We need the radius of the circle so we can use it with
the drafting compass.
Returning to your highschool math, the equation for calculating
the circumference of a circle is
We know the circumference (c) is 190mm and we know
pi is 3.14, so if we flip-flop the equation we get
= c/2(3.14) or 190/6.28 = 30mm
Set your compass along your ruler, from point to pencil tip,
at 30mm and draw a circle
in the middle of a sheet of practice paper. This is your baseline.
*I'll be darned if I can get pi to show up in html!