Cutting gear teeth: Slicing straight teeth is definitely comparatively easier than reducing helical teeth. Gear milling or gear hobbing can be utilized to cut tooth of spur and helical gears. In milling, just two simultaneous motions are desired to cut teeth of spur gears; nevertheless, three simultaneous motions are necessary for cutting teeth of helical gear.
Influence load, vibration and sound: Since teeth of two mating spur gears will come in sudden contact, so they experience a shock or influence load. This also generates significant vibration and noise, which occasionally impose limit on maximum 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 swiftness without much problem.
Contact scenario between mating teeth: Spur gears have directly teeth parallel to equipment axis. Two mating gears are also installed in parallel shafts. Thus the teeth of two mating spur gears can be found in sudden get in touch with and the get in touch with is always a type of length equals to teeth encounter width. On the other hand, helical gears possess helical teeth plus they are installed on parallel shafts. So tooth of two mating helical gears come in gradual get in touch with. Their engagement starts with a point and becomes a series and then steadily disengages as a point. So contact length will not remain constant.
Orientation of driver and driven shafts: One fundamental advantage of equipment drive over other mechanical drives (like belt or chain drive) is the likelihood to use for non-parallel shafts. However, several types of gear are suitable for varying orientations of driver and driven shafts. Both spur gear and helical gears are overwhelmingly used 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 type of helical gear, called crossed helical gear, which can be useful for transmitting power between perpendicular shafts. This is quite similar to worm equipment; however, crossed helical equipment cannot provide high velocity reduction. Typically, it really is suitable for 1:1 to 1 1:2 speed ratio (when compared with 1:15 to at least one 1:100 in worm gear). Its application is also limited because of many limitations.