We can manufacture helical gears from 3mm diameter, up to 3 metre diameter.
Helical gears 0.3 mod thro 25 mod and all imperial equivalents.
Helical gears are so called because the angle of the teeth are inclined to the axis of the shafts in the form of a helix.
Helical gears are generally seen and described as high speed gears as they can take higher loads than equally sized spur gears. Also with a helical gear the two teeth start to engage and gradually increase as the gears rotate this gradual movement makes helical gears operate much more smoothly and quietly that spur gears. It’s because of this design that helical gears are used in the majority of transmissions.
The teeth on helical gears are cut at an angle to the face of the gear. When two teeth on a helical gear system engage, the contact starts at one end of the tooth and gradually spreads as the gears rotate, until the two teeth are in full engagement.
One interesting thing about helical gears is that if the angles of the gear teeth are correct, they can be mounted on perpendicular shafts, adjusting the rotation angle by 90 degrees.