Review on Precision Measuring with Woodworking Caliber Marking Degrees by Rob Parsons

When this center finder arrived I figured I could just assemble it, mark the center of my circle and all would be fine. However, after the first use, I found that they did NOT match exactly. After using it twice, I found that the lines didn't intersect, which is necessary to find the center. This means that the ruler built into the device is not exactly square. So I took out my framing triangle and saw that the ruler was slightly offset. But by loosening and tightening four screws I was able to make it square. After that, the lines intersected on the circle. So buy this, but understand that it will require some tweaking to make it work properly.