**Gear parameter interpretation**

**1)****What is “modulo”? **

Modulus indicates the size of the teeth.

Modulus is the ratio of the pitch pitch to the pi (π) in millimeters (mm).

In addition to the modulus, there are also CP (Circular pitch) and DP (diametral pitch).

The pitch is the length of the index arc between the equivalent points on the adjacent two teeth.

** ****2)****What is the “index circle diameter”? **

The index circle diameter is the reference diameter of the gear.

The two major factors determining the size of the gear are the modulus and the number of teeth,

The diameter of the division circle is equal to the product of the number of teeth and the modulus (end face).

In the past, the diameter of the index circle was called the reference pitch diameter. Recently, according to the ISO standard, it is collectively referred to as the index circle diameter.

**3)****What is the “pressure angle”? **

The acute angle between the radial line of the intersection of the tooth profile and the indexing circle and the toothed tangent of the point is called the indexing circle pressure angle. Generally speaking, the pressure angle refers to the indexing circle pressure angle.

The most commonly used pressure angle is 20°, but there are also gears that use pressure angles of 14.5°, 15°, 17.5°, and 22.5°.

**4)****What is the difference between a single head and a double head worm? **

The number of helical teeth of the worm is called the “number of heads”, which is equivalent to the number of teeth of the gear.

The more the number of heads, the larger the lead angle.

** ****5)****How do you distinguish between R (right-handed) and L (left-handed)? **

The gear shaft is laid flat on the vertical ground.

The right-handed gear is tilted to the right and the left-handed gear is tilted to the left.

**6) What is the difference between M****(modulo) and CP (weekly)? **

CP (Circular pitch) is the circumferential pitch on the indexing circle. The unit is the same as the modulus.

The CP is divided by the pi (π) to obtain M (modulus).

The relationship between M (modulo) and CP is as follows.

M (modulo)=CP/π (pi)

Both are units indicating the size of the teeth.

**7)****What is “backlash”? **

A gap between the tooth faces when a pair of gears are engaged.

The backlash is a necessary parameter for the smooth meshing of the gears.

** ****8)****What is the difference between bending strength and tooth surface strength? **

The strength of the gear should generally be considered in terms of both bending and tooth surface strength.

The bending strength is the strength of the gear teeth that transmit power due to the bending force, and the teeth are broken at the root of the tooth.

The tooth surface strength is the anti-friction strength of the tooth surface in the repeated contact of the engaged teeth.

**9)****Bending strength and tooth strength****,****Which strength is used as the basis for selecting the gear it is good? **

In general, it is necessary to discuss the strength of the bend and the flank at the same time.

However, when a gear, a manual gear, or a low-speed meshing gear that is used less frequently is selected, it is selected only by the bending strength. Ultimately, it should be up to the designer.

**10)****What is the “center distance”? **

Center distance is the distance between the axes of a pair of gears.

The size of the center distance affects the backlash.

The larger the center distance, the larger the backlash.

**11)****The tolerance of the center of the spur gear is****,****How much should I take in general? **

Generally, the reference value is approximately ± tolerance of 0.

**12)****What is the “axis angle”? **

The angle between the intersecting shaft gear (the bevel gear) and the crossed shaft gears (the staggered shaft helical gear and the worm gear). Usually 90°.

The size of the intersection angle is an important factor in the tooth contact and backlash.

**13)****What is the “assembly distance”? **

The axial distance from the conical apex of the bevel gear to the locating surface (mounting plane).

Assembly distance is an important size that affects tooth contact and backlash.