Welcome to brain Stuff from house stuff works dot com where smart happens. Hi Am Marshall Brain with today's question, why is a table saw so quiet but a portable circular saw is so loud? A circular saw makes a lot more noise because of the type of motor it uses. The circular saw has a universal motor in it, and this type of motor is extremely noisy. Universal motors are called universal because they are happy to run off of either a C or D C electric power. Circular saws
use brush type universal motors. Vacuum cleaners, routers, and electric drills also use universal motors. These motors produce so much noise because the brushes rub on a slotted armature. In circular saws and drills, you also have gear train noise. Something like a radial arm saw or a table saw that you have in your garage uses an induction motor instead. Induction motors run only on a C power and they do not use brushes. That's the main reason why they're
so quiet. They also run slower and usually use a belt drive instead of a gear train. Manufacturers use universal motors because they are smaller and much lighter than induction motors. A three quarter horsepower induction motor might weigh twenty pounds. A three quarter horsepower universal motor might weigh two or three pounds. The weight difference is huge. A circular sty would be almost unusable if it contained an induction motor. If you have a quiet appliance, it probably has an
induction motor inside it. Ceiling fans and refrigerator compressors both use induction motors to keep them quiet in your house. It's always a good idea to where ear protection when using a loud power tools. Even the quiet radial arm SAD gets pretty noisy as soon as it starts chewing through a piece of wood. Do you have any ideas or suggestions for this podcast? If so, please send me an email at podcast at how stuff works dot com.
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