Cutting gear teeth: Trimming straight teeth is certainly comparatively easier than cutting helical teeth. Equipment milling or equipment hobbing can be used to cut tooth of spur and helical gears. In milling, only two simultaneous motions are wanted to cut the teeth of spur gears; nevertheless, three simultaneous motions are necessary for cutting the teeth of helical gear.
Impact load, vibration and noise: Since teeth of two mating spur gears will come in sudden contact, therefore they encounter a shock or effect load. This also creates significant vibration and sound, which occasionally impose limit on maximum 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 quickness without much problem.
Contact situation between mating teeth: Spur gears have straight teeth parallel to equipment axis. Two mating gears are also mounted in parallel shafts. Thus teeth of two mating spur gears come in sudden contact and the get in touch with is always a line of duration equals to teeth encounter 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 get in touch with. Their engagement starts with a point and becomes a 
line and then steadily 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 its probability to use for non-parallel shafts. However, various kinds gear are suitable for varying orientations of driver and driven shafts. Both spur gear 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 exists a particular kind of helical gear, called crossed helical gear, 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 decrease. Typically, it is suitable for 1:1 to at least one 1:2 speed ratio (as compared to 1:15 to at least one 1:100 in worm gear). Its application is also limited because of many limitations.