A centerless grinder is a type of OD grinder where the workpiece, rather than being supported on either end,

is held against the grinding wheel by a second smaller wheel, turning at a slower RPM and known as a regulating wheel, while resting on a workblade. These machines can be used in infeed and throughfeed mode.

Centerless grinding is much easier to combine with automatic loading procedures than centred grinding; throughfeed grinding, where the regulating wheel is held at a slight angle to the part so that there is a force feeding the part through the grinder, is particularly efficient. Plunge grinding involves feeding the part onto the support blade and then lowering the grinding wheel radially into it.

The workblade is angled slightly towards the regulating wheel, with the workpiece centerline above the centerlines of the regulating and grinding wheel; this means that high spots do not tend to generate corresponding opposite low spots, and hence the roundness of parts can be improved.

A special version of centerless grinding is shoe type centerless grinding. In this case, blade and regulating wheel are replaced by steel shoes.