Spur gears are the simplest, and probably most common, type of gear. Their general form is a cylinder or disk. The teeth project radially, and with these "straight-cut gears", the leading edges of the teeth are aligned parallel to the axis of rotation. These gears can only mesh correctly if they are fitted to parallel axles.
They connect parallel shafts, have involute teeth that are parallel to the shaft and can have internal or external teeth. They cause no external thrust between gears. They are inexpensive to manufacture and give lower but satisfactory performance. They are used when shaft rotates in the same plane. The main features of spur gears are dedendum, addendum, flank, and fillet. Dedendum cylinder is a root from where teeth extend, it extends to the tip called the addendum circle.
Material :carbon steel such as C45,20CrMnTi,40Cr,42CrMo or stainless steel or copper or nylon and so on Heat Treatment: Hardening and Tempering, High Frequency Quenching, Carburizing Quenching and so on. Standard: European