Cylindricity, concentricity and surface finish are vitally important to smooth and dependable operation, and that’s what centerless and cylindrical grinding provide. These two machining processes both produce precise cylindrical shapes but they differ in several ways.

In centerless grinding, the workpiece is held on a long, thin by a regulating wheel that pushes it against the grinding wheel. So in centerless grinding the workpiece is located by its outside diameter while grinding between centers holds it on its centerline. Note that a cylindrical grinding doesn’t have to hold the workpiece between centers. It could use chuck jaws or a collet instead.

In centerless grinding the grinding wheel turns the workpiece with the regulating wheel controlling rotation speed. This provides the differential motion needed for material removal.

In cylindrical grinding the workpiece turns in the opposite direction to the wheel. This is achieved by driving workpiece rotation from a chuck that usually holds one of the centers. To make the workpiece turn, a driving “dog” is fitted to it, and this is pushed around in a circle by a pin on the chuck.

Both of these grinding processes are capable of producing very smooth surfaces. The main differences are accuracy and throughput.

Centerless grinding is capable of high throughput rates. However, the machines take time to set up. In contrast, a changeover or setup on a CNC cylindrical grinder can be accomplished in a few minutes. The downside is that part loading and unloading is slower than a centerless grinder running in through-grinding mode. Therefore, centerless is preferred for high volume machining, providing it can maintain the geometric precision needed. In general, cylindrical grinding is more accurate and achieves superior roundness. The difference is small – a matter of tenths of a thousandth of an inch – but it’s often worth paying the additional cost when function depends on precision.

Impro performs both centerless and cylindrical precision machining on modern CNC grinders. The largest parts that can be centerless ground are 2” diameter while our cylindrical grinders can handle parts up to 14” diameter. Impro experts can advise you which grinding technique will yield the best cost and quality solutions. Contact us to discuss your precision machining needs.