Planing depth
The greatest thickness of the layer of material that the planer can remove in one pass (most often the design provides for depth adjustment). The larger this parameter, the more performant the tool will be and the better it will be suitable for large-scale work. On the other hand, in fact it is rarely necessary to remove a large amount of material at a time, and tools capable of this require powerful (and therefore expensive) motors. Therefore, in most consumer-level models, the planing depth does not exceed 2 mm; more "deeper" units, usually, belong to the professional class.
Grooving depth
The greatest depth of the groove that can be cut into the workpiece with a planer.
Grooves are narrow and long slots used, in particular, for tenoning wooden parts. Some models of electric planers are equipped with special tools that make it easier to cut grooves.
Knives
The design of knives intended for use with a planer and, usually, supplied as standard. The type of knives does not affect the performance of the tool, but in the case of dullness or nicks, the methods for correcting the situation differ significantly.
— Unilateral. As the name suggests, these knives are sharpened on one side only. If defects appear on the blade, it can be removed and sharpened or the edge straightened. Technically, such an operation can be carried out many times, but it requires not only time, but also appropriate skills and equipment.
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Bilateral. Knives sharpened on both sides are very convenient due to the fact that when the edge becomes dull or serrated, it is enough to remove the knife and install it on the other side, with a “fresh” blade. On the other hand, such blades do not allow sharpening — when the second side of the knife becomes unusable, the only option is to replace it.
In box
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Dust collector. The presence of a dust collector in the delivery set — a special bag for collecting dust, chips and other waste that occurs during operation. This bag connects directly to the waste chute, so that the waste stays in the dust bin and cleaning up after work becomes much easier. However the dimensions of the tool with the bag attached increase somewhat, and during work it is necessary to monitor its filling and release it in time — otherwise the accumulated chips can jam or even break the planer.
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Case (bag). The presence in the delivery set of a special case — a suitcase for storing and carrying a tool, which also provides some degree of protection. Using a case for such purposes is much more convenient than various "non-native" packages: it is optimally adapted to a specific planer model, in addition, it often has specialized compartments for additional accessories. There are also rag bags, lighter, but at the same time less protective.