Date Published:Jun. 11. 2014

Explanation of Terminology

Explanation of Terminology

Temperature correction factor

This is a factor multiplied to the rated torque and max. torque depending on the operating temperature of Couplicon®.

In XGT2 XGL2 XGS2 XGT-C XGL-C XGS-C MJC MJS MJB MOR MOL MOS MSF, the rated torque and max. torque vary.
If ambient temperature exceeds 30°C, be sure to correct the rated torque and max. torque with correction factor shown in the following table.

Ambient temperature Temperature correction factor
-20℃~30℃ 1.00
30℃~40℃ 0.80
40℃~60℃ 0.70
60℃~120℃ 0.55

MOHS-C MOP-C MSXP-C are superior in heat resistance and the rated torque and max. torque do not vary depending on the operating temperature. Correction by temperature correction factor is not required.

Rotation Diameter

Rotation diameter refers to the larger of the coupling outer diameter (φA) or the diameter with the bolt head protruding (φA1)while rotating.
When using couplings in narrow spaces, pay attention to the rotation diameter. Refer to the table below for rotation diameter details.
The rotation diameter is calculated based on the reference dimensions.
As it fluctuates according to tolerance, build a margin into your design values.

Rotation diameter (by coupling type)

Moment of Inertia

This is a value that indicates the rotational difficulty of Coupling.
Smaller moment of inertia reduces the load torque at the time of start and stop.

Damping ratio

This is a parameter that represents the damping property of vibration amplitude.
XGT2 XGL2 XGS2 have a large damping ratio, thus enabling the servomotor gain to be raised.
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Max. rotational frequency

This is a maximum rotational frequency available for Couplicon®.
A value calculated based on peripheral speed 33 m/s is described and we have confirmed that this frequency does not damage the unit by a test. (Except for MOM MOHS MKM MWBS

Max. torque

This is a torque value that can be instantaneously transmitted by Couplicon®.

Allowable operating temperature

This is a temperature available for Couplicon®.
The allowable operating temperature for rubber/ resin-used Couplicon® is as shown in the following table.

Product Code Allowable operating temperature
XGT2(O.D. φ56 or Less)/XGL2/XGS2 -10℃~120℃
MJC/MJS/MJB -20℃~60℃
MOR/MOL/MOS -20℃~80℃
MSF -20℃~60℃

Thrust Reaction Force

This is a force generated when compressing Couplicon® in the shaft direction.
As the thrust reaction force becomes smaller, the force acting on the motor also becomes smaller.

Slip Torque

This is the load torque when the round shaft begins to slip against the coupling when mounted on a clamping type coupling at the specified screw tightening torque.
The load torque to the coupling must be below the slip torque. Slip torque changes with usage conditions. Always carry out tests under performance conditions similar to actual conditions in advance.

Static Torsional Stiffness

This is rigidity against torsion of Couplicon® and the inclination shown in the graph indicates the static torsional stiffness.
Static torsional stiffness for the entire Couplicon® including not only deflection part but also hub is described here.


There are seven types of shaft attachment methods as follows. Select a method according to your needs.

Set screw type

This is low cost and most common attachment method. However, since the screw point directly contacts the shaft, note that it may damage the shaft or make it difficult to remove the unit.

Clamping type

The bore is contracted by tightening force of the screw to clamp the shaft. Mounting and removal can be easily conducted, which does not damage the shaft.

Split type

the bore portion can be completely divided. Therefore, it can be easily mounted or removed without moving the device. In addition, the shaft is not damaged.

Semi-split type

This is an attachment method in which one side of the hubs is clamping type and the other side is split type. The device can be connected only on the split type side while keeping the clamping type side attached on the shaft.

Key type

As with set screw type, this is a general attachment method and can be applied to the transmission of relatively high torque. To prevent the movement in the shaft direction, this is used together with set screw type and clamping type.

Bushing type

Attachment method using taper wedge effect enables secure and stable attachment. This is suitable to high torque transmission and is the most appropriate for the spindle of a machine tool.

Adapter + Clamping type

This is a type made by inserting an adapter into the clamping type so as to be applied to 1/10 taper shaft of the servomotor.

Electrical insulation

This is insulation against electricity between both hubs of Couplicon®.
The electrical insulation value of Couplicon® with rubber/resin used between both hubs is as shown in the following table.

Product Code Electric resistance value
XGT2(O.D. φ56 or Less)/XGL2/XGS2 Not less than 2 MΩ
XGT2(O.D. φ68)/XGT/XGL/XGS Not less than 10 kΩ and not more than 1 MΩ
MJC/MJS/MJB Not less than 2 MΩ
MOR/MOL/MOS Not less than 2 MΩ
MOHS Not less than 2 MΩ
MOP Not less than 2 MΩ
MSXP Not less than 2 MΩ
MSF Not less than 2 MΩ

Constant velocity

This is speed unevenness for one rotation of Couplicon®.
In general, the higher the misalignment is, the lower the constant velocity becomes.
MFB MWBS are superior in constant velocity even when misalignment exists and is appropriate for detection devices such as encoder.


This is a backlash against the rotational direction of Couplicon®.
When high precision positioning is required, select a Couplicon® with zero backlash.

Eccentric reaction force

This is a force generated when making Couplicon® in eccentric condition.
As the eccentric reaction force becomes smaller, the force acting on the shaft bearing also becomes smaller.


This is a shaft center error.
There are three types of misalignment: eccentricity, argument, and end-play.
For details, please refer to Mounting and Maintenance.

Glossary Couplings