naruto

It will work but it can be off by a BIG margin That method is called tangent... now i don't know if anyone here has tried to make a line tangent to a circle but if you aren't tangent to one of the circles sides you will NOT be on center... Bisecting a chord is the best way to find the diameter and the most accurate...

First draw a line through the circle where the line hits the outer circle on the left we will call it A and the right we will call it B Now Take a compass open it so it is wider then half the line you just drew.. Place the compass on point A and strike a half circle through the line Place the compass on point B and strike a half circle through the line causing it to cross with the other half circle from point A Now where the two half circles cross grab a ruler and line up the two cross points (one intersection will be above the line and one will be below) and draw a line.... That line is the diameter... I'm pretty sure you can get the cross section of that diameter