Question 204012
this is either a very large flange using 4 1/2 " bolts, or a small flange with a 4.5" bolt circle ___ let's assume small


the radius of the bolt circle is 2.25" (half the diameter}


a triangle is formed by two adjacent holes and the center of the flange opening


this is an isosceles triangle with a vertex angle of 45º (1/8 of 360º) and a side length of 2.25"


the distance between centers is the base (b) of the triangle


using trigonometry ___ b/2 = 2.25 [sin(22.5º)] ___ b = 1.72" (approx)