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In spur and helical gears, unless otherwise specified, the standard pitch diameter is related to the number of teeth and the standard transverse pitch. Standard reference pitch diameter can be estimated by taking average of gear teeth tips diameter and gear teeth base diameter.
In the case of Module (MOD) 4.0 spur gears: Normal spur gears (over 17 teeth) have a pitch circle diameter (PCD) equal to MOD × number of teeth. [4] Corrected spur gears (under 17 teeth) have a PCD equal to MOD × number of teeth + MOD. There are two types of corrected gears: S0 gearing (x1 + x2 = zero) S gearing (x1 + x2 ≠ zero)
Module is a direct dimension ("millimeters per tooth"), unlike diametral pitch, which is an inverse dimension ("teeth per inch"). Thus, if the pitch diameter of a gear is 40 mm and the number of teeth 20, the module is 2, which means that there are 2 mm of pitch diameter for each tooth. [56]
An automotive belt with the number "740K6" or "6K740" indicates a belt 74 inches (190 cm) in length, 6 ribs wide, with a rib pitch of 9 ⁄ 64 of an inch (3.6 mm) (a standard thickness for a K series automotive belt would be 4.5mm). A metric equivalent would be usually indicated by "6PK1880" whereby 6 refers to the number of ribs, PK refers to ...
A belt drive is analogous to that of a chain drive; however, a belt sheave may be smooth (devoid of discrete interlocking members as would be found on a chain sprocket, spur gear, or timing belt) so that the mechanical advantage is approximately given by the ratio of the pitch diameter of the sheaves only, not fixed exactly by the ratio of ...
Pressure angles. Pressure angle in relation to gear teeth, also known as the angle of obliquity, [1] is the angle between the tooth face and the gear wheel tangent. It is more precisely the angle at a pitch point between the line of pressure (which is normal to the tooth surface) and the plane tangent to the pitch surface.
Meshing of two spur gears with involute external teeth. z 1 = 20, z 2 = 50, α = 20°, x 1 = x 2 = 0, ISO 53:1998. The lower (green) gear is the driving one. The line of contact, which is the locus of all teeth contact points, is shown in blue.
The same involute gear may be used under conditions that change its operating pitch diameter and pressure angle. Unless there is a good reason for doing otherwise, it is practical to consider that the pitch and the profile angle of a single gear correspond to the pitch and the profile angle of the hob or cutter used to generate its teeth.