An Oldham coupling connects two parallel shafts that are spaced apart by using two flanges with perpendicular slots keyed to each shaft. A circular disc with two perpendicular rectangular projections is placed between the flanges so that the projections fit into the slots, allowing for torque transmission while accommodating axial and radial misalignment between the shafts. Oldham couplings and flexible couplings both transmit torque smoothly while permitting some axial, radial, or angular misalignment between connected shafts.

1. Universal coupling

2. Oldham coupling
It is used to connect two parallel shafts whose axes are
at a small distance apart.
Two flanges each having a rectangular slot are keyed
one on each shaft.
The two flanges are positioned such that the slot in one
shaft is at right angles to the slot in other shaft.
To make the coupling a circular disc with two
rectangular projections on either side and at right angles
to each other is placed between the two flanges

3. Oldham coupling

4. Oldham coupling

5. Flexible Couplings
Transmit torque smoothly
Permit axial, radial and angular misalignment

6. Flexible Couplings

7. Flexible Coupling

8. Universal Joints

9. Flexible Couplings