Making of Concentric Reducer

Not enough information disu. The internet is not a magic box.

Do you mean something like this:

i would like to make a concentric reducer by using a papper or plate

What is papper?

i would like to know the formula to make the reducer

What formula is there to know? Just manufacture it to the dimensions it needs to be.

sir i want tofabricate a concentric reducer in a 2mm plate i want to make lay out in the plate . is there any theory to mark in the plate?

Dimension thus:

D = larger diameter (as in Mikerho's drawing)

d = smaller diameter (C in same)

h = height of reducer (B in same)

Extend the upper and lower edges of the reducer until they meet at a vertex.

H = perpendicular distance of vertex from center of D; = Dh/(D-d).

R = slope distance of vertex to either end of D; = √[H² + (D/2)²].

r = slope distance of vertex to either end of d; = Rd/D.

Then the piece of metal you need is an annular sector of outer radius R, inner radius r, and angle 180D/H

[Ordinarily this would not be done via formulas. Instead one would use the drafting techniques for developments and intersections.]