Cutting gear teeth: Reducing straight teeth is certainly comparatively easier than cutting helical teeth. Equipment milling or gear hobbing can be utilized to cut teeth of spur and helical gears. In milling, only two simultaneous motions are desired to cut tooth of spur gears; nevertheless, three simultaneous motions are required for cutting teeth of helical gear.
Impact load, vibration and noise: Since teeth of two mating spur gears comes in sudden contact, therefore they experience a shock or impact load. This also generates significant vibration and sound, which sometimes impose limit on maximum permissible speed of procedure. On the other hand, gradual get in touch with between mating teeth results a gradual load on the teeth and lower vibration and noise. Thus helical gears can be employed at higher velocity without much problem.
Contact situation between mating teeth: Spur gears have directly teeth parallel to equipment axis. Two mating gears are also mounted in parallel shafts. Thus teeth of two mating spur gears can be found in sudden get in touch with and the get in touch with is always a line of length equals to teeth face width. On the contrary, helical gears have helical teeth plus they are mounted on parallel shafts. So teeth of two mating helical gears can be found in gradual contact. Their engagement starts with a point and becomes a line and then gradually disengages as a point. So contact length will not remain constant.
Orientation of driver and driven shafts: One simple advantage of equipment drive over other mechanical drives (like belt or chain drive) is its possibility to use for nonparallel 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 utilized for intersecting shafts and worm gear can be used for perpendicular non-intersecting shafts. There exists a particular type of helical gear, called crossed helical gear, which can be useful for transmitting power between perpendicular shafts. This is very similar to worm gear; however, crossed helical equipment cannot provide high velocity reduction. Typically, it is suitable for 1:1 to at least one 1:2 rate ratio (in comparison with 1:15 to at least one 1:100 in worm gear). Its application can be limited because of many limitations.