Have you ever wondered how to find the centre of a disc? There are a few tools out there to help you but I have found this simple method to be very easy. All you need is a see through template that has a grid printed on it. I had this one left over from my patchworking days. I drilled a hole where the lines intersect then placed the disc underneath the template lining up the sides withing the grid markings.
With a Sharpie pen, draw a mark through the hole that you have drilled.
Voila! You have now marked the centre point of your round disc :)