Disc diameter
Regular diameter of the disk (see "Working element") used by the machine for dry processing (see above). When grinding and polishing, usually, we are talking about the maximum diameter of the disk that can be installed on the tool — a larger nozzle will either be ineffective or not fit into the dimensions of the seat at all, but a smaller diameter disk, usually, is installed without problems (of course, if the hole diameter matches — see below). For grinding machines, the diameter of the disc corresponds to the diameter of the sanding pad, which is necessary for the full use of the disc.
The larger the regular disk — the heavier and more powerful the machine, usually, the better it can cope with complex work of a large volume. At the same time, for small everyday tasks like periodically sharpening knives or chisels, a small disc is quite enough.
Bore diameter
The bore diameter of the dry cutting discs (see above) used by the machine. In order for the nozzle to be used normally with the machine, it must match it not only in diameter and thickness (see the relevant paragraphs), but also in the size of the mounting hole.
Disc thickness
The thickness of the "dry" blade (see "Dry Machining") for which the machine is designed. Usually, we are talking about the maximum thickness of the disc that can fit on the seat — most models allow the use of thinner nozzles.
Note that this parameter depends on the type of sharpening (see above): working with chains and saw blades involves a small thickness of the discs, universal sharpening is the opposite. And for grinding models, the thickness of the disc is not relevant at all, even if the disc is provided in the design; see "Machine" for details.
Disc speed
The nominal speed of rotation of the disk for dry processing (see above), provided by the machine; for models with adjustable rotation (see below), the maximum rotation speed.
For the same disc diameter and material, a higher speed provides more intensive processing, and a slower rotation contributes to accuracy and precision. In addition, optimal speeds depend on the composition of the disc and the material being processed; detailed recommendations with specific figures for a particular situation can be found in special sources.
A separate category is grinding machines with disk-shaped working elements: in such units, the actual speed of movement of the disk surface relative to the workpiece depends on how close the contact point is to the centre of the disk.
