Gear Nomenclature

Question 1

What is the apparent circle that two gears can be taken like smooth cylinders rolling without friction?

Answer 1

Pitch Circle

Question 2

What is the outer most profile circle of a gear?

Answer 2

Addendum Circle

Question 3

What is the radial distance between the pitch circle and the addendum circle?

Answer 3

Addendum

Question 4

What is the inner most profile circle?

Answer 4

Dedendum Circle

Question 5

What is the radial distance between the pitch circle and the dedendum circle?

Answer 5

Dedendum

Question 6

What is the radial distance from top of the tooth to the bottom of the tooth space in the mating gear?

Answer 6

Clearance

Question 7

What is the tangential space between teeth of mating gears at pitch circles?

Answer 7

Backlash

Question 8

What is the sum of the addendum and the dedendum?

Answer 8

Whole depth

Question 9

What is the length of tooth parallel to axes?

Answer 9

Face width

Question 10

What is the space in pitch circle used by each teeth?

Answer 10

Circular pitch

Question 11

What is the width of the tooth measured along the pitch circle?

Answer 11

Tooth thickness

Question 12

What is the width of space between the two adjacent teeth measured along the pitch circle?

Answer 12

Tooth space/Space width

Question 13

What is the surface at the bottom of a gear tooth space adjoining the fillet?

Answer 13

Bottom land

Question 14

What is the diameter of the pitch circle?

Answer 14

Pitch Diameter

Question 15

What is the total depth of a tooth space, equal to the addendum plus dedendum, also equal to working depth plus clearance?

Answer 15

Whole/full depth

Question 16

What is the depth of engagement of two gears, that is the sum of their addendums?

Answer 16

Working depth

Question 17

What is the surface of the top of the tooth?

Answer 17

Top land

Question 18

What is the surface of the tooth above the pitch surface?

Answer 18

Face of the tooth

Question 19

What is the concave portion of the tooth profile where it joins the bottom of the tooth space?

Answer 19

Fillet curve

Question 20

What is the approximate radius of the fillet curve?

Answer 20

Fillet radius

Question 21

What is the name of the shape of the curve that defines the flank of most modern gear teeth?

Answer 21

Involute

Question 22

What is the diameter of the outside circle?

Answer 22

Outside diameter

Question 23

What is the path of the contact in involute gears?

Answer 23

Line of action

Question 24

What is the angle between the common normal at the point of tooth contact and the common tangent to the pitch circle?

Answer 24

Pressure angle

The usual pressure angles are 14½° and 20°.

Question 25

What is a common point of contact between two pitch circles?

Answer 25

Pitch point

Question 26

What is the ratio of the arc of action to the circular pitch?

Answer 26

Contact ratio

Question 27

What is the distance traveled by a point on either pitch circle of the two wheels from the point of engagement to the pitch?

Answer 27

Arc of approach

Question 28

What is the distance traveled by a point on either pitch circle of the two wheels from the point to the point of disengagement?

Answer 28

Arc of recess

Question 29

What is the distance traveled by a point on either pitch circle of the two wheels during the period of contact of a pair of teeth?

Answer 29

Arc of contact

Question 30

What is the angle turned by a gear during arc of contact?

Answer 30

Angle of action

Question 31

What is the smaller gear of the two mating gears?

Answer 31

Pinion