A centre finder is a common tool that allow you to find the centre of any cylindrical thing. The more round it is, the more precise will be the centre finder. On a log or any not totaly cylindrical thing you will draw multiple lines and be able to find an aproximative centre.
The Serious Centre Finder is a trustable tool you can use at its original size to find centre of parts until a diameter of 254mm (10"). It's built strong to never bend in use and its reference corners are heavy duty. The tool have a beweled marking edge to allow a very precise drawing line. It's a lifetime tool.
Best print : 0.3mm Nozzle, 0.2 layers, 4 walls, 6 layers for top and bottom
Don't be cheap with infill. Print a lifetime tool. Prefer PLA and avoid any softer material.
Don't try to clean the part, you can unstraight the part. If your printer is properly calibrated, you don't need anything, even if the first layer is too much squeeze out.
My old wooden centre finder just was no more acurate.
I downloaded all centre finders I could found on Thingiverse. To be honnest, I was in a middle of a project and in hurry to find the centre of a wooden cylindre. I wasted a lot time to print unusable centre finders. Too small, too soft, bendable... Well I get a bit upset, none was realy usable trusty tools.
So I opened my CAD program to redesign the wooden centre finder I made with my dad by the past. I undersized the lenght because I never had to used mine over very large pieces, and I wanted it to be printable on any standard printer. I oversized the walls to get a strong tool even if out of plastic. I also kept one very usefull feature : the bewel marking area which is very comfortable and accurate when you draw lines.
When I designed it, this was the only Serious Centre Finder you can find on Thingiverse. If you don't own a centre finder, just print it out, keep it for life time, you'll be happy to have it on your shelf.