Spur gears will be the most easily visualized common gears that transmit motion between two parallel shafts. Because of the shape, they are classified as a type of cylindrical gears. Because the tooth areas of the gears are parallel to the axes of the mounted shafts, there is no thrust force generated in the axial direction. Also, due to the ease of production, these gears could be made to a higher degree of precision. On the other hand, spur gears have a disadvantage for the reason that they very easily make noise. In most cases, when two spur gears are in mesh, the apparatus with more the teeth is named the “equipment” and the one with small number of teeth is called the “pinion”.

The unit to indicate the sizes of spur gears is often stated, as specified by ISO, to be “module”. Recently, it is normal to create the pressure angle to 20 degrees. In commercial machinery, it is most common to use a part of an involute curve as the tooth profile.

Even though not really limited by spur gears, profile shifted gears are used when it is required to adjust the guts distance slightly or even to strengthen the gear teeth. They are made by adjusting the range between your gear cutting tool called the hobbing device and the gear in the production stage. When the change is definitely positive, the bending power of the gear increases, while a poor shift slightly reduces the guts distance. The backlash may be the play between the tooth when two gears are meshed and is necessary for the even rotation of gears. When the backlash is usually too big, it leads to increased vibration and noise while the backlash that is too small leads to tooth failing because of the lack of lubrication.

All KHK spur gears have an involute tooth shape. In other words, they are involute gears using area of the involute curve as their tooth forms. Searching generally, the involute shape is the most wide-spread equipment tooth form due to, among other reasons, the ability to absorb small center distance errors, quickly made production tools simplify V Belt Pulley manufacturing, thick 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 height of teeth. Furthermore to standard complete depth teeth, prolonged addendum and stub tooth profiles exist.