Cutting gear teeth: Slicing straight teeth is comparatively easier than slicing helical teeth. Gear milling or equipment hobbing can be utilized to cut tooth of spur and helical gears. In milling, just two simultaneous motions are desired to cut the teeth of spur gears; however, three simultaneous motions are required for cutting the 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 impact load. This also generates significant vibration and sound, which occasionally impose limit on maximum permissible speed of operation. On the contrary, gradual get in touch with between mating teeth outcomes a gradual load on the teeth and lower vibration and noise. Thus helical gears may be employed at higher velocity without much problem.

Contact situation between mating teeth: Spur gears have directly teeth parallel to gear axis. Two mating gears are also mounted in parallel shafts. Thus the teeth of two mating spur gears can be found in sudden get in touch with and the contact is always a line of size equals to teeth encounter width. On the contrary, helical gears possess helical teeth plus they are installed on parallel shafts. So the teeth of two mating helical gears come in gradual get in touch with. Their engagement begins with a spot and becomes a range and then gradually disengages as a point. So contact length does 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 nonparallel shafts. However, several types of gear are suitable for various orientations of driver and powered shafts. Both spur equipment and helical gears are overwhelmingly used for parallel shafts; whereas, bevel gears can be used for intersecting shafts and worm equipment can be utilized for perpendicular non-intersecting 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 equipment; however, crossed helical equipment cannot offer high velocity reduction. Typically, it is suitable for 1:1 to 1 1:2 quickness ratio (as compared to 1:15 to 1 1:100 in worm gear). Its application is also limited due to many limitations.