Outside Diameter (OD) Grinder Guide

As with other sectors in the metalworking industry, grinding machine technology has constantly been evolving to meet various industry demands, such as advanced materials, 24/7 operations, increasing demands for precision components, and a lack of skilled manpower for grinder operators. In response, different types of grinding methods have been developed for specialized applications, making grinding equipment more flexible, sophisticated, and even automated, where “smart” features are incorporated for remote monitoring. That being said, today we are going to specifically discuss one type of grinding machine – the outsider diameter grinder – also known as OD grinding machine.


What Is an outside diameter grinder?

An outside diameter (OD) machine is used to grind materials between the centers on an external surface. These centers are units that contain a point at which the object can rotate. Upon contact, two surfaces will move towards the opposite directions, allowing swift operation and reducing the chance of jams. Here are some facts about the outside diameter grinder:

● OD grinder can come with either CNC or manual controls. For automated or semi-automated production, an OD grinder with CNC capability is more ideal. Manual OD grinding machines on the other hand are better suited for custom cuts.

● Modern OD grinding machines, especially the single-point models, are said to be up to six times more productive than the traditional models.

● An OD grinding machine is categorized under the cylinder grinders. A plunge grinder, also another commonly heard grinding machine, is a form of OD grinders as well.

● Unlike other types of grinding machines, both the OD grinder itself and the workpiece rotate simultaneously.

● In terms of grinding operations, an OD grinding machine works similarly to turning centers.

● An OD grinding machine operates much slower than a centerless grinder, which is essentially a type of internal diameter grinder. 


How Does an Outside Diameter Grinder Work?

Many tend to have the false conception that OD grinding is all about shaping the outside diameter of a part because of its name. But the truth is, the object to be ground needs to have a central axis of rotation. In fact, the process actually occurs on the external surface of a workpiece between centers.

To elaborate why the idea of centers is so important, the “centers'' are actually fixed endpoints that hold the object at a geometrically true spot. The true center allows grinding action to be performed by moving the workpiece in a rotational direction. As the workpiece rotates around the fixed, true-center axis, the grinding wheel rotates in the same direction simultaneously with the workpiece. 

When both external surfaces make contact, they are moving in opposite directions, allowing smoother workflow while reducing jams on the wheel. With how OD grinding operates, it is typically used to grind cylindrical surfaces or the shoulders of objects. This grinding method is characterized by its ability to provide optimal precision. And of course, the biggest variable is always the diameter: smaller diameters will achieve tighter tolerance while larger diameters yield less tolerance.


Benefits of OD Grinding

Despite its precision grinding, OD grinding is actually a fairly simple process. The biggest advantage actually lies in the true center of a circular part, meaning you can make something that isn’t round into a perfectly circular object. For instance, you can easily restore an oval object into the desired roundness without any defects or the lack of concentricity. This is essentially how OD grinding prevails over centerless grinding because it can remove invalid geometry and produce a part with perfect circularity.


Common Applications of Outside Diameter Grinders

Please take note of the fact that you won’t always be able to find the true center in all objects, especially components that are too small. Otherwise, OD grinders are typically very reliable for grinding things like equipment spindles. When performed by an expert, you can expect the ground spindle to function at peak performance.  

In addition, you’d be surprised with the fact that not only can OD grinders make precision parts but they can also mass-produce them, such as fuel injection needles for diesel engines or turbocharger rotors. This is why OD grinding remains popular in industries where high-volume production of precision parts is needed, some of which include the automotive, aerospace, machine tools, precision engineering, medical devices, and energy industries. Lastly, we’ll stress again what makes OD grinding probable is dependent on whether the operator (or robotic) is able to find the true center of the part, taking the diameter size of the part into account.

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