Understanding rotary shafts, axes, and motor shafts: A guideline

Rotary shafts are an essential element of modern mechanical engineering. As a rotating component, they transfer moments and rotary motion. Rotary shafts can be manufactured from different materials, which are selected specifically to match the application. The materials include unhardened steel, stainless steel and hardened steel.

Motor shafts are a special type of rotary shafts designed to create a direct connection between a motor or other force source and the mechanical part of a machine.

Motor shafts and rotary shafts are used to transfer torque in various systems and applications. These include synchronous belt drives as well as chain drives and other applications that transfer torque directly without a gear ratio. Learn more about mechanical force transfer in rotary motion here. In many cases, shaft couplings are used as connecting elements at the ends of rotary shafts.

You can find rotary shafts and motor shafts at MISUMI webshop.

In short: Rotary shafts and rotary axes

• Rotary shafts (rotary shafts) transfer rotary motion. An example is the rotary shaft between the motor and the gearbox. They mainly absorb torsional forces.
• Motor shafts (drive shafts) are a special form of rotary shaft located in a motor. Couplings are frequently used to transfer force of the rotary motion and torsional forces to other components.
• Axes are stationary components and, unlike the shaft itself, do not rotate. They mainly absorb flexural forces.
• Linear shafts are fixed just like axes, but are used as high-precision guide shafts. They are a special shape of axis and are usually manufactured to high precision and are surface hardened.
• In physics, the axis of rotation is the theoretical axis around which a rotary component rotates. It is shown in engineering drawings as a dashed-dotted line.
• In mechanics, the axis of rotation is a fixed shaft for guiding and mounting rotationally mounted attachments.

Requirements for rotary shafts

Rotary shafts, also called torque shafts, must be able to provide sufficient torque transfer. This can be achieved by combining suitable materials and correct dimensioning.

The dimensioning of the rotary shaft depends on the torque to be transferred in relation to the length and diameter of the shaft. Too small a diameter will cause an overload, resulting in the destruction of the torque shaft. Any incident centrifugal or flexural forces must also be taken into account. The surface of the rotary shaft must have high accuracy, straightness, and a good surface finish. An uneven surface can cause vibrations or uneven operation of the torque shaft. Rotary shafts must be supported with a rolling bearing or bearing housing in order to enable low-friction rotary motion.

However, rotary shafts can not only be used as components for rotary motion, but also as stationary axes. In physics, an axis of rotation refers to the stationary line (axis) about which a fixed, rigid body rotates. In mechanical engineering, however, the axis of rotation is also understood to be a component that is installed as a rigid axis in a system and serves to guide and mount rotary attachments. On rotary shafts - in contrast to rotary axes - the entire assembly, consisting of the rotary shaft and the components attached thereto, rotates around itself.

MISUMI offers a number of possible combinations for positioning rotary shafts, which include one-sided and two-sided support of the rotary axis. These combinations permit locking the axial position to maintain the required roundness and straightness, and to avoid undesirable vibrations that can lead to inaccuracy, component loss, increased wear, and unwanted noise generation. High-precision rotary shafts allow high speeds to be achieved while maintaining the required smoothness of motion thanks to the axial position lock.

Requirements for rotary axes

If a rotary shaft is used as an axis of rotation, resistance to bending plays a major role since the rotary shaft is primarily subjected to bending moment loads. In order to transfer the forces exerted on the rotational axes and rotary axes to the axes supports, these can be manufactured using high-strength materials such as stainless steel, aluminum, or titanium.

Requirements for motor shafts

A motor shaft is a connecting link between the motor and the machine that is directly driven by the motor. They are mainly stressed by torsion-induced twisting. This is where the entire assembly consists of the motor shaft and the attached components, requiring a rolling bearing or bearing housing to mount the shaft.

Motor shafts and torsional shafts are particularly suited for mechanical engineering and plant construction because they have high torsional resistance and very high concentricity and roundness accuracies. This permits low-vibration transfer of rotary motion and torque at high speeds. In addition, the force transfer points can be post-processed by hardening for even higher torsional strength. MISUMI motor shafts are equipped with center holes on the end faces for easy mounting.