Spur gears are the most easily visualized common gears that transmit movement between two parallel shafts. Because of the shape, they are categorized as a type of cylindrical gears. Because the tooth surfaces of the gears are 
parallel to the axes of the installed shafts, there is no thrust force generated in the axial direction. Also, because of the simple production, these gears can be made to a high degree of precision. On the other hand, spur gears have a disadvantage for the reason that they quickly make noise. Generally speaking, when two spur gears are in mesh, the gear with more the teeth is called the “gear” and the main one with the smaller number of teeth is named the “pinion”.
The unit to point the sizes of spur gears is often stated, as specified by ISO, to be “module”. Recently, it is normal to create the pressure position to 20 degrees. In commercial machinery, it is most common to employ a part of an involute curve as the tooth profile.
Even though not limited by spur gears, profile shifted gears are utilized when it is required to adjust the center distance slightly or even to strengthen the gear teeth. They are produced by adjusting the distance between your gear cutting tool called the hobbing tool and the apparatus in the production stage. When the shift is certainly positive, the bending power of the apparatus increases, while a poor shift slightly reduces the center distance. The backlash may be the play between the teeth when two gears are meshed and is necessary for the easy rotation of gears. When the backlash can be too large, it leads to increased vibration and noise while the backlash that’s too little leads to tooth failure due to the lack of lubrication.
All KHK spur gears possess an involute tooth shape. Quite simply, they are involute gears using area of the involute curve as their tooth forms. Searching generally, the involute form is the most wide-spread gear tooth form due to, among other factors, the capability to absorb small center distance errors, quickly made production tools simplify manufacturing, thicker roots of the teeth make it strong, etc. Tooth form is often referred to as a specification in drawing of a spur equipment as indicated by the Screw Vacuum Pumps height of teeth. In addition to standard full depth teeth, extended addendum and stub tooth profiles exist.