Drill diameter
The diameter of the drills that a specialized grinding machine can work with (see "Sharpening"). Usually, modern aggregates are compatible with a certain range of diameters, which, to one degree or another, corresponds to the most popular drill sizes.
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.
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.
