Centerless cylindrical grinding
and centerless cylindrical grinding machines 2

How does centerless grinding work?

Centerless grinding is a machine process in which material is removed from the workpiece by machining. For this, the workpiece is positioned between two rotating wheels, supported by a workrest blade.

The regulating wheel regulates the rotational speed of the workpiece, supports it, and generates the axial feed through its inclination.
The grinding wheel is abrasive and removes the desired excess material.

The workpiece is not clamped in place. It is supported between the wheels and on the workrest blade.

Even very long and delicate workpieces can be processed.

Centerless Grinding

Centerless cylindrical grinding enables high precision combined with high productivity.

It is possible to machine a wide range of cylindrical workpieces, from a few grams to several tons in mass, within very tight tolerances.

Grinding methods

Centerless cylindrical grinding employs two fundamentally different principles.

Throughfeed grinding
is used when only the cylindrical portion of a workpiece with the largest diameter needs to be machined. The rotating workpiece moves axially along the workrest blade, between the grinding wheel and the regulating wheel, through the entire grinding gap.
The inclination of the regulating wheel relative to the workpiece axis generates the axial workpiece feed.
Infeed grinding (plunge grinding)
is used when cylindrical areas smaller than the largest diameter need to be machined (e.g., bearing seats of gear shafts or camshafts) or for more complex profiled areas.
The workrest blade, grinding wheel, and regulating wheel are fitted with a negative profile adapted to the workpiece. Loading and unloading are performed separately. The regulating wheel supports the workpiece, sets it in rotation, and moves it against an axial stop. The grinding wheel moves radially toward the workpiece and removes the desired stock removal.

Selection of grinding wheel

The grinding wheel must be selected depending on the material to be machined, the tolerances, the amount of stock removal, the grinding productivity, the desired surface finish and other parameters.

Grinding wheels differ according to:

diameter
Width
Grain size
density
bonding
hardness
Heat dissipation capacity

Height of the workpiece

The height of the workpiece relative to the grinding and regulating wheel is the basis for perfect roundness and tolerance.

The grinding and regulating wheels of the machines are usually mounted at the same height. The central axis of the workpiece runs above these axes.

This height difference is crucial for the resulting roundness. Roundness problems in centerless cylindrical grinding usually occur as polygons with an odd number of sides. Triangles, pentagons, heptagons, etc., are produced. Each height position, depending on the current diameters of the grinding wheel, regulating wheel, and workpiece, results in an improvement or worsening of the roundness for each of these polygon shapes. The height position must therefore be adjusted to minimize the polygon defects of the raw material and prevent the creation of new defects.

cooling

The coolant is crucial for the grinding result. If the coolant is supplied without pressure via a spray nozzle, it cannot break through the air cushion that forms due to the rotation of the grinding wheel. While the coolant will still remove heat and chips, it will not improve the actual cutting process. By selectively supplying the coolant via needle nozzles, grinding performance and the grinding result can be improved.

Experience

Experience, advice, training and service are crucial in centerless cylindrical grinding.