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Profile of a spur gear Notation and numbering for an external gear Notation and numbering for an internal gear. The tooth surface (flank) forms the side of a gear tooth. [1] It is convenient to choose one face of the gear as the reference face and to mark it with the letter “I”. The other non-reference face might be termed face “II”.
Meshing of two spur gears with involute external teeth. z 1 = 20, z 2 = 50, α = 20°, ξ 1 = ξ 2 = 0, ISO 53:1998. The lower (green) gear is the driving one. The working (active) part of the line of action is shown in blue, which is the locus of all teeth contact points.
Gear teeth typically extend across the whole thickness of the gear. Another criterion for classifying gears is the general direction of the teeth across that dimension. This attribute is affected by the relative position and direction of the axes or rotation of the gears that are to be meshed together.
Spur gears can be classified into two main categories: External and Internal. Gears with teeth on the outside of the cylinder are known as "external gears". Gears with teeth on the internal side of the cylinder are known as "internal gears". An external gear can mesh with an external gear or an internal gear.
fig.1. A duplex worm or dual lead worm is a worm gear set where the two flanks are manufactured with slightly different modules and/or diameter quotients. As a result of this, different lead angles on both tooth profiles are obtained, so that the tooth thickness is continuously increasing all over the worm length, while the gap between two threads is decreasing.
Factors affecting the amount of backlash required in a gear train include errors in profile, pitch, tooth thickness, helix angle and center distance, and run-out. The greater the accuracy the smaller the backlash needed. Backlash is most commonly created by cutting the teeth deeper into the gears than the ideal depth.
This is the simplest form of bevel gear. It resembles a spur gear, only conical rather than cylindrical. The gears in the floodgate picture are straight bevel gears. In straight bevel gear sets, when each tooth engages, it impacts the corresponding tooth and simply curving the gear teeth can solve the problem.
A gear train or gear set is a machine element of a mechanical system formed by mounting two or more gears on a frame such that the teeth of the gears engage.. Gear teeth are designed to ensure the pitch circles of engaging gears roll on each other without slipping, providing a smooth transmission of rotation from one gear to the next. [2]