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Cutting load is determined by the hardness and moisture of the wood, the depth of the section being cut, the feed rate of the material and the sharpness of the blade. The motor must be able to handle the hardest cut without a noticeable drop in speed. In practice, the machine manufacturer's data, the power ratings of machines doing the same job and the current measured on the existing motor are considered together.
Factors that increase cutting load
- Depth of cut: The more material the blade engages at once, the more power is needed.
- Feed rate: When a log or panel is pushed through quickly, the chip load per tooth increases.
- Wood species: Hardwoods such as oak and beech, and knotty timber, are more demanding than softwood.
- Blade: Dull teeth and insufficient set increase friction, so the motor draws more current than it should.
Distinction by saw type
On a circular saw the blade's peripheral speed depends on motor speed and the pulley ratio, which is why 3000 rpm motors are mostly used. On a band saw the wheel diameter and band speed are decisive; machines with large wheels take longer to start. Panel saws drive the main blade and the scoring blade with separate motors. Since a change in speed also changes the blade speed, check the pulley and belt calculation and the maximum speed permitted by the blade manufacturer.
Collecting data on an existing machine
- Rated power and speed, and the pulley diameters
- The current measured while cutting the thickest and hardest material
- Whether the speed drops audibly during the cut
- Whether chip extraction is adequate; blocked chips also increase the load
Ambient conditions
Fine wood dust builds up on the fan cover and frame fins and reduces cooling; an IP55 motor is protected against dust ingress, but cleaning the outer surface is still the user's job. For application details see the circular saw machine motors page, and review suitable models in the motor list.