Cutting gear teeth: Reducing straight teeth is certainly comparatively easier than reducing helical teeth. Gear milling or equipment hobbing can be used to cut teeth of spur and helical gears. In milling, only two simultaneous motions are wanted to cut teeth of spur gears; however, three simultaneous motions are necessary for cutting teeth of helical gear.
Impact load, vibration and noise: Since teeth of two mating spur gears will come in sudden contact, so they experience a shock or influence load. This also creates significant vibration and noise, which occasionally impose limit on optimum permissible speed of operation. On the other hand, gradual contact between mating teeth outcomes a gradual load on one’s teeth and lower vibration and noise. Thus helical gears can be employed at higher velocity without much problem.
Contact scenario between mating teeth: Spur gears have directly teeth parallel to gear axis. Two mating gears are also installed in parallel shafts. Thus teeth of two mating spur gears come in sudden contact and the contact is always a line of length equals to teeth encounter width. On the other hand, helical gears have helical teeth and they are installed on parallel shafts. So tooth of two mating helical gears come in gradual contact. Their engagement begins with a point and becomes a series and then gradually disengages as a point. So contact length will not remain constant.
Orientation of driver and driven shafts: One basic advantage of equipment drive over other mechanical drives (like belt or chain drive) is the probability to use for non-parallel shafts. However, various kinds gear are suitable for different orientations of driver and powered shafts. Both spur gear and helical gears are overwhelmingly utilized for parallel shafts; whereas, bevel gears can be used for intersecting shafts and worm gear can be utilized for perpendicular nonintersecting shafts. There is a particular kind of helical equipment, called crossed helical equipment, which can be employed for transmitting power between perpendicular shafts. This is fairly similar to worm gear; however, crossed helical gear cannot provide high velocity reduction. Typically, it really is suitable for 1:1 to at least one 1:2 velocity ratio (as compared to 1:15 to 1 1:100 in worm gear). Its application can be limited due to many limitations.