Poormans “Hinge Bit”
Ever needed a cheaper way than buying an entire set of metal hinge bits for marking a center hole… you may have it in your junk drawers at home… This method centers a pen tip in a hinge hole.
Use a pen with a fat tip, and grind to the dimension you need for the hole in the hinge. This example shows a tip ground down about 1 mm. It’s plastic so you can just sandpaper, too.
Center the pen in the hole, click the pen, hold and push, and you get a mark where you can either drill or make the hole bigger with a punch.
Find a pen that is thick enough to fit your hinge hole, or grind it to the right size.
Put the tip into the hole, hold steady, and dispense the tip to make the mark in the correct center. Then use a punch or similar to increase the size of the hole, or just drill from the mark.