That's like asking why wheels are circular.
gear or gears
Yes there are. There are sliding gears inside power drills.
6
5
Yes. How do you think they run?
Software is available to design non-circular gears such as "Gearify" and "Gearotic"
Most hand-held circular saws have no gears--the blade is mounted directly on the motor shaft. The exception is the original-design Skilsaw, which uses a worm gear to drive the blade. (The company makes both styles, today).
Divide 3.14 by the diametral pitch. Worm gears are a compact, efficient means of substantially decreasing speed and increasing torque.
Two circular objects of different sizes that rotate together is a wheel and axle. Inclined plane wrapped around a central cylinder or bar to form a spiral is a screw.
gear or gears
Gears on a bike are a type of wheel and axle simple machine. As the pedals turn the circular motion into rotational motion, the gears on the bike increase or decrease the force needed to propel the bike forward.
Industrielle Anwendung von nicht-runden Zahnrädern
Set or Gears or Wheel and Axle
A gear is a simple machine, usually circular, with evenly cut teeth surrounding its perimeter. Spur gears are the most basic type and can be used in a wide variety of simple and complex machinery.
A machine with two circular devices of different sizes could be a gear system, where gears of varying diameters are used to transfer rotational motion or change the speed and torque of a mechanical system.
Gear are generally circular, with tooth. The number of tooth and their form are more important than is originally obvious.To provide technical benefits, getting in touch with gears have different variety of tooth.
gears, gears 2, and gears 3