GEAR TERMINOLOGY AND PARAMETER

GEARS ARE ANONYMOUS PART OF ENGINEERING AND IT IS IMPORTANT TO KNOW WHAT ARE VARIOUS PARAMETERS RELATING TO IT.


When two gears mate then we refer term gear for the larger gear and term pinion for smaller gear.




LIST OF DEFINATIONS RELATED TO GEAR TEETH:-

1) PITCH CIRCLE

It is circle which is responsible for tooth profile. All the tooth parameter like addendum or dedendum are established from pitch circle only.

2) ADDENDUM

It is the height of the tool above the pitch circle. In figure it is denoted by (a).

3) ADDENDUM CIRCLE

It is the circle formed by the considering an imaginary line formed by touching the top most part of the gear teeth (top land).

4) DEDENDUM

It is the depth of the gear tooth below the pitch circle. It is denoted by (b).

5) DEDENDUM CIRCLE

It is the circle formed by considering an imaginary lines formed by touching the bottom most part ( root of tooth ) of the gears teeth.

6) TOTAL DEPTH OF GEAR TEETH

It is summation of addendum and dedendum. It denotes the total working space for mating gears.

7) FACE WIDTH

In simple language it is the broadness of the the gear teeth or in other words it is the thickness of the teeth. In engineering terminology it it is the length of gear tooth along the axes.

8) DIAMETRAL PITCH

It is the ratio of number of teeth to the pitch circle diameter. It can also said that diametrical pitch is number of teeth per unit volume.
                                            NUMBER OF TEETH
DIA PITCH (DP) =       __________________________
                                       PITCH CIRCLE DIAMETER

9) MODULE

It is inverse of diametral pitch (1/DP). It is ratio of pitch circle diameter to the number of teeth.


                                     PITCH CIRCLE DIAMETER
MODULE (M) =       __________________________
                                       NUMBER OF TEETH

10) GEAR RATIO

It is the ratio of largest gear teeth to smallest gear gear teeth.
Suppose N1 is the larger gear and N2 is the smaller gear, then gear ratio is (N1/N2).

11) BACKLASH

At pitch circle, the tangential space between mating gear teeth is called backlash.

12) PITCH ANGLE

The angle captured by single tooth is called pitch angle which is given by ( 360/ T).

13) COMMAN TANGENT

It is the comman tangent line which touches both the mating gears at pitch circle.

14) TOP LAND

As clearly specified in figure, it is the upper face of gear teeth.

15) BOTTOM LAND

It is the clearance area provided after each tooth where the top land of mating gear teeth affixes.

16) CIRCULAR THICKNESS

It is the thickness of gear at the pitch circle diameter.

17) FILLET

It is small angle given to each tooth at bottom or root of each tooth for proper and stress free mating.


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