Spiral Bevel Gear
Spiral bevel gears will be bevel gears with curved tooth lines. Because of higher tooth contact ratio, they are more advanced than straight bevel gears in performance, strength, vibration and sound. Alternatively, they are more difficult to produce. Also, as the teeth are curved, they cause thrust forces in the axial path. Within the spiral bevel gears, the one with the zero twisting position is named zerol bevel gear.
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Bevel Gear
Bevel gears have a cone shaped appearance and are being used to transmit force between two shafts which intersect in one point (intersecting shafts). A bevel gear includes a cone as its pitch area and its teeth are minimize along the cone. Sorts of bevel gears consist of right bevel gears, helical bevel gears, spiral bevel gears, miter gears, angular bevel gears, crown gears, 
zerol bevel gears and hypoid gears.
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Gear Rack
Same sized and shaped teeth cut at equal distances along a flat surface or a direct rod is named a gear rack. A gear rack is a cylindrical equipment with the radius of the pitch cylinder simply being infinite. By meshing with a cylindrical gear pinion, it converts rotational action into linear motion. Gear racks could be broadly divided into direct tooth racks and helical tooth racks, but both have got right tooth lines. By machining the ends of equipment racks, you’ll be able to connect equipment racks end to end.
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Helical Gear
Helical gears are being used with parallel shafts related to spur gears and are cylindrical gears with winding tooth lines. They possess better pearly whites meshing than spur gears and have superior quietness and will transmit bigger loads, making them suitable for high speed applications. When working with helical gears, they create thrust induce in the axial way, necessitating the utilization of thrust bearings. Helical gears include right hand and left hands twist requiring opposite side gears for a meshing set.
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