what is PCD? How to calculate the distance between the two adjacent holes?

What is PCD?

         It is called pitch circle diameter, is also called bolt circle diameter. The center of each holes or bolts that are passing on a circumference of a circle. It is the circle on which the holes are going to be done. 

EXAMPLE:

8 holes to be equally in a 200 mm pitch circle then the division; a =dia×0.3827 

=200×0.3827 

=76.54 mm

1.FOR THREE HOLES:

No. of hole on the pitch circle	Diagram	Formula
3 Holes		A= pcd×0.66

                       

            The total degree of the circle=360

            If we form a triangle joining the center of the circle and the center of the two Adjacent holes as shown in the figure,

            We could see the adjacent sides of the triangle forms degree θ and if we divide the triangle into    two it forms a right angle triangle with𝜃/ 2  degree.

θ = 360°/3 

θ/2 =60° 

           We know that for a right angle triangle,

                               sin θ=Opposite side/Hypotenuse side

                                    sin θ/2=(a/2)/r

                                    sin 60°=a/2r =  a/d

                                    0.866 =a/d

                                    a=d 0.866

           Here d means pitch circle diameter. So the distance between the two adjacent holes, a=pcd 0.866

2.FOR FOUR HOLES:

No. of hole on the pitch circle	Diagram	Formula
4 Holes		A= pcd×0.7071

                                           

                                    

The total degree of the circle=360

            If we form a triangle joining the center of the circle and the center of the two Adjacent holes as shown in the figure,

            We could see the adjacent sides of the triangle forms degree θ and if we divide the triangle into    two it forms a right angle triangle with  𝜃/ 2 degree.

θ = 360°/4 

θ/2 =45°

           We know that for a right angle triangle,

                              sin θ=Opposite side/Hypotenuse side

                                    sin θ/2=(a/2)/r

                                    sin 45°=a/2r =  a/d

                                    0.7071 =a/d

                                    a=d 0.7071

           Here d means pitch circle diameter.So the distance between the two adjacent holes a= pcd0.7071

3.FOR FIVE HOLES:

No. of hole on the pitch circle	Diagram	Formula
5 Holes		A= pcd× 0.5878

                                           

                             

    The total degree of the circle=360

            If we form a triangle joining the center of the circle and the center of the two Adjacent holes as shown in the figure,

            We could see the adjacent sides of the triangle forms degree θ and if we divide the triangle into    two it forms a right angle triangle with𝜃/ 2  degree.

θ = 360°/5 

θ/2 =36°

           We know that for a right angle triangle,

                               sin θ=Opposite side/Hypotenuse side

                                    sin θ/2=(a/2)/r

                                    sin 36°=a/2r =  a/d

                                    0.5878 =a/d

                                    a=d 0.5878

           Here d means pitch circle diameter.So the distance between the two adjacent holes,a=pcd 0.5878

4.FOR SIX HOLES:

No. of hole on the pitch circle	Diagram	Formula
6 Holes		A= pcd×0.5

                                  

 The total degree of the circle=360

            If we form a triangle joining the center of the circle and the center of the two Adjacent holes as shown in the figure,

            We could see the adjacent sides of the triangle forms degree θ and if we divide the triangle into    two it forms a right angle triangle with𝜃/ 2  degree.

θ = 360°/6 

θ/2 =30° 

           We know that for a right angle triangle,

                               sin θ=Opposite side/Hypotenuse side

                                    sin θ/2=(a/2)/r

                                    sin 30°=a/2r =  a/d

                                   0.5 =a/d

                                    a=d 0.5

           Here d means pitch circle diameter. So the distance between the two adjacent holes, a=pcd 0.5

5.FOR SEVEN HOLES:

No. of hole on the pitch circle	Diagram	Formula
7 Holes		A= pcd×0.4339

 
                             

The total degree of the circle=360

            If we form a triangle joining the center of the circle and the center of the two Adjacent holes as shown in the figure,

            We could see the adjacent sides of the triangle forms degree θ and if we divide the triangle into    two it forms a right angle triangle with𝜃/ 2  degree.

θ = 360°/7

θ/2 =25.7143°

           We know that for a right angle triangle,

                             sin θ=Opposite side/Hypotenuse side

                                    sin θ/2=(a/2)/r

                                    sin 25.7143°=a/2r =  a/d

                                    0.4339 =a/d

                                    a=d 0.4339

           Here d means pitch circle diameter.So the distance between the two adjacent holes,a=pcd 0.4339

6.FOR EIGHT HOLES:

No. of hole on the pitch circle	Diagram	Formula
8 Holes		A= pcd× 0.3827

        

 The total degree of the circle=360

            If we form a triangle joining the center of the circle and the center of the two Adjacent holes as shown in the figure,

            We could see the adjacent sides of the triangle forms degree θ and if we divide the triangle into    two it forms a right angle triangle with𝜃/ 2  degree.

θ = 360°/8 

θ/2 =22.5° 

           We know that for a right angle triangle,

                               sin θ=Opposite side/Hypotenuse side

                                    sin θ/2=(a/2)/r

                                    sin 22.5°=a/2r =  a/d

                                   0.3827 =a/d

                                    a=d 0.3827

           Here d means pitch circle diameter.So the distance between the two adjacent holes,a=pcd 0.3827 

7.FOR NINE  HOLES:

No. of hole on the pitch circle	Diagram	Formula
9 Holes		A= pcd×0.342

 The total degree of the circle=360

            If we form a triangle joining the center of the circle and the center of the two Adjacent holes as shown in the figure,

            We could see the adjacent sides of the triangle forms degree θ and if we divide the triangle into    two it forms a right angle triangle with𝜃/ 2  degree.

θ = 360°/9 

θ/2 =20°

           We know that for a right angle triangle,

                                    sin θ=Opposite side/Hypotenuse side

                                    sin θ/2=(a/2)/r

                                    sin 20°=a/2r =  a/d

                                    0.342 =a/d

                                    a=d 0.342

           Here d means pitch circle diameter. So the distance between the two adjacent holes, a=pcd 0.342

8.FOR TEN HOLES:

No. of hole on the pitch circle	Diagram	Formula
10 Holes		A= pcd×0.309

             

The total degree of the circle=360

            If we form a triangle joining the center of the circle and the center of the two Adjacent holes as shown in the figure,

            We could see the adjacent sides of the triangle forms degree θ and if we divide the triangle into    two it forms a right angle triangle with𝜃/ 2  degree.

θ = 360°/10

θ/2 =18°

           We know that for a right angle triangle,

                           sin θ=Opposite side/Hypotenuse side

                                    sin θ/2=(a/2)/r

                                    sin 18°=a/2r =  a/d

                                    0.309 =a/d

                                    a=d 0.309

           Here d means pitch circle diameter. So the distance between the two adjacent holes, a=pcd 0.309