What are the types of shaft coupling to use on CNC ?

Coupling are used for transmitting torque between two shafts even when they are misaligned. For hobbyist CNCs they are used to connect the Stepper Motor axis and the leadscrew/ballscrew.

Rigid Coupling
The basic (and worst) coupling is the rigid couplings:

Rigid_Coupling

This coupling is good for transmitting torque between two shafts and has no backlash but doesn’t allow misalignment among shafts and will wear or damage the shafts very soon.

Oldham Coupling
The Oldham coupling has 3 discs (normally two metal discs and one plastic disc) and allow parallel shaft misalignment (offset) :
oldham_coupling
Oldham coupling can reduce the backlash, but there are better options as we will see next.

Jaw Coupling
As known as Spider Coupling or Lovejoy Coupling:
jaw_coupling
The Jaw coupling has 2 metal discs and an elastomer filling disc internally. They are good for torque transfer and damping support, but have some backlash.

Helical Coupling
As known as Beam coupling is a hollow cylinder with helical cut:

helical_coupling

This coupling can support some degrees of misalignment and have low backlash.

Bellows coupling

Bellows coupling is a type of cylinder cut or electro-deposited to become a bellow:

bellow_coupling

This type of coupling allow misalignment and the lowest backlash of “flexibles couplings”.

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