after assembling the two components in order to guarantee perfect alignment.

The use of a cylindrical dowel pin requires the precise machining of a hole through the shaft and gear. When using a split dowel pin, normally a drilled hole is sufficient as the pins will deform slightly during insertion and gives a very good resistance to vibration.

This type of assembly is excellent for small pulleys or gears with low modules.

Secured using a Locking assembly
Secured using a
Locking assembly

Securing using a locking assembly


Principle : By tightening the screws, the user deforms a conical ring and creates a strong compression force between the shaft and the bore.

The lock obtained is very strong and rigid (i.e. backlash-free) but can be easily disassembled.

locking assembly  Secured using a locking assembly


Advantages : By avoiding the need to cut a keyway, this system actually increases the sectional strength of the shaft and avoids the creation of stress points and the risk of cracking due to metal fatigue. Compared to other securing methods of equal diameters, the transmissible torque with this method is much higher.


Machining required to be done to the shaft and the bore is limited to ensuring an H8/h8 tolerance and a surface finish of at least Ra=1,6mm for self-centering assemblies (Models RT25 and RTL450). A locating guide should be used with the other types of assembly.

These locking assemblies are recommended for use with all types of toothed wheels, and especially for pulleys, sprockets and gears with large pitches or high modules.

Securing using a self lubricating bush
Secured using a
Self lubricating bush

Securing using a self lubricating bush


Principle : This very simple system provides reliable, simple and efficient rotational guidance. It works on the principle of limiting friction between the shaft and bore by using two self lubricating bushes (type MET). At the same time it stops axial movement of the rotating object.


The most practical locking elements are locking rings (BAG). They do not require any special machining on the shaft and can be positioned at any point along its length thus allowing for adjustments to the position of the pivot point.

Locking ring  BAG0

Locking ring BAG1

The use of Ollite MET self-lubricating bushes requires a maximum tolerance of f7 on the shaft and H7 on the bore (see ISO 2795 and 2796)

Secured using a Locking ring
Secured using a
Locking ring

Securing using a locking ring

Securing with a locking ring is a fast and efficient method of securing all types of gears. Two solutions exist, locking with half a locking ring (type BAG2), or locking with the aid of a full collar (BAG1).


Using a half-ring BAG2) : The first solution involves the machining and removal of half of the gear hub and the drilling/tapping of two threaded holes in the remaining section of the hub.

half-ring CT
half-ring CT
Securing using a locking ring


Using a locking ring (BAG1):The second solution involves reducing the width of the hub and the machining of two channels as shown in the diagram below.

locking ring CC
locking ring CC
locking ring


In both cases, the result is a completely rigid joint which is perfectly suited to the transmission of high levels of torque.

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