Cutting gear teeth: Slicing straight teeth can be comparatively easier than slicing helical teeth. Gear milling or gear hobbing can be used to cut the 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 necessary for cutting tooth of helical gear.
Influence load, vibration and sound: Since teeth of two mating spur gears comes in sudden contact, therefore they experience a shock or impact load. This also creates significant vibration and sound, which sometimes impose limit on optimum permissible speed of procedure. On the contrary, 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 quickness without much problem.
Contact situation between mating teeth: Spur gears have straight teeth parallel to gear axis. Two mating gears are also installed in parallel shafts. Thus teeth of two mating spur gears come in sudden get in touch with and the contact is always a line of size equals to teeth encounter width. On the other hand, helical gears have helical teeth plus they are installed on parallel shafts. So tooth of two mating helical gears can be found in gradual contact. Their engagement begins with a point 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 simple advantage of gear drive over other mechanical drives (like belt or chain drive) is its likelihood to use for non-parallel shafts. However, several types of gear are ideal for different orientations of driver and powered shafts. Both spur equipment and helical gears are overwhelmingly utilized for parallel shafts; whereas, bevel gears can be used for intersecting shafts and worm equipment can be used for perpendicular non-intersecting shafts. There is a particular kind of helical gear, called crossed helical equipment, which can be useful for transmitting power between perpendicular shafts. This is fairly similar to worm gear; however, crossed helical gear cannot offer high velocity reduction. Typically, it really is suitable for 1:1 to at least one 1:2 quickness ratio (when compared with 1:15 to at least one 1:100 in worm gear). Its application can be limited due to 
many limitations.