Motor power
Rated power of the electric motor of the machine. The more powerful the engine, the higher the speed and intensity of processing can be, the larger discs can be used with the machine and the better it is suitable for working with hard, stubborn materials. On the other hand, a powerful motor consumes a lot of energy (which may require special connection — see "Power") and significantly affects the dimensions, weight and price of the entire unit. Therefore, manufacturers choose this parameter based on the type (see "Machine") and the desired characteristics of speed, productivity, etc. In fact, this means that engine power is rather a secondary parameter, and when choosing, it makes sense to pay attention to more practical points — disk diameter, rotation / movement speed, etc.
Maximum chain sharpening angle
The presence in the design of the machine of a mechanism for changing the placement of the chain relative to the grinding disk. The sharpening angle of the saw chain largely depends on the main purpose of the tool: for transverse or longitudinal sawing. Since the resistance of wood is always noticeably higher during longitudinal sawing, the edge of the tooth must also be very sharp. Knowing the maximum value of the sharpening angle will be very useful before buying a grinder.
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 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.
